Condensed Matter
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Showing new listings for Friday, 22 November 2024
- [1] arXiv:2411.13563 [pdf, html, other]
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Title: Dynamical modes of highly elastic loops settling under gravity in a viscous fluidComments: 26 pagesSubjects: Soft Condensed Matter (cond-mat.soft)
The settling of highly elastic non-Brownian closed fibres (called loops) under gravity in a viscous fluid is investigated numerically. The loops are represented using a bead-spring model with harmonic bending potential and finitely extensible nonlinear elastic (FENE) stretching potential. Numerical solutions to the Stokes equations are obtained with the use of HYDROMULTIPOLE numerical codes, which are based on the multipole method corrected for lubrication to calculate hydrodynamic interactions between spherical particles with high precision. Depending on the elasto-gravitation number B, a ratio of gravitation to bending forces, the loop approaches different attracting dynamical modes, as described by Gruziel-Slomka et al. (Soft Matter, vol. 15, 2019, pp. 7262-7274) with the use of the Rotne-Prager mobility of the elastic loop made of beads. Here, using a more precise method, we find and characterise a new mode, analyse typical timescales, velocities, and orientations of all the modes, compare them, and investigate their coexistence. We analyse the transitions (bifurcations) to a different mode at certain critical values of the elasto-gravitation number B.
- [2] arXiv:2411.13606 [pdf, html, other]
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Title: The stabilizing role of multiplicative noise in non-confining potentialsComments: 14 pages, 8 figuresSubjects: Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph); Statistics Theory (math.ST); Adaptation and Self-Organizing Systems (nlin.AO)
We provide a simple framework for the study of parametric (multiplicative) noise, making use of scale parameters. We show that for a large class of stochastic differential equations increasing the multiplicative noise intensity surprisingly causes the mass of the stationary probability distribution to become increasingly concentrated around the minima of the multiplicative noise term, whilst under quite general conditions exhibiting a kind of intermittent burst like jumps between these minima. If the multiplicative noise term has one zero this causes on-off intermittency. Our framework relies on first term expansions, which become more accurate for larger noise intensities. In this work we show that the full width half maximum in addition to the maximum is appropriate for quantifying the stationary probability distribution (instead of the mean and variance, which are often undefined). We define a corresponding new kind of weak sense stationarity. We consider a double well potential as an example of application, demonstrating relevance to tipping points in noisy systems.
- [3] arXiv:2411.13625 [pdf, other]
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Title: Partition function approach to non-Gaussian likelihoods: information theory and state variables for Bayesian inferenceRebecca Maria Kuntz, Heinrich von Campe, Tobias Röspel, Maximilian Philipp Herzog, Björn Malte SchäferSubjects: Statistical Mechanics (cond-mat.stat-mech); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
The significance of statistical physics concepts such as entropy extends far beyond classical thermodynamics. We interpret the similarity between partitions in statistical mechanics and partitions in Bayesian inference as an articulation of a result by Jaynes (1957), who clarified that thermodynamics is in essence a theory of information. In this, every sampling process has a mechanical analogue. Consequently, the divide between ensembles of samplers in parameter space and sampling from a mechanical system in thermodynamic equilibrium would be artificial. Based on this realisation, we construct a continuous modelling of a Bayes update akin to a transition between thermodynamic ensembles. This leads to an information theoretic interpretation of Jazinsky's equality, relating the expenditure of work to the influence of data via the likelihood. We propose one way to transfer the vocabulary and the formalism of thermodynamics (energy, work, heat) and statistical mechanics (partition functions) to statistical inference, starting from Bayes' law. Different kinds of inference processes are discussed and relative entropies are shown to follow from suitably constructed partitions as an analytical formulation of sampling processes. Lastly, we propose an effective dimension as a measure of system complexity. A numerical example from cosmology is put forward to illustrate these results.
- [4] arXiv:2411.13629 [pdf, html, other]
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Title: Generalization of the Gauss Map: A jump into chaos with universal featuresComments: accepted for publication in PRESubjects: Statistical Mechanics (cond-mat.stat-mech); Chaotic Dynamics (nlin.CD)
The Gauss map (or continued fraction map) is an important dissipative one-dimensional discrete-time dynamical system that exhibits chaotic behaviour and which generates a symbolic dynamics consisting of infinitely many different symbols. Here we introduce a generalization of the Gauss map which is given by $x_{t+1}=\frac{1}{x_t^\alpha} - \Bigl[\frac{1}{x_t^\alpha} \Bigr]$ where $\alpha \geq 0$ is a parameter and $x_t \in [0,1]$ ($t=0,1,2,3,\ldots$). The symbol $[\dots ]$ denotes the integer part. This map reduces to the ordinary Gauss map for $\alpha=1$. The system exhibits a sudden `jump into chaos' at the critical parameter value $\alpha=\alpha_c \equiv 0.241485141808811\dots$ which we analyse in detail in this paper. Several analytical and numerical results are established for this new map as a function of the parameter $\alpha$. In particular, we show that, at the critical point, the invariant density approaches a $q$-Gaussian with $q=2$ (i.e., the Cauchy distribution), which becomes infinitely narrow as $\alpha \to \alpha_c^+$. Moreover, in the chaotic region for large values of the parameter $\alpha$ we analytically derive approximate formulas for the invariant density, by solving the corresponding Perron-Frobenius equation. For $\alpha \to \infty$ the uniform density is approached. We provide arguments that some features of this transition scenario are universal and are relevant for other, more general systems as well.
- [5] arXiv:2411.13638 [pdf, html, other]
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Title: Variational approach to the dynamics of dissipative quantum impurity modelsYi-Fan Qu, Martino Stefanini, Tao Shi, Tilman Esslinger, Sarang Gopalakrishnan, Jamir Marino, Eugene DemlerComments: 18 pages, 7 figuresSubjects: Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el)
Recent experiments with quantum simulators using ultracold atoms and superconducting qubits have demonstrated the potential of controlled dissipation as a versatile tool for realizing correlated many-body states. However, determining the dynamics of dissipative quantum many-body systems remains a significant analytical and numerical challenge. In this work, we focus on a dissipative impurity problem as a testbed for new methodological developments. We introduce an efficient non-perturbative framework that combines the superposition of Gaussian states (SGS) variational ansatz with the quantum trajectory approach to simulate open systems featuring a dissipative impurity. Applying this method to a spinful impurity subject to two-body losses and embedded in a bath of noninteracting fermions, we explore the full crossover from weak to strong dissipation regimes. The non-perturbative nature of the SGS ansatz allows us to thoroughly examine this crossover, providing comprehensive insights into the system's behavior. In the strong dissipation regime, our approach reproduces the finding that localized two-body losses can induce the Kondo effect [arXiv:2406.03527], characterized by a slowdown of spin relaxation and an enhancement of charge conductance. Furthermore, we reveal an exotic "reverse conductance" phenomenon at zero potential bias -- a counter-intuitive single-body effect resulting from intermediate dissipation and finite bandwidth. Finally, we investigate the formation of ferromagnetic domains and propose an extension to realize a higher-spin Kondo model using localized dissipation.
- [6] arXiv:2411.13642 [pdf, html, other]
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Title: Designing Atomtronic Circuits via Superfluid DynamicsComments: 9 pages, 8 figuresSubjects: Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)
We propose to design atomtronic circuits with Bose-Einstein condensates (BECs) in circuit-like traps that are controlled via mobile barriers. Using classical-field simulations, we demonstrate a universal set of logical gates and show how to assemble them into circuits. We first demonstrate an AND gate based on a T-shaped BEC, utilizing a combination of mobile and static barriers. The mobile barriers provide the logical input of the gate, while the static barrier functions as a Josephson junction that generates the AND output of the gate via a density imbalance across the barrier. Next we show how to combine three AND gates into a circuit, with a design composed of two T-shapes and an H-shape. Furthermore, we demonstrate how to use Josephson oscillations to create a NOT gate and combine it with an AND gate, thereby showcasing a universal set of gates and their assembly into circuits.
- [7] arXiv:2411.13644 [pdf, html, other]
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Title: Predicting interacting Green's functions with neural networksComments: 8 pages, 9 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el); Disordered Systems and Neural Networks (cond-mat.dis-nn)
Strongly correlated materials exhibit complex electronic phenomena that are challenging to capture with traditional theoretical methods, yet understanding these systems is crucial for discovering new quantum materials. Addressing the computational bottlenecks in studying such systems, we present a proof-of-concept machine learning-based approach to accelerate Dynamical Mean Field Theory (DMFT) calculations. Our method predicts interacting Green's functions on arbitrary two-dimensional lattices using a two-step ML framework. First, an autoencoder-based network learns and generates physically plausible band structures of materials, providing diverse training data. Next, a dense neural network predicts interacting Green's functions of these physically-possible band structures, expressed in the basis of Legendre polynomials. We demonstrate that this architecture can serve as a substitute for the computationally demanding quantum impurity solver in DMFT, significantly reducing computational cost while maintaining accuracy. This approach offers a scalable pathway to accelerate simulations of strongly correlated systems and lays the groundwork for future extensions to multi-band systems.
- [8] arXiv:2411.13647 [pdf, other]
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Title: CeCo$_2$P$_2$: a unique Co-antiferromagnetic topological heavy-fermion system with $P\cdot\mathcal{T}$-protected Kondo effect and nodal-line excitationsComments: 67 pages, 30 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el)
Based on high-throughput screening and experimental data, we find that CeCo$_2$P$_2$ is unique in heavy-fermion materials: it has a Kondo effect at a high temperature which is nonetheless below a Co-antiferromagnetic ordering temperature. This begs the question: how is the Kondo singlet formed? All other magnetic Kondo materials do not first form magnetism on the atoms whose electrons are supposed to screen the local moments. We theoretically explain these observations and show the multifaceted uniqueness of CeCo$_2$P$_2$: a playground for Kondo, magnetism, flat band, and topological physics. At high temperatures, the itinerant Co $c$ electrons of the system form non-atomic bands with a narrow bandwidth, leading to a high antiferromagnetic transition temperature. We show that the quantum geometry of the bands promotes in-plane ferromagnetism, while the weak dispersion along the $z$ direction facilitates out-of-plane antiferromagnetism. At low temperatures, we uncover a novel phase that manifests the coexistence of Co-antiferromagnetism and the Kondo effect, linked to the $P\cdot \mathcal{T}$-protected Kramers' doublets and the filling-enforced metallic nature of $c$ electrons in the antiferromagnetic phase. Subsequently, the emergence of the Kondo effect, in cooperation with glide-mirror-$z$ symmetry, creates nodal-line excitation near the Fermi energy. Our results emphasize the importance of lattice symmetry and quantum geometry, Kondo physics, and magnetism in the understanding of the correlation physics of this unique compound. We also test our theory on the structurally similar compound LaCo$_2$P$_2$ and show how we are able to understand its vastly different phase diagram.
- [9] arXiv:2411.13649 [pdf, html, other]
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Title: Edge thermal current of the topological insulatorComments: arXiv admin note: substantial text overlap with arXiv:2404.16937Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
We develop a systematic approach to calculate the contribution of edge states to the thermal Hall conductivity and energy magnetization. A two-dimensional topological insulator in equilibrium at a finite temperature is analyzed in the presence of a static gravitational field, which mimics the variations in the temperature distribution. From this model, an effective boundary free energy functional for the gravitational field is derived. Our analysis reveals that, unlike in the case of massive Dirac fermions, the addition of the Newtonian mass term in the topological insulator model significantly modifies the quantum anomalous behavior of the boundary states, leading to a non-zero bulk thermal current. This additional contribution violates the Wiedemann-Franz law.
- [10] arXiv:2411.13650 [pdf, html, other]
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Title: Theory of charge dynamics in bilayer electron system with long-range Coulomb interactionComments: 43 pages, 18 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con)
We perform a comprehensive study of charge excitations in a bilayer electron system in the presence of the long-range Coulomb interaction (LRC). Our major point is to derive formulae of the LRC that fully respect the bilayer lattice structure. This is an extension of the LRC obtained by Fetter in the electron-gas model 50 years ago and can now be applicable to any electron density. We then provide general formulae of the charge susceptibility in the random phase approximation and study them numerically. The charge ordering tendency is not found and instead we find two plasmon modes, w_{+} and w_{-} modes. Our second major point is to elucidate their spectral weight distribution and the effect of electron tunneling between the layers. The spectral weight of the w_{+-} modes does not have 2pi periodicity along the q_{z}c direction. The w_{+} mode loses spectral weight at inplane momentum q_{||}=(0,0) at q_{z}c=2n pi with n being integer whereas the w_{-} mode has no spectral weight at q_{z}c=0 for any q_{||} but acquires sizable spectral weight at q_{z}c=2n pi with n \ne 0. Both w_{+-} modes are gapped at q_{||}=(0,0). When q_{z}c is away from 2n pi, the w_{+-} modes show striking behavior. When the intrabilayer hopping t_z is relatively small (large), the w_{-} (w_{+}) mode becomes gapless at q_{||}=(0,0) whereas the w_{+} (w_{-}) mode retains the gap. However, when the interbilayer hopping integral t_{z}' is taken into account, the gapless mode acquires a gap at q_{||}=(0,0) and both w_{+-} modes are gapped at any q_{z}c. To highlight the special feature of the LRC, we also clarify a difference to the case of a short-range interaction. While the strong electron correlation effects are not included, the present theory captures available data of the charge excitations observed by resonant inelastic x-ray scattering for Y-based cuprate superconductors.
- [11] arXiv:2411.13651 [pdf, html, other]
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Title: Certain BCS wavefunctions are quantum many-body scarsSubjects: Strongly Correlated Electrons (cond-mat.str-el); Statistical Mechanics (cond-mat.stat-mech); Superconductivity (cond-mat.supr-con); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)
We provide a method for constructing many-body scar states in fermionic lattice models that incorporate a given type of correlations with one of the states maximizing them over the full Hilbert space. Therefore this state may always be made the ground state by adding such correlations as a "pairing potential" $\delta H_0$ to any Hamiltonian $H=H_0+OT$ supporting group-invariant scars [arXiv:2007.00845]. In case of single-flavour spin-full fermions the ground state is a special case of the BCS wavefunction written in real space and invariant under any site index relabelling. For multi-orbital fermions this state also resembles BCS but includes higher order terms corresponding to "pairing" of more than two fermions. The broad class of eligible Hamiltonians $H$ is well documented [arXiv:2007.00845],[arXiv:2106.10300] and includes many conventional condensed matter interactions. The part of the Hamiltonian $(H_0+\delta H_0)$ that governs the exact dynamics of the scar subspace coincides with the BCS mean-field Hamiltonian. We therefore show that its BCS ground state and the excitations above it are many-body scars that are dynamically decoupled from the rest of the Hilbert space and thereby protected from thermalization. These states are insensitive to a variety of $OT$ Hamiltonian terms that among others include interactions and (spin-orbit) hoppings. Our results point out a connection between the fields of superconductivity and weak ergodicity breaking (many-body scars) and will hopefully encourage further investigations. They also provide the first practical protocol to initialize a fermionic system to a scar state in (a quantum simulator) experiment.
- [12] arXiv:2411.13654 [pdf, html, other]
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Title: Friedel oscillations in one-dimensional 4HeComments: 5 pages, 4 figures + supplement. For associated data and code repository see: this https URLSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
One-dimensional bosonic systems, such as helium confined to nanopores, exhibit Luttinger liquid behavior characterized by density waves as collective excitations. We investigate the impact of a scattering potential on a low dimensional quantum liquid. We consider a microscopic model of $^4$He inside a perturbed nanopore with a localized constriction, and employ quantum Monte Carlo simulations to analyze the density of the core within an effective low-energy framework. Our results reveal the emergence of Friedel oscillations in a bosonic quantum liquid without a Fermi surface. Furthermore, we utilize the Luttinger liquid model to predict experimentally observable signatures of this pinning phenomena in elastic scattering and via the temperature and pressure dependence of mass transport through the deformed nanopore.
- [13] arXiv:2411.13658 [pdf, other]
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Title: Direct X-Ray Measurements of Strain in Monolayer MoS$_{2}$ from Capping Layers and Geometrical FeaturesKathryn Neilson, Marc Jaikissoon, Dante Zakhidov, Tara Peña, Alberto Salleo, Krishna Saraswat, Eric PopSubjects: Materials Science (cond-mat.mtrl-sci)
Strain induced through fabrication, both by patterning and capping, can be used to change the properties of two-dimensional (2D) materials or other thin films. Here, we explore how capping layers impart strain to monolayer MoS$_{2}$ using direct x-ray diffraction measurements of the lattice. We first observe the impact of naturally-oxidized metal layers ($\sim$1.5 nm Al) and subsequently-deposited Al$_{2}$O$_{3}$ (15 nm to 25 nm thick) on the 2D material, and find that the strain imparted to MoS$_{2}$ is mainly controlled by the interfacial adhesion of the seed layer in addition to the substrate adhesion. Then, using test structures which mimic transistor contacts, we measure enhanced strain from such patterns compared to blanket films. Furthermore, we observe significant tensile strain - up to 2% in monolayer MoS$_{2}$, one of the largest experimental values to date on a rigid substrate - due to highly-stressed blanket metal capping layers. These results provide direct evidence supporting previous reports of strain effects in 2D material devices.
- [14] arXiv:2411.13665 [pdf, other]
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Title: Atomistic investigation of irradiation-induced defect dynamics in FeNiCu medium-entropy alloy: effect of local chemical orderComments: 32 pages, 10 figuresSubjects: Materials Science (cond-mat.mtrl-sci)
Medium and high-entropy alloys (M/HEAs) have garnered significant attention as potential nuclear structural materials due to their excellent stability at high temperatures and resistance to radiation. However, the common use of Co in M/HEAs, which exhibits high radioactivity under radiation has prompted the development of Co-free M/HEAs for nuclear applications. In this study, we investigate the irradiation behavior of FeNiCu, a promising Co-free medium-entropy alloy (MEA) with a focus on the effect of local chemical order (LCO) using hybrid-molecular dynamics and Monte Carlo simulations. Considerable LCOs in Cu-Cu and Fe-Ni pairs were observed in the thermodynamically stable ordered system. To conduct a comprehensive comparative study of irradiation-induced defect formation and dynamics, cumulative displacement cascades up to 500 were performed in random and ordered configurations of the MEA as well as in pure Ni for benchmark. Our study revealed LCO configuration as the most radiation resistant structure among the three. Complex potential energy landscape (PEL) in MEAs disrupts dislocation growth resulting in its dispersed distribution. The Cu-rich uniform regions in the ordered system act as defect traps enabling faster diffusion and high defect recombination resulting in formation of the dislocation networks in/near these regions. The lower stair-rod dislocation density in the ordered system revealed its high resistance to irradiation swelling signifying the effect of LCO even more, positioning FeNiCu MEA as a strong candidate for future nuclear application. Additionally, the theoretical insights into defect evolution covering formation and diffusion in both random and ordered structures enhance our understanding of LCO's impact, offering a solid foundation for the future development of radiation-resistant M/HEAs for nuclear applications.
- [15] arXiv:2411.13670 [pdf, other]
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Title: Graph neural network framework for energy mapping of hybrid monte-carlo molecular dynamics simulations of Medium Entropy AlloysComments: 28 pages, 9 figuresSubjects: Materials Science (cond-mat.mtrl-sci); Machine Learning (cs.LG)
Machine learning (ML) methods have drawn significant interest in material design and discovery. Graph neural networks (GNNs), in particular, have demonstrated strong potential for predicting material properties. The present study proposes a graph-based representation for modeling medium-entropy alloys (MEAs). Hybrid Monte-Carlo molecular dynamics (MC/MD) simulations are employed to achieve thermally stable structures across various annealing temperatures in an MEA. These simulations generate dump files and potential energy labels, which are used to construct graph representations of the atomic configurations. Edges are created between each atom and its 12 nearest neighbors without incorporating explicit edge features. These graphs then serve as input for a Graph Convolutional Neural Network (GCNN) based ML model to predict the system's potential energy. The GCNN architecture effectively captures the local environment and chemical ordering within the MEA structure. The GCNN-based ML model demonstrates strong performance in predicting potential energy at different steps, showing satisfactory results on both the training data and unseen configurations. Our approach presents a graph-based modeling framework for MEAs and high-entropy alloys (HEAs), which effectively captures the local chemical order (LCO) within the alloy structure. This allows us to predict key material properties influenced by LCO in both MEAs and HEAs, providing deeper insights into how atomic-scale arrangements affect the properties of these alloys.
- [16] arXiv:2411.13689 [pdf, html, other]
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Title: Accelerating active learning materials discovery with FAIR data and workflows: a case study for alloy melting temperaturesSubjects: Materials Science (cond-mat.mtrl-sci)
Active learning (AL) is a powerful sequential optimization approach that has shown great promise in the discovery of new materials. However, a major challenge remains the acquisition of the initial data and the development of workflows to generate new data at each iteration. In this study, we demonstrate a significant speedup in an optimization task by reusing a published simulation workflow available for online simulations and its associated data repository, where the results of each workflow run are automatically stored. Both the workflow and its data follow FAIR (findable, accessible, interoperable, and reusable) principles using nanoHUB's infrastructure. The workflow employs molecular dynamics to calculate the melting temperature of multi-principal component alloys. We leveraged all prior data not only to develop an accurate machine learning model to start the sequential optimization but also to optimize the simulation parameters and accelerate convergence. Prior work showed that finding the alloy composition with the highest melting temperature required testing 15 alloy compositions, and establishing the melting temperature for each composition took, on average, 4 simulations. By developing a workflow that utilizes the FAIR data in the nanoHUB database, we reduced the number of simulations per composition to one and found the alloy with the lowest melting temperature testing only three compositions. This second optimization, therefore, shows a speedup of 10x as compared to models that do not access the FAIR databases.
- [17] arXiv:2411.13695 [pdf, other]
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Title: Robust coherent dynamics of homogeneously limited anisotropic excitons in two-dimensional layered ReS2Rup Kumar Chowdhury, Md Samiul Islam, Marie Barthelemy, Nicolas Beyer, Lorry Engel, Jean-Sebastien Pelle, Mircea Rastei, Alberto Barsella, Francois FrasSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics); Quantum Physics (quant-ph)
The discovery of in-plane anisotropic excitons in two-dimensional layered semiconductors enables state-of-the-art nanophotonic applications. A fundamental yet unknown parameter of these quasiparticles is the coherence time (T_2 ), which governs the quantum dephasing timescale, over which the coherent superposition of excitons can be maintained and manipulated. Here, we report the direct measurement of T_2 within the sub-picosecond range, along with multiple population decay timescales (T_1 ) at resonance for anisotropic excitons in pristine layered rhenium disulfide (ReS2). We observe a notable weak dependence on layer thickness for T_2 , and a quasi-independence for T_1 . The excitonic coherence in few-layer ReS2 exhibits exceptional robustness against optical density and temperature compared to other two-dimensional semiconductors, enabling quantum features even at room temperature. No photon echo fingerprints were observed in pristine ReS2, highlighting the homogeneous character of the anisotropic excitonic transitions and a particularly low level of disorder in exfoliated flakes. Lastly, our results for mono- to bulk-like ReS2 support a direct gap band structure regardless their layer thickness, addressing the ongoing discussion about its nature.
- [18] arXiv:2411.13705 [pdf, html, other]
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Title: A critical state under weak measurement is not criticalComments: 10 pages main text, 8 pages appendicesSubjects: Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics - Theory (hep-th)
Critical systems host nontrivial entanglement structure that is generally sensitive to additional couplings. In the present work, we study the effect of weak measurements on the entanglement Hamiltonian of massless free fermions which are prepared in their critical ground state. While the power-law decaying correlation and logarithmic growing entanglement entropy have been observed as typical signatures of quantum criticality after the weak measurement, in this work we show that the conformal symmetry is lost and the entanglement Hamiltonian generally becomes gapped for arbitrary small measurement strength. To reveal this unconventional entanglement structure, we consider a field-theory description that allows us to establish an analytic mapping between the entanglement Hamiltonians before and after the weak measurements. From this mapping, we find that although the measurements lead to a significant modification of the entanglement spectrum, the real-space distribution of the eigenfunction of the kernel of entanglement Hamiltonian is unchanged, which is responsible for the coexistence of a gapped entanglement Hamiltonian and the logarithmic entanglement entropy. Moreover, as the mapping works for arbitrarily many disjoint intervals, the multi-interval entanglement entropy also exhibits the same scaling behavior as the critical ground state, and shares the same effective central charge with the single-interval case. We numerically demonstrate these field-theory results on a lattice model, where the entanglement Hamiltonian after weak measurements exhibits the typical signature of a finite gap and becomes long-ranged even in the single-interval case. This is distinct from the critical ground state, where the entanglement Hamiltonian for a single interval is gapless and local.
- [19] arXiv:2411.13721 [pdf, html, other]
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Title: Enhanced Antiferromagnetic Phase in Metastable Self-Intercalated Cr$_{1+x}$Te$_2$ CompoundsClayton Conner, Ali Sarikhani, Theo Volz, Mitchel Vaninger, Xiaoqing He, Steven Kelley, Jacob Cook, Avinash Sah, John Clark, Hunter Lucker, Cheng Zhang, Paul Miceli, Yew San Hor, Xiaoqian Zhang, Guang BianComments: 5 figures, 1 tableSubjects: Materials Science (cond-mat.mtrl-sci)
Magnetic transition-metal dichalcogenides (TMDs) have been of particular interest due to their unique magnetic properties and layered structure that can be promising for a wide range of spintronic applications. One of the most exciting compounds in this family of magnets is chromium telluride, Cr$_{1+x}$Te$_2$, which has shown rich magnetic phases with varied Cr concentrations. An emergent antiferromagnetic (AFM) ordering has been found in Cr$_{1.25}$Te$_2$ (equivalently, Cr$_{5}$Te$_8$), which is induced by intercalating 0.25 Cr atom per unit cell within the van der Waals (vdW) gaps of CrTe$_2$. In this work, we report an increased Néel Temperature ($T_\mathrm{N}$) of the AFM phase in Cr$_{1+x}$Te$_2$ by slightly reducing the concentration of Cr intercalants. Moreover, the intercalated Cr atoms form a metastable 2$\times$2 supercell structure that can be manipulated by electron beam irradiation. This work offers a promising approach to tuning magnetic and structural properties by adjusting the concentration of self-intercalated magnetic atoms.
- [20] arXiv:2411.13727 [pdf, html, other]
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Title: Sign of the Gap Temperature Dependence in CsPb(Br,Cl)3 Nanocrystals Determined by Cs-Rattler Mediated Electron-Phonon CouplingS. Fasahat, N. Fiuza-Maneiro, B. Schäfer, K. Xu, S. Gómez-Graña, M. I. Alonso, L. Polavarapu, A. R. GoñiComments: 18 pages, 4 figures, 1 tableSubjects: Materials Science (cond-mat.mtrl-sci)
So far, the striking sign reversal in the near-ambient slope of the gap temperature dependence of colloidal CsPbCl3 perovskite nanocrystals (NCs) compared to its Br counterpart, remains unresolved. Pure bromide NCs exhibit a linear gap increase with increasing temperature, to which thermal expansion and electron-phonon interaction equally contribute. In contrast, the temperature slope for the chlorine compound gap is outspoken negative. By combining temperature and pressure-dependent photoluminescence on a series of CsPb(Br1-xClx)3 NCs, we unravel the origin of such inversion. Responsible is solely the electron-phonon interaction, undergoing a sudden change in sign and magnitude due to activation of an anomalous electron-phonon coupling mechanism linked to vibrational modes characterized by synchronous octahedral tilting and Cs rattling. This takes place in the shrunken orthorhombic NC lattice for Cl concentrations exceeding ca. 40%. We have thus clarified a puzzling result directly impacting the optoelectronic properties of lead halide perovskite NCs.
- [21] arXiv:2411.13743 [pdf, html, other]
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Title: The Gr\"uneisen parameter applied to critical phenomena and experimental investigations of correlated phenomena in molecular conductorsComments: Ph.D. Thesis, 135 pages, 40 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el); Other Condensed Matter (cond-mat.other); Statistical Mechanics (cond-mat.stat-mech)
In this Ph.D. Thesis, a systematic review is performed on the derivation and generalization of the Grüneisen parameter followed by its unprecedented applications to several distinct scenarios, such as magnetic model systems, zero-field quantum phase transitions, the maximization of caloric effects close to any critical-end point based on entropy arguments, the here-proposed adiabatic magnetization of a paramagnetic salt, as well as for Cosmology in the frame of the universe expansion. Since this Ph.D. Thesis is a symbiosis between theoretical and experimental results, an experimental investigation of correlated phenomena was carried out for molecular conductors of the (TMTTF)$_2$X family, where TMTTF is the base molecule tetramethyltetrathiafulvalene and X a monovalent counter-anion such as PF$_6$, SbF$_6$, or AsF$_6$. Such strongly correlated electron systems are considered suitable ones for the exploration of Mott insulating phase, charge-ordering, spin-Peierls, and superconductivity. In particular, the investigation of a possible multiferroic character in these salts was performed via quasi-static (low-frequency) dielectric constant $\varepsilon'$ measurements as a function of temperature where a maximum in $\varepsilon'$ as a function of temperature was observed at the corresponding charge-ordering temperature for both hydrogenated and 97.5% deuterated (TMTTF)$_2$SbF$_6$ salts. Furthermore, Raman measurements were performed on the 97.5% deuterated (TMTTF)$_2$PF$_6$, showing a possible magneto-optical effect on the $\nu_4(a_g)$ vibrational mode of the TMTTF molecule. Yet, fluorescence measurements demonstrated that the fully-hydrogenated (TMTTF)$_2$AsF$_6$ presents an expressive fluorescence background, which is roughly five orders of magnitude lower than that for the 97.5% deuterated variant of (TMTTF)$_2$PF$_6$.
- [22] arXiv:2411.13744 [pdf, html, other]
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Title: Xenon-metal pair formation in UO2 investigated using DFT+USubjects: Materials Science (cond-mat.mtrl-sci)
A recent experimental study on a spent uranium dioxide (UO2) fuel sample from Belgium Reactor3 (BR3) identified a unique pair structure formed by the noble metal phase (NMP) and fission gas (xenon [Xe]) precipitate. However, the fundamental mechanism behind this structure remains unclear. The present study aims to provide a comprehensive understanding of the interaction between five different metal precipitates (molybdenum [Mo], ruthenium [Ru], palladium [Pd], technetium [Tc], and rhodium [Rh]) and the Xe fission gas atoms in UO2, by using density functional theory (DFT) in combination with the Hubbard U correction to compute the formation energies involved. All DFT+U calculations were performed with occupation matrix control to ensure antiferromagnetic ordering of UO2. The calculated formation energies of the Xe and solid fission products in the NMP reveal that these metal precipitates form stable structures with Xe in the following order: Mo > Tc > Ru > Pd > Rh. Notably, the formation energy of Xe-metal pairs is lower than that of the isolated single defects in all instances, with Mo showing the most negative formation energy, likely accounting for the observed pair structure formation.
- [23] arXiv:2411.13745 [pdf, other]
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Title: Hot Carrier Dynamics in Operational Metal Halide Perovskite Solar CellsHadi Afshari, Varun Mapara, Shashi Sourabh, Megh N. Khanal, Vincent R. Whiteside, Rebecca A. Scheidt, Matthew C. Beard, Giles E. Eperon, Ian R. Sellers, Madalina FurisSubjects: Materials Science (cond-mat.mtrl-sci)
One of the main approaches to inhibit carrier cooling in semiconductor systems enabling the study of hot carrier solar cell protocols is the use of concentrated illumination to obtain high power densities and create a phonon bottleneck. This, however, typically also increases the lattice temperature of the solar cells significantly. Accordingly, the solar cells subject to high concentration illumination also need to withstand high operating temperatures. Having previously demonstrated the high temperature tolerance of the triple halide perovskite (FA0.8Cs0.2Pb1.02I2.4Br0.6Cl0.02) solar cells, here the hot carrier relaxation dynamics are studied in these devices using high power transient absorption (TA) measurements. In addition to monitoring TA spectra obtained at different time delays, the thermalization mechanisms of hot carriers is mapped with power dependent TA to extract the carrier cooling time in this system under in-operando conditions at various bias conditions that reflect the Jsc, Vmax and Voc of these structures, and subsequently deconvolve the underlying physics of carrier relaxation; as well as track the dynamics of the thermalization close to working conditions of the solar cells. These measurements uncover a complex interaction of hot carrier thermalization involving the temporal carrier density, transport, and extraction, and apparent non-equivalent contributions with respect to non-equilibrium photogenerated electrons and holes in these metal halide perovskite solar cell architectures.
- [24] arXiv:2411.13752 [pdf, html, other]
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Title: Coarse-Grained Simulation Model for Crystalline Polymer Solids by using Breakable BondsComments: 26 pages, 14 figures, to appear in J. Phys. Chem. BSubjects: Soft Condensed Matter (cond-mat.soft)
We propose a highly coarse-grained simulation model for crystalline polymer solids with crystalline lamellar structures. The mechanical properties of a crystalline polymer solid are mainly determined by the crystalline lamellar structures. This means that coarse-grained models rather than fine-scale molecular models are suitable to study mechanical properties. We model a crystalline polymer solid by using highly coarse-grained particles, of which size is comparable to the crystalline layer thickness. One coarse-grained particle consists of multiple subchains, and is much larger than monomers. Coarse-grained particles are connected by bonds to form a network structure. Particles are connected by soft but ductile bonds, to form a rubber-like network. Particles in the crystalline region are connected by hard but brittle bonds. Brittle bonds are broken when large deformations are applied. We perform uniaxial elongation simulations based on our coarse-grained model. As the applied strain increases, crystalline layers are broken into pieces and non-affine and collective motions of broken pieces are observed. Our model can successfully reproduce yield behaviors which are similar to typical crystalline polymer solids.
- [25] arXiv:2411.13795 [pdf, html, other]
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Title: Hidden altermagnetismComments: 7 pages, 5 figuresSubjects: Materials Science (cond-mat.mtrl-sci)
Hidden spin polarization (HSP) with zero net spin polarization in total but non-zero local spin polarization has been proposed in certain nonmagnetic centrosymmetric compounds, where the individual sectors forming the inversion partners are all inversion asymmetry. Here, we extend this idea to antiferromagnetic materials with $PT$ symmetry (the joint symmetry of space inversion symmetry ($P$) and time-reversal symmetry ($T$)), producing zero net spin polarization in total, but either of the two inversion-partner sectors possesses altermagnetism, giving rise to non-zero local spin polarization in the real space, dubbed "hidden altermagnetism". By first-principle calculations, we predict that $PT$-symmetric bilayer $\mathrm{Cr_2SO}$ can serve as a possible candidate showing altermagnetic HSP. By applying an external electric field to break the global $P$ symmetry, the hidden altermagnetism can be separated and observed experimentally. Our works extend the hidden physics, and will also advance the theoretical and experimental search for new type of spin-polarized materials.
- [26] arXiv:2411.13835 [pdf, other]
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Title: Effects of Photopatterning Conditions on Azimuthal Surface Anchoring StrengthNilanthi P. Haputhanthrige (1,2), Mojtaba Rajabi (1), Oleg D. Lavrentovich (1,2,3) ((1) Advanced Materials and Liquid Crystal Institute, Kent State University, Kent, OH 44242, USA, (2) Department of Physics, Kent State University, Kent, OH 44242, USA, (3) Materials Science Graduate Program, Kent State University, Kent, OH 44242, USA)Comments: 21 Pages, 7 FiguresSubjects: Soft Condensed Matter (cond-mat.soft)
Spatially-varying alignment of liquid crystals is essential for research and applications. One widely used method is based on the photopatterning of thin layers of azo-dye molecules, such as Brilliant Yellow (BY), that serve as an aligning substrate for a liquid crystal. In this study, we examine how photopatterning conditions, such as BY layer thickness (b), light intensity (I), irradiation dose, and age affect the alignment quality and the strength of the azimuthal surface anchoring. The azimuthal surface anchoring coefficient, W, is determined by analyzing the splitting of integer disclinations into half-integer disclinations at prepatterned substrates. The strongest anchoring is achieved for b in the range of 5 - 8 nm. W increases with the dose, and within the same dose, W increases with I. Aging of a non-irradiated BY coating above 15 days reduces W. Sealed photopatterned cells filled with a conventional nematic preserve their alignment quality for up to four weeks, after which time W decreases. This work suggests the optimization pathways for photoalignment of nematic liquid crystals.
- [27] arXiv:2411.13841 [pdf, other]
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Title: Switchable Non-Hermitian Skin Effect in Bogoliubov ModesSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Interacting or nonlinear lattices can host emergent particle-like modes, such as Bogoliubov quasiparticles, whose band topology and other properties are potentially highly tunable. Despite originating in the study of superconducting materials, Bogoliubov quasiparticles can also occur in synthetic metamaterials. Here, we implement a nonlinear driven-dissipative circuit whose fluctutations are Bogoliubov modes possessing nontrivial non-Hermitian band topology. We show experimentally that the system exhibits a switchable non-Hermitian skin effect (NHSE), which abruptly appears when the on-site driving voltage amplitude exceeds a threshold. In contrast to earlier realizations of the NHSE and related phenomena in circuit models, the switchable NHSE in our system occurs in Bogoliubov modes, which are strongly affected by how the system is driven. Moreover, unlike other experimental platforms hosting non-Hermitian Bogoliubov modes, our system does not contain unconventional asymmetric hopping nonlinearities, only a local Kerr-type nonlinearity.
- [28] arXiv:2411.13853 [pdf, other]
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Title: On the geometry of topological defects in glassesSubjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Materials Science (cond-mat.mtrl-sci); Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech)
Recent studies point out far-reaching connections between the topological characteristics of structural glasses and their material properties, paralleling results in quantum physics that highlight the relevance of the nature of the wavefunction. However, the structural arrangement of the topological defects in glasses has so far remained elusive. Here we investigate numerically the geometry and statistical properties of the topological defects related to the vibrational eigenmodes of a prototypical three-dimensional glass. We find that at low-frequencies these defects form scale-invariant, quasi-linear structures and dictate the plastic events morphology when the system is subjected to a quasi-static shear, i.e., the eigenmode geometry shapes plastic behavior in 3D glasses. Our results indicate the existence of a deep link between the topology of eigenmodes and plastic energy dissipation in disordered materials, thus generalizing the known connection identified in crystalline materials. This link is expected to have consequences also for the relaxation dynamics in the liquid state, thus opening the door for a novel approach to describe this dynamics.
- [29] arXiv:2411.13872 [pdf, other]
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Title: Modeling the variability of memristive devices with hexagonal boron nitride as dielectricJuan B. Roldan, David Maldonado, C. Aguilera-Pedregosa, F.J. Alonso, Yiping Xiao, Yaqing Shen, Wenwen Zheng, Yue Yuan, Mario LanzaJournal-ref: IEEE Transactions on Electron Devices, 2022Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Variability in memristive devices based on h-BN dielectrics is studied in depth. Different numerical techniques to extract the reset voltage are described and the corresponding cycle-to-cycle variability is characterized by means of the coefficient of variance. The charge-flux domain was employed to develop one of the extraction techniques, the calculation of the integrals of current and voltage to obtain the charge and flux allows to minimize the effects of electric noise and the inherent stochasticity of resistive switching on the measurement data. A model to reproduce charge versus flux curves has been successfully employed. The device variability is also described by means of the time series analysis to assess the memory effect along a resistive switching series. Finally, we analyzed I-V curves under ramped voltage stress utilizing a simulator based on circuit breakers, the formation and rupture of the percolation paths that constitute the conductive nanofilaments is studied to describe the set and reset processes behind the resistive switching operation.
- [30] arXiv:2411.13882 [pdf, html, other]
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Title: A 2x2 quantum dot array in silicon with fully tuneable pairwise interdot couplingWee Han Lim, Tuomo Tanttu, Tony Youn, Jonathan Yue Huang, Santiago Serrano, Alexandra Dickie, Steve Yianni, Fay E. Hudson, Christopher C. Escott, Chih Hwan Yang, Arne Laucht, Andre Saraiva, Kok Wai Chan, Jesús D. Cifuentes, Andrew S. DzurakComments: 9 pages, 5 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)
Recent advances in semiconductor spin qubits have achieved linear arrays exceeding ten qubits. Moving to two-dimensional (2D) qubit arrays is a critical next step to advance towards fault-tolerant implementations, but it poses substantial fabrication challenges, particularly because enabling control of nearest-neighbor entanglement requires the incorporation of interstitial exchange gates between quantum dots in the qubit architecture. In this work, we present a 2D array of silicon metal-oxide-semiconductor (MOS) quantum dots with tunable interdot coupling between all adjacent dots. The device is characterized at 4.2 K, where we demonstrate the formation and isolation of double-dot and triple-dot configurations. We show control of all nearest-neighbor tunnel couplings spanning up to 30 decades per volt through the interstitial exchange gates and use advanced modeling tools to estimate the exchange interactions that could be realized among qubits in this architecture. These results represent a significant step towards the development of 2D MOS quantum processors compatible with foundry manufacturing techniques.
- [31] arXiv:2411.13898 [pdf, other]
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Title: Discovery of an Antiferromagnetic Topological Nodal-line Kondo SemimetalD. F. Liu, Y. F. Xu, H. Y. Hu, J. Y. Liu, T. P. Ying, Y. Y. Lv, Y. Jiang, C. Chen, Y. H. Yang, D. Pei, D. Prabhakaran, M. H. Gao, J. J. Wang, Q. H. Zhang, F. Q. Meng, B. Thiagarajan, C. Polley, M. Hashimoto, D. H. Lu, N. B. M. Schröter, V. N. Strocov, A. Louat, C. Cacho, D. Biswas, T.-L. Lee, P. Steadman, P. Bencok, Y. B. Chen, L. Gu, T. Hesjeda, G. van der Laan, H. Hosono, L. X. Yang, Z. K. Liu, H. Q. Yuan, B. A. Bernevig, Y. L. ChenComments: 17pages,4 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
The symbiosis of strong interactions, flat bands, topology and symmetry has led to the discovery of exotic phases of matter, including fractional Chern insulators, correlated moiré topological superconductors, and Dirac and Weyl semimetals. Correlated metals, such as those present in Kondo lattices, rely on the screening of local moments by a sea of non-magnetic conduction electrons. Here, we report on a unique topological Kondo lattice compound, CeCo2P2, where the Kondo effect - whose existence under the magnetic Co phase is protected by PT symmetry - coexists with antiferromagnetic order emerging from the flat bands associated with the Co atoms. Remarkably, this is the only known Kondo lattice compound where magnetic order occurs in non-heavy electrons, and puzzlingly, at a temperature significantly higher than that of the Kondo effect. Furthermore, at low temperatures, the emergence of the Kondo effect, in conjunction with a glide-mirror-z symmetry, results in a nodal line protected by bulk topology near the Fermi energy. These unusual properties, arising from the interplay between itinerant and correlated electrons from different constituent elements, lead to novel quantum phases beyond the celebrated topological Kondo insulators and Weyl Kondo semimetals. CeCo2P2 thus provides an ideal platform for investigating narrow bands, topology, magnetism, and the Kondo effect in strongly correlated electron systems.
- [32] arXiv:2411.13933 [pdf, other]
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Title: Dynamics of electron-electron correlated to electron-phonon coupled phase progression in trilayer nickelate La4Ni3O10Subjects: Strongly Correlated Electrons (cond-mat.str-el)
Trilayer nickelates are a rich class of materials exhibiting diverse correlated phenomena, including superconductivity, density wave transitions, non-Fermi liquid behavior along with an unusual metal-to-metal transition around T* ~ 150 K. Understanding the electronic correlations, lattice and charge dynamics are crucial to unreveal the origin of superconductivity and other instabilities in nickelates. Our in-depth Raman measurements shows that trilayer nickelate, La4Ni3O10, shows transition from electron-phonon coupled phase to the electron-electron correlated one below charge density wave transition around T* with an estimated energy gap of ~ 18-20 meV. The transition around T* is also accompanied by the emergence of zone folded phonon modes reflecting the transition into the charge density wave phase. Phonon modes self-energy parameters show anomalous changes around T* attributed to the electron-electron correlations, and renormalization rate of the phonon modes is much slower in the charge-ordered phase compared to the phase above T*. The transition around T* are marked by the suppression of electron-phonon coupling parameter by ~ 70 %, a change of the quasiparticle dynamics from non-Fermi liquid to the Landau-Fermi liquid type behaviour estimated using the low frequency Raman response.
- [33] arXiv:2411.13938 [pdf, html, other]
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Title: Ground-state phase transitions in spin-1 Bose-Einstein condensates with spin-orbit couplingComments: to be published in Physical Review ASubjects: Quantum Gases (cond-mat.quant-gas); Pattern Formation and Solitons (nlin.PS)
We investigate phase transitions of the ground state (GS) of spin-1 Bose-Einstein condensates under the combined action of the spin-orbit coupling (SOC) and gradient magnetic field. Introducing appropariate raising and lowering operators, we exactly solve the linear system. Analyzing the obtained energy spectrum, we conclude that simultaneous variation of the magnetic-field gradient and SOC strength leads to the transition of excited states into the GS. As a result, any excited state can transition to the GS, at appropriate values of the system's parameters. The nonlinear system is solved numerically, showing that the GS phase transition, similar to the one in the linear system, still exists under the action of the repulsive nonlinearity. In the case of weak attraction, a mixed state appears near the GS transition point, while the GS transitions into an edge state under the action of strong attractive interaction.
- [34] arXiv:2411.13940 [pdf, html, other]
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Title: Preparation and observation of anomalous counterpropagating edge states in a periodically driven optical Raman latticeComments: 13 pages, 10 figuresSubjects: Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)
Motivated by the recent observation of real-space edge modes with ultracold atoms [Braun et al., Nat. Phys. 20, 1306 (2024)], we investigate the preparation and detection of anomalous counterpropagating edge states -- a defining feature of the anomalous Floquet valley-Hall (AFVH) phase -- in a two-dimensional periodically driven optical Raman lattice. Modeling the atomic cloud with a Gaussian wave packet state, we explore, both analytically and numerically, how the population of edge modes depends on the initial-state parameters. In particular, we reveal that, in addition to the internal spin state, the initial momenta parallel and perpendicular to the boundary play essential roles: they independently control the selective population of edge states across distinct momenta and within separate quasienergy gaps. Furthermore, we examine the wave-packet dynamics of counterpropagating edge states and demonstrate that their characteristic motion is robust against long-range disorder. These results establish a theoretical framework for future experimental explorations of the AFVH phase and topological phenomena associated with its unique edge modes.
- [35] arXiv:2411.13947 [pdf, other]
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Title: Circular photogalvanic effect in an inversion-symmetry-broken bilayer germanium nanosheetTaiki Nishijima (1), Ei Shigematsu (1), Ryo Ohshima (1), Keigo Matsushita (2), Akio Ohta (2,3), Masaaki Araidai (2), Junji Yuhara (2), Masashi Kurosawa (2), Masashi Shiraishi (1), Yuichiro Ando (1,4,5) ((1) Kyoto Univ., (2) Nagoya Unib., (3) Fukuoka Univ., (4) PRESTO-JST)Comments: 18pages, 4figuresSubjects: Materials Science (cond-mat.mtrl-sci)
Spin-to-charge conversion in monolayer and bilayer germanium(Ge) nanosheets was demonstrated via the circular photogalvanic effect (CPGE). The CPGE current generated in a spin-splitting state of the Ge nanosheet reached a maximum value when the thickness of the Ge nanosheet corresponded to bilayer germanene, indicating that the top layer of the bilayer Ge nanosheet mainly contributed to the spin-to-charge conversion. Because the hybridization of orbitals is suppressed by isolation from the bottom Al layer for the top Ge nanosheet, the observed spin-to-charge conversion has a possibility to be related to the intrinsic features of germanene with breaking of inversion symmetry.
- [36] arXiv:2411.13954 [pdf, html, other]
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Title: Light-induced renormalization of the band structure of chiral telluriumG. Gatti, N. Tancogne-Dejean, H. Hübener, U. De Giovannini, J. Dai, S. Polishchuk, Ph. Bugnon, F. Frassetto, L. Poletto, M. Chergui, M. Grioni, A. Rubio, M. Puppin, A. CrepaldiComments: 6 pages, 3 figuresSubjects: Materials Science (cond-mat.mtrl-sci); Strongly Correlated Electrons (cond-mat.str-el)
Chirality in tellurium derives from a Peierls distortion driven by strong electron-phonon coupling, making this material a unique candidate for observing a light-induced topological phase transition. By using time- and angle-resolved photoelectron spectroscopy (trARPES), we reveal that upon near-infrared photoexcitation the Peierls gap is modulated by displacively excited coherent phonons with $\mathrm{A_{1g}}$ symmetry as well as chiral-symmetry-breaking $\mathrm{E'_{LO}}$ modes. By comparison with state-of-the-art TDDFT+U calculations, we reveal the microscopic origin of the in-phase oscillations of band edges, due to phonon-induced modulation of the effective Hubbard $U$ term.
- [37] arXiv:2411.13956 [pdf, html, other]
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Title: Hybrid dielectrophoretic-optical trap for microparticles in aqueous suspensionCarlos D. Gonzalez-Gomez, Jose Garcia-Guirado, Romain Quidant, Felix Carrique, Emilio Ruiz-Reina, Raul A. Rica-AlarconSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Applied Physics (physics.app-ph)
We demonstrate that a set of microfabricated electrodes can be coupled to a commercial optical tweezers device, implementing a hybrid electro-optical trap with multiple functionalities to manipulate micro/nanoparticles in suspension. Our design allows us to simultaneously trap tens of particles in a single potential well generated in the low electric field region of the electrode arrangement, taking advantage of negative dielectrophoresis. Together with the optical tweezers, we show that the hybrid scheme allows enhanced manipulation capabilities, including controlled loading and accumulation in the dielectrophoretic trap from the optical tweezers, selectivity, and tracking of the individual trajectories of trapped particles.
- [38] arXiv:2411.13971 [pdf, html, other]
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Title: How do imperfections cause asymmetry in elastic snap-through?Subjects: Soft Condensed Matter (cond-mat.soft)
A symmetrically-buckled arch whose boundaries are clamped at an angle has two stable equilibria: an inverted and a natural state. When the distance between the clamps is increased (i.e. the confinement is decreased) the system snaps from the inverted to the natural state. Depending on the rate at which the confinement is decreased ('unloading'), the symmetry of the system during snap-through may change: slow unloading results in snap-through occurring asymmetrically, while fast unloading results in a symmetric snap-through. It has recently been shown [Wang et al., Phys. Rev. Lett. 132, 267201 (2024)] that the transient asymmetry at slow unloading rates is the result of the amplification of small asymmetric precursor oscillations (shape perturbations) introduced dynamically to the system, even when the system itself is perfectly symmetric. In reality, however, imperfections, such as small asymmetries in the boundary conditions, are present too. Using numerical simulations and a simple toy model, we discuss the relative importance of intrinsic imperfections and initial asymmetric shape perturbations in determining the transient asymmetry observed. We show that, for small initial perturbations, the magnitude of the asymmetry grows in proportion to the size of the intrinsic imperfection but that, when initial shape perturbations are large, intrinsic imperfections are unimportant - the asymmetry of the system is dominated by the transient amplification of the initial asymmetric shape perturbations. We also show that the dominant origin of asymmetry changes the way that asymmetry grows dynamically. Our results may guide engineering and design of snapping beams used to control insect-sized jumping robots.
- [39] arXiv:2411.13998 [pdf, html, other]
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Title: Multi-impurity method for the bond-weighted tensor renormalization groupComments: 9 pages, 10 figuresSubjects: Statistical Mechanics (cond-mat.stat-mech); High Energy Physics - Lattice (hep-lat)
We propose a multi-impurity method for the bond-weighted tensor renormalization group (BWTRG) to compute the higher-order moment of physical quantities in a two-dimensional system. The replacement of the bond weight with an impurity matrix in a bond-weighted triad tensor network represents a physical quantity such as the magnetization and the energy. We demonstrate that the accuracy of the proposed method is much higher than the conventional tensor renormalization group for the Ising model and the 5-state Potts model. Furthermore, we perform the finite-size scaling analysis and observe that the dimensionless quantity characterizing the structure of the fixed point tensor satisfies the same scaling relation in the critical region as the Binder parameter. The estimated critical temperature dependence on the bond dimension indicates that the exponent relating the correlation length to the bond dimension varies continuously with respect to the BWTRG hyperparameter. We find that BWTRG with the optimal hyperparameter is more efficient in terms of computational time than alternative approaches based on the matrix product state in estimating the critical temperature.
- [40] arXiv:2411.14004 [pdf, html, other]
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Title: Evaluation of the probability current in the stochastic path integral formalismComments: 17 pagesSubjects: Statistical Mechanics (cond-mat.stat-mech)
The probability current is a vital quantity in the Fokker-Planck description of stochastic processes. It characterizes nonequilibrium stationary states, appears in linear response calculation, and has been related to the entropy production and the heat flux. We recover and review the probability current in the Onsager-Machlup functional approach to Markov processes. We derive a self contained expression for the stationary probability current and the non-equilibrium fluctuation-dissipation theorem using field theoretical methods. The derived formulas are explicitly evaluated in the Ornstein-Uhlenbeck process of a harmonically bound particle in shear flow as exemplary analytic expressions. Our work closes a gap since it removes a missing link, i.e.~the probability current, in the supposed equivalence of the Fokker-Planck and the path-integral approach.
- [41] arXiv:2411.14011 [pdf, html, other]
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Title: THz optical response of Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ films analyzed within the three-band Eliashberg s$_\pm $-wave modelYurii A. Aleshchenko (1), Andrey V. Muratov (1), Elena S. Zhukova (2), Lenar S. Kadyrov (2), Boris P. Gorshunov (2), Giovanni A. Ummarino (3 and 4), Ilya A. Shipulin (1) ((1) P.N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow, Russia, (2) Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia, (3) Istituto di Ingegneria e Fisica dei Materiali, Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, Torino, Italy, (4) National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia)Comments: 26 pages, 9 figures, 2 tables. arXiv admin note: text overlap with arXiv:2006.00522Journal-ref: Journal of Physics and Chemistry of Solids 196 (2025) 112364Subjects: Superconductivity (cond-mat.supr-con)
The uncertainty of the nature of the normal state and superconducting condensate of unconventional superconductors continues to stimulate considerable speculation about the mechanism of superconductivity in these materials. Of particular interest are the type of symmetry of the order parameter and the basic electronic characteristics of the superconducting and normal states. We report the derivation of temperature dependences of the superconducting condensate plasma frequency, superfluid density, and London penetration depth by measuring terahertz spectra of conductivity and dielectric permittivity of the Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ thin films with different Ni concentrations. A comprehensive analysis of the experimental data was performed in the framework of the simple three-band Eliashberg model under the assumption that the superconducting coupling mechanism is mediated by antiferromagnetic spin fluctuations. The results of independent experiments support the choice of model parameters. Based on calculations of the temperature dependences of superconducting gaps, we may conclude that the obtained results are compatible with the scenario, in which Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ is a multiband superconductor with s$_\pm $-wave pairing symmetry.
- [42] arXiv:2411.14034 [pdf, html, other]
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Title: Assessing data-driven predictions of band gap and electrical conductivity for transparent conducting materialsFederico Ottomano, John Y. Goulermas, Vladimir Gusev, Rahul Savani, Michael W. Gaultois, Troy D. Manning, Hai Lin, Teresa P. Manzanera, Emmeline G. Poole, Matthew S. Dyer, John B. Claridge, Jon Alaria, Luke M. Daniels, Su Varma, David Rimmer, Kevin Sanderson, Matthew J. RosseinskySubjects: Materials Science (cond-mat.mtrl-sci); Artificial Intelligence (cs.AI)
Machine Learning (ML) has offered innovative perspectives for accelerating the discovery of new functional materials, leveraging the increasing availability of material databases. Despite the promising advances, data-driven methods face constraints imposed by the quantity and quality of available data. Moreover, ML is often employed in tandem with simulated datasets originating from density functional theory (DFT), and assessed through in-sample evaluation schemes. This scenario raises questions about the practical utility of ML in uncovering new and significant material classes for industrial applications. Here, we propose a data-driven framework aimed at accelerating the discovery of new transparent conducting materials (TCMs), an important category of semiconductors with a wide range of applications. To mitigate the shortage of available data, we create and validate unique experimental databases, comprising several examples of existing TCMs. We assess state-of-the-art (SOTA) ML models for property prediction from the stoichiometry alone. We propose a bespoke evaluation scheme to provide empirical evidence on the ability of ML to uncover new, previously unseen materials of interest. We test our approach on a list of 55 compositions containing typical elements of known TCMs. Although our study indicates that ML tends to identify new TCMs compositionally similar to those in the training data, we empirically demonstrate that it can highlight material candidates that may have been previously overlooked, offering a systematic approach to identify materials that are likely to display TCMs characteristics.
- [43] arXiv:2411.14045 [pdf, html, other]
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Title: Suppression of Intrinsic Hall Effect through Competing Berry Curvature in Cr$_{1+\delta}$Te$_2$Prasanta Chowdhury, Jyotirmay Sau, Mohamad Numan, Jhuma Sannigrahi, Matthias Gutmann, Saurav Giri, Manoranjan Kumar, Subham MajumdarComments: 11 pages, 7 figuresSubjects: Materials Science (cond-mat.mtrl-sci)
We conducted a comprehensive analysis of the magnetic and electronic transport properties of the layered chalcogenide Cr$_{1+\delta}$Te$_2$ in its single crystalline form. This material exhibits a ferromagnetic transition at a critical temperature of $T_C = 191$ K, characterized by significant thermal hysteresis in the magnetization data below this temperature. Measurements of isothermal magnetization, magnetocaloric effect, and magnetoresistance indicate that the system exhibits strong magnetocrystalline anisotropy, with the $c$-axis serving as the easy axis of magnetization. The Cr$_{1+\delta}$Te$_2$ compound shows pronounced anomalous Hall effect (AHE); however, existing experimental and theoretical data do not provide a clear understanding of the nature and origin of this phenomenon. Our experimental findings suggest that the skew scattering mechanism primarily accounts for the observed AHE. In contrast, our theoretical study reveals the presence of gapped nodal points accompanied by non-zero Berry Curvature, which are expected to contribute towards intrinsic AHE. A detailed analysis of the electronic band structure, obtained through density functional theory calculations, reveals that the Berry Curvature at different nodal points exhibit both positive and negative signs. These opposing contributions largely cancel each other out, thereby significantly diminishing the intrinsic contribution to the AHE.
- [44] arXiv:2411.14061 [pdf, other]
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Title: One-step Synthesis of Cubic Gauche Polymeric Nitrogen with High Yield Just by HeatingComments: 7 pages, 4 figuresSubjects: Materials Science (cond-mat.mtrl-sci); Chemical Physics (physics.chem-ph)
A high-efficient one-step synthesis of cubic gauche polymeric nitrogen was developed just by thermal treatment of KN3 powders. The Raman and infrared spectra confirm the formation of polymeric nitrogen networks. Thermogravimetric differential scanning calorimeter measurements show that the content of cubic gauche polymeric nitrogen is as high as 1.5 wt% with high thermal stability, which is the highest content value so far.
- [45] arXiv:2411.14075 [pdf, html, other]
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Title: Photon drag at the junction between metal and 2d semiconductorSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)
Photon drag represents a mechanism of photocurrent generation wherein the electromagnetic (EM) field momentum is transferred directly to the charge carriers. It is believed to be small by the virtue of low photon momentum compared to the typical momenta of the charge carriers. Here, we show that photon drag becomes particularly strong at the junctions between metals and 2d materials, wherein highly non-uniform local EM fields are generated upon diffraction. To this end, we combine an exact theory of diffraction at 'metal-2d material' junctions with microscopic transport theory of photon drag, and derive the functional dependences of the respective photovoltage on the parameters of EM field and 2d system. The voltage responsivity appears inversely proportional to the electromagnetic frequency $\omega$, the sheet density of charge, and a dimensionless momentum transfer coefficient $\alpha$ which depends only on 2d conductivity in units of light speed $\eta = 2\pi \sigma/c$ and light polarization. For $p$-polarized incident light, the momentum transfer coefficient appears finite even for vanishingly small 2d conductivity $\eta$, which is a consequence of dynamic lightning rod effect. For $s$-polarized incident light, the momentum transfer coefficient scales as $\eta \ln \eta^{-1}$, which stems from long-range dipole radiation of a linear junction. A simple estimate shows that the ratio of thermoelectric and photon drag photovoltages at the junction for $p$-polarization is roughly $\omega\tau_\varepsilon$, where $\tau_\varepsilon$ is the energy relaxation time, while for $s$-polarization the photon drag always dominates over the thermoelectric effect.
- [46] arXiv:2411.14113 [pdf, other]
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Title: Promoting and imaging intervalley coherent order in rhombohedral tetralayer graphene on MoS2Wei-Yu Liao, Wen-Xiao Wang, Shihao Zhang, Yang Zhang, Ling-Hui Tong, Wenjia Zhang, Hao Cai, Yuan Tian, Yuanyuan Hu, Li Zhang, Lijie Zhang, Zhihui Qin, Long-Jing YinComments: 21 pages, 5 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Strongly Correlated Electrons (cond-mat.str-el)
Multilayer rhombohedral graphene (RG) has recently emerged as a new, structurally simple flat-band system, which facilitates the exploration of interaction-driven correlation states with highly ordered electron arrangements. Despite a variety of many-body order behaviors observed in RG by transport measurements, the direct microscopic visualization of such correlated phases in real space is still lacking. Here, we show the discovery of a robust intervalley coherent order, a long-predicted ground state in RG, at 77 K in tetralayer RG placed on MoS2 via imaging atomic-scale spatial reconstruction of wave functions for correlated states. By using scanning tunnelling microscopy, we observe spectroscopic signatures of electronic correlations at partially filled flat bands, where distinct splitting appears. At ~60% and ~70% fillings of the flat bands, we visualize atomic-scale reconstruction patterns with a <sqrt>3 x <sqrt>3 supercell on graphene lattice at liquid nitrogen temperature, which indicates a robust intervalley coherent phase of the interacting electrons. The <sqrt>3 x <sqrt>3 pattern is observed in MoS2-supported RG, while it is absent in hBN-based ones under the same experimental conditions, suggesting the significant influence of spin-orbit proximity effect. Our results provide microscopic insights into the correlated phases in tetralayer RG and highlight the significant potential for realizing highly accessible collective phenomena through Van der Waals proximity.
- [47] arXiv:2411.14114 [pdf, html, other]
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Title: Dirac and chiral spin liquids on spin-1/2 square-lattice Heisenberg antiferromagnetComments: 4 pages + 2 figures + supplementary materials. Comments are welcomeSubjects: Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con)
We revisit the challenging problem of identifying the quantum spin liquid candidate in the spin-1/2 $J_1$-$J_2$ Heisenberg antiferromagnet on the square lattice. By integrating the Gutzwiller-guided density matrix renormalization group method with analytical analyses, we present clear evidence that the ground state is a Z$_2$ Dirac spin liquid. This state can be efficiently described by a Gutzwiller-projected parton theory characterized by its projective symmetry group. To distinguish the difference between the projected Z$_2$ and U(1) parton state, we investigate the chiral spin liquid ground states as topological orders by incorporating a $J_\chi$ term into the $J_1$-$J_2$ model and observe a transition from a Z$_2$ chiral spin liquid to a U(1)$_2$ chiral spin liquid as $J_\chi$ increases.
- [48] arXiv:2411.14115 [pdf, other]
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Title: Systematic Fluorination is a Powerful Design Strategy Towards Fluid Molecular FerroelectricsSubjects: Soft Condensed Matter (cond-mat.soft)
Ferroelectric nematic (NF) liquid crystals combine liquid-like fluidity and orientational order of conventional nematics with macroscopic electric polarization comparable in magnitude to solid state ferroelectric materials. Here, we present a systematic study of twenty-seven homologous materials with various fluorination patterns, giving new insight into the molecular origins of spontaneous polar ordering in fluid ferroelectric nematics. Beyond our initial expectations, we find the highest stability of the NF phase to be in materials with specific fluorination patterns rather than the maximal fluorination which might be expected based on simple models. We find a delicate balance between polar and apolar nematics which is entirely dictated by the substitution of the fluorine atoms. Aided by electronic structure calculations, we show this to have its origins in the radial distribution of charge across the molecular surface, with molecules possessing a more oscillatory distribution of electrons across their surfaces possessing a higher propensity to form polar nematic phases. This work provides a new set of ground rules and designing principles which can inform the synthesis of future ferroelectric nematogens.
- [49] arXiv:2411.14118 [pdf, other]
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Title: Ferroelectric Nanoparticles in Liquid Crystals: The Role of Ionic Transport at Small Concentrations of the NanoparticlesJuliya M. Gudenko, Oleksandr S. Pylypchuk, Victor V. Vainberg, Igor A. Gvozdovskyy, Serhii E. Ivanchenko, Denis O. Stetsenko, Nicholas V. Morozovsky, Volodymir N. Poroshin, Eugene A. Eliseev, Anna N. MorozovskaComments: 16 pages, 7 figures, to be published in Semiconductor Physics, Quantum Electronics and Optoelectronics, vol. 28, No 1 (2025)Subjects: Materials Science (cond-mat.mtrl-sci); Soft Condensed Matter (cond-mat.soft)
We reveal the visible influence of the ultra-small concentrations (1 wt.% or less) of the BaTiO3 nanoparticles (average size 24 nm) on the current-voltage characteristics and capacitance of the dielectric liquid crystal (LC) 5CB. The pure LC cell demonstrates higher current (and thus smaller resistance) than the LC cells filled with a very small concentration (0.5-1) wt.% of BTO nanoparticles. The same trend is observed for the charge-voltage characteristics: the capacitance loop is the widest for the pure LC cell and becomes noticeably thinner in the presence of (0.5-1) wt.% of BaTiO3 nanoparticles. This seems counterintuitive, because 1 wt.% of ferroelectric nanoparticles very slightly modify the effective dielectric response and should not influence on the director distribution and elastic properties of the LC. We conclude that a possible physical reason of this observation is the influence of the ionic-electronic screening charges, which cover the ferroelectric nanoparticles and become polarized in the external field, on the ionic transport in the LC.
- [50] arXiv:2411.14136 [pdf, other]
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Title: Deformation and adiabatic heating of single crystalline and nanocrystalline Ni micropillars at high strain ratesComments: 11 pages (17 in total including supplementary information). 4 main figures, 4 supplementary figuresSubjects: Materials Science (cond-mat.mtrl-sci)
The deformation behavior of single crystal and nanocrystalline nickel were studied with in situ micropillar compression experiments from quasi-static to high strain rates up to 10^3/s. Deformation occurred by dislocation slip activity in single crystal nickel whereas extensive grain boundary sliding was observed in nanocrystalline nickel, with a shift towards more inhomogeneous, localized deformation above 1/s. The overall strain rate sensitivity was observed to be nearly two times in nanocrystalline nickel compared to single crystal, as expected. Crystal plasticity based finite element modeling was used to estimate the adiabatic heating, spatially resolved within pillar, at the highest tested strain rates. The simulations predicted a significant temperature rise up to ~ 200 K in nanocrystalline Ni at the grain boundaries and ~ 20 K in single crystalline Ni, due to strain localization. The strain rate sensitivity exponent was observed to remain roughly constant over the tested strain rate range suggesting no change in deformation mechanisms.
- [51] arXiv:2411.14140 [pdf, other]
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Title: Angular dependence of large negative magnetoresistance in a field-induced Weyl semimetal candidate HoAuSnYue Lu, Jie Chen, Feng Zhou, Yong-Chang Lau, Piotr Wisniewski, Dariusz Kaczorowski, Xue-Kui Xi, Wen-Hong WangSubjects: Materials Science (cond-mat.mtrl-sci)
The angular dependence of magnetoresistance (MR) in antiferromagnetic half-Heusler HoAuSn single crystals have been systematically studied. Negative MR, as large as 99%, is observed at 9 T, is not restricted to the specific configuration of applied magnetics fields and current, and can persist up to 20 K, much higher than the Neel temperature (TN 1.9 K). Experiments and first-principles calculations suggest that the observed large negative MR is derived from a magnetic field that reconstructs the band structure and induces a Weyl point, which changes the carrier concentration. Taking into consideration that large negative MR has so far been rarely reported, especially in antiferromagnetic materials, it is anticipated that the present work not only offers a guideline for searching materials with large negative MR but also helps to further realize other exotic topological electronic states in a large class of antiferromagnetic half-Heusler compounds.
- [52] arXiv:2411.14144 [pdf, html, other]
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Title: Superconducting $p$-wave pairing effects on one-dimensional non-Hermitian quasicrystals with power law hoppingComments: 11 pages, 6 figuresSubjects: Superconductivity (cond-mat.supr-con); Disordered Systems and Neural Networks (cond-mat.dis-nn); Other Condensed Matter (cond-mat.other); Quantum Physics (quant-ph)
We study the effects of superconducting $p$-wave pairing on the non-Hermitian Aubry-André-Harper model with power-law hopping. For the case of short-range hopping, weak pairing leads to oscillating quasi-Majorana zero modes, turning to edge-localized Majorana zero modes as pairing strength increases. For the case of long-range hopping, we observe the emergence of massive Dirac modes having oscillatory behavior, similar to Majorana modes with weak pairing. The massive Dirac modes localize at the edges as the pairing strength grows. The superconducting pairing spoils the plateaus observed in the fractal dimension of all the energy eigenstates of the Aubry-André-Harper model with power-law hopping. The number of plateaus decreases with the increasing pairing strength for the weak non-Hermiticity in the system. The phase diagram of the system reveals that real and complex energy spectrums correlate differently with the localization properties of the eigenstates depending on the strength of pairing and hopping range.
- [53] arXiv:2411.14152 [pdf, html, other]
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Title: Current-induced brightening of vacancy-related emitters in hexagonal boron nitrideCorinne Steiner, Rebecca Rahmel, Frank Volmer, Rika Windisch, Lars H. Janssen, Patricia Pesch, Kenji Watanabe, Takashi Taniguchi, Florian Libisch, Bernd Beschoten, Christoph Stampfer, Annika KurzmannComments: 16 pages, 8 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
We perform photoluminescence measurements on vacancy-related emitters in hexagonal boron nitride (hBN) that are notorious for their low quantum yields. The gating of these emitters via few-layer graphene electrodes reveals a reproducible, gate-dependent brightening of the emitter, which coincides with a change in the direction of the simultaneously measured leakage current across the hBN layers. At the same time, we observe that the relative increase of the brightening effect scales linearly with the intensity of the excitation laser. Both observations can be explained in terms of a photo-assisted electroluminescence effect. Interestingly, emitters can also show the opposite behavior, i.e. a decrease in emitter intensity that depends on the gate leakage current. We explain these two opposing behaviors with different concentrations of donor and acceptor states in the hBN and show that precise control of the doping of hBN is necessary to gain control over the brightness of vacancy-related emitters by electrical means. Our findings contribute to a deeper understanding of vacancy-related defects in hBN that is necessary to make use of their potential for quantum information processing.
- [54] arXiv:2411.14167 [pdf, html, other]
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Title: Quantitative modeling of spintronic terahertz emission due to ultrafast spin transportSubjects: Materials Science (cond-mat.mtrl-sci)
In spintronic terahertz emitters, THz radiation is generated by exciting an ultrafast spin current through femtosecond laser excitation of a ferromagnetic-nonmagnetic metallic heterostructure. Although an extensive phenomenological knowledge has been built up during the last decade, a solid theoretical modeling that connects the generated THz signal to the laser induced-spin current is still incomplete. Here, starting from general solutions to Maxwell's equations, we model the electric field generated by a superdiffusive spin current in spintronic emitters, taking Co/Pt as a typical example. We explicitly include the detector shape which is shown to significantly influence the detected THz radiation. Additionally, the electron energy dependence of the spin Hall effect is taken into account, as well as the duration of the exciting laser pulse and thickness of the detector crystal. Our modeling leads to realistic emission profiles and highlights the role of the detection method for distinguishing key features of the spintronic THz emission.
- [55] arXiv:2411.14197 [pdf, html, other]
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Title: Anomalous Transition in Thermal Conductivity in Germanene MonolayerComments: 7 pages, 6 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
We report an anomalous temperature-induced transition in thermal conductivity in germanene monolayer around a critical temperature $T_c = 350 \, \text{K}$. Equilibrium molecular dynamics simulations reveal a transition from $\kappa \sim T^{-2}$ scaling below $T_c$ to $\kappa \sim T^{-1/2}$ above, contrasting with conventional $\kappa \sim T^{-1}$ behavior. This anomalous scaling correlates with long-scale characteristics timescale $\tau_2$ obtained from double exponential fitting of heat current autocorrelation function. Phonon mode analysis using normal mode decomposition indicates that a redshift in TA phonons reduces the acoustic-optical phonon gap, enhancing the phonon-phonon scattering and driving the anomalous scaling behavior. Moreover, non equilibrium simulations find a convergent thermal conductivity of germanene with sample size, in agreement with mode coupling theory, owing to high scattering of ZA phonons due to the inherent buckling of germanene.
- [56] arXiv:2411.14212 [pdf, html, other]
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Title: Bound electron states in a charged chain within the Dirac descriptionComments: 12 pagesSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
For the first time the exact analytical expressions for the three-dimensional bound electron states in the Coulomb field of the chain consisting of positively charged ions, are obtained within the Dirac description, using the new spinor invariant found for this problem. It is demonstrated that within such approach the coupling between electron spin and its one-dimensional propagation along the chain naturally arise, without any need to include artificially into the equations the so-called spin-orbit interaction.
- [57] arXiv:2411.14216 [pdf, html, other]
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Title: Ferroelectric switchable altermagnetismMingqiang Gu, Yuntian Liu, Haiyuan Zhu, Kunihiro Yananose, Xiaobing Chen, Yongkang Hu, Alessandro Stroppa, Qihang LiuComments: 6 pages, 4 figuresSubjects: Materials Science (cond-mat.mtrl-sci)
We propose a novel ferroelectric switchable altermagnetism effect, the reversal of ferroelectric polarization is coupled to the switching of altermagnetic spin splitting. We demonstrate the design principles for the ferroelectric altermagnets and the additional symmetry constraints necessary for switching the altermagnetic spin splitting through flipping the electric polarization based on the state-of-the-art spin-group symmetry techniques. 22 ferroelectric altermagnets are found by screening through the 2001 experimental reported magnetic structures in the MAGNDATA database and 2 of them are identified as ferroelectric switchable altermagnets. Using the hybrid improper ferroelectric material [C(NH2)3]Cr(HCOO)3 as an example, we show how the altermagnetic spin splitting is tightly coupled to the ferroelectric polarization, providing an ideal platform for designing electric-field-controllable multiferroic devices. Finally, we find that such manipulation of altermagnetism can be detected by monitoring the physical quantities that are related to the non-vanishing Berry curvature dipole, such as the linearly polarized photogalvanic spin current.
- [58] arXiv:2411.14220 [pdf, other]
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Title: Self-passivation Causes the Different Fermi Level Pinning between Metal-Si and Metal-Ge ContactsComments: 20 pages, 10 figuresSubjects: Materials Science (cond-mat.mtrl-sci); Computational Physics (physics.comp-ph)
Metal-Ge contacts possess much stronger Fermi level pinning (FLP) than metal-Si contacts, which is commonly believed to be due to Ge having a narrower bandgap and higher permittivity in the context of FLP caused by metal-induced gap states. Here, we show that both Ge and Si have a similar FLP strength if they adopt an identical interface chemical bonding configuration at the contact interface by performing first-principles calculations: Si and Ge have FLP factors of 0.16 and 0.11, respectively, if they adopt the same reconstructed bonding configuration and have FLP factors of 0.05 and 0, respectively, if they adopt the same non-reconstructed bonding configuration. We illustrate that Ge prefers the latter configuration at the contact interface, which has denser dangling-bond-induced surface states, and Si prefers the latter one, which has a self-passivation effect for reducing the dangling bond-induced interface states, to reproduce the experimental data. By revealing the significance of dangling bond-induced interface gap states on FLP, these findings shed new light on lowering the contact resistance for developing future Si CMOS technology.
- [59] arXiv:2411.14229 [pdf, other]
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Title: Thermal emission of hydrogenated amorphous silicon microspheres in the mid-infraredComments: 9 pages, 6 figuresSubjects: Materials Science (cond-mat.mtrl-sci); Optics (physics.optics)
Hydrogenated amorphous silicon microspheres feature a pronounced phononic peak around 2000 cm-1 when they are thermally excited by means of a blue laser. This phononic signature corresponds to vibrational modes of silicon-hydrogen bonds and its emitted light can be coupled to Mie modes defined by the spherical cavity. The signal is apparently quite stable at moderate excitation intensities although there appeared some signs pointing to hydrides bonds reconfiguration and even hydrogen emission. Above a certain excitation threshold, a phase change from amorphous to poly-crystalline silicon occurs that preserves the good structural quality of the microspheres.
- [60] arXiv:2411.14244 [pdf, other]
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Title: Emergence of a Bandgap in Nano-Scale Graphite: A Computational and Experimental StudySujinda Chaiyachad, Trung-Phuc Vo, Sirisak Singsen, Tanachat Eknapakul, Warakorn Jindata, Chutchawan Jaisuk, Patrick Le Fevre, Francois Bertran, Donghui Lu, Yaobo Huang, Hideki Nakajima, Watchara Liewrian, Ittipon Fongkaew, Jan Minar, Worawat MeevasanaComments: 33 pages, 9 figuresSubjects: Materials Science (cond-mat.mtrl-sci)
Graphite, conventionally regarded as a gapless material, exhibits a bandgap of ~100 meV in nano-scale patterned highly oriented pyrolytic graphite (HOPG), as revealed by angle-resolved photoemission spectroscopy (ARPES). Our advanced first-principles calculations, incorporating photoemission matrix element effects, predict this bandgap with remarkable accuracy and attribute it to mechanical distortions introduced during patterning. This work bridges theory and experiment, providing the direct evidence of a tunable bandgap in HOPG. Beyond its fundamental significance, this finding opens new possibilities for designing materials with tailored electronic properties, enabling advancements in terahertz devices and optoelectronics.
- [61] arXiv:2411.14289 [pdf, html, other]
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Title: Octahedral tilt-driven phase transitions in BaZrS3 chalcogenide perovskiteSubjects: Materials Science (cond-mat.mtrl-sci); Chemical Physics (physics.chem-ph)
Chalcogenide perovskites are lead-free materials for potential photovoltaic or thermoelectric applications. BaZrS$_3$ is the most studied member of this family due to its superior thermal and chemical stability, desirable optoelectronic properties, and low thermal conductivity. Phase transitions of the BaZrS$_3$ perovskite are under-explored in literature as most experimental characterization is performed at ambient conditions where the orthorhombic Pnma phase is reported to be stable. In this work, we study the dynamics of BaZrS$_3$ across a range of temperatures and pressures using an accurate machine-learned interatomic potential trained with data from hybrid density functional theory calculations. At 0Pa, we find a first-order phase transition from the orthorhombic to tetragonal I4/mcm phase at 610K, and a second-order transition from the tetragonal to the cubic Pm-3m phase at 880K. The tetragonal phase is stable over a larger temperature range at higher pressures. To confirm the validity of our model we report the static structure factor as a function of temperature and compare our results with published experimental data.
- [62] arXiv:2411.14302 [pdf, html, other]
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Title: Electrodynamics of Vortices in Quasi-2D Scalar Bose-Einstein CondensatesComments: 15 pages, 1 figureSubjects: Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph); Plasma Physics (physics.plasm-ph); Quantum Physics (quant-ph)
In two spatial dimensions, vortex-vortex interactions approximately vary with the logarithm of the inter-vortex distance, making it possible to describe an ensemble of vortices as a Coulomb gas. We introduce a duality between vortices in a quasi-two-dimensional (quasi-2D) scalar Bose-Einstein condensates (BEC) and effective Maxwell's electrodynamics. Specifically, we address the general scenario of inhomogeneous, time-dependent BEC number density with dissipation or rotation. Starting from the Gross-Pitaevskii equation (GPE), which describes the mean-field dynamics of a quasi-2D scalar BEC without dissipation, we show how to map vortices in a quasi-2D scalar BEC to 2D electrodynamics beyond the point-vortex approximation, even when dissipation is present or in a rotating system. The physical meaning of this duality is discussed.
- [63] arXiv:2411.14317 [pdf, html, other]
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Title: Model-free learning of probability flows: Elucidating the nonequilibrium dynamics of flockingSubjects: Statistical Mechanics (cond-mat.stat-mech); Machine Learning (cs.LG); Probability (math.PR)
Active systems comprise a class of nonequilibrium dynamics in which individual components autonomously dissipate energy. Efforts towards understanding the role played by activity have centered on computation of the entropy production rate (EPR), which quantifies the breakdown of time reversal symmetry. A fundamental difficulty in this program is that high dimensionality of the phase space renders traditional computational techniques infeasible for estimating the EPR. Here, we overcome this challenge with a novel deep learning approach that estimates probability currents directly from stochastic system trajectories. We derive a new physical connection between the probability current and two local definitions of the EPR for inertial systems, which we apply to characterize the departure from equilibrium in a canonical model of flocking. Our results highlight that entropy is produced and consumed on the spatial interface of a flock as the interplay between alignment and fluctuation dynamically creates and annihilates order. By enabling the direct visualization of when and where a given system is out of equilibrium, we anticipate that our methodology will advance the understanding of a broad class of complex nonequilibrium dynamics.
- [64] arXiv:2411.14363 [pdf, html, other]
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Title: Hindered stokesian settling of discs and rodsSubjects: Soft Condensed Matter (cond-mat.soft)
We report measurements of the mean settling velocities for suspensions of discs and rods in the stokes regime for a number of particle aspect ratios. All these shapes display "hindered settling", namely, a decrease in settling speed as the solid volume fraction is increased. A comparison of our data to spheres reveals that discs and rods show less hindering than spheres at the same relative interparticle distance. The data for all six of our particle shapes may be scaled to collapse on that of spheres, with a scaling factor that depends only on the volume of the particle relative to a sphere. Despite the orientational degrees of freedom available with nonspherical particles, it thus appears that the dominant contribution to the hindered settling emerges from terms that are simply proportional to the volume of the sedimenting particles.
- [65] arXiv:2411.14388 [pdf, html, other]
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Title: Ito-Langevin Process for Neutron NoiseComments: 23 pages, 1 figure. Submitted to Progress in Nuclear EnergySubjects: Statistical Mechanics (cond-mat.stat-mech)
We derive an Ito-Langevin stochastic process that captures the time-dependent deviation from Poisson behavior of the noise detected from a general heterogeneous sub-critical neutron system. Using the probability generating function for the actual physical process, we deduce the super-Poisson deviation of the covariance matrix of counts at the detector due to neutron multiplication upon fission. This leads to a general form that coincides with the second moment of an Ito process. This comparison facilitates the formulation of a corresponding effective Langevin equation, which potentially enables simulations that significantly reduce the computational resources required compared to direct simulation of the system's actual noise. This method could assist in designing sub-critical noise experiments for licensing new research reactors, for improving cross-section libraries and for non-destructive assays of spent fuel.
- [66] arXiv:2411.14390 [pdf, html, other]
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Title: Persistent Homology for Structural Characterization in Disordered SystemsComments: 19 pages, 17 figuresSubjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Materials Science (cond-mat.mtrl-sci); Machine Learning (cs.LG); Mathematical Physics (math-ph); Algebraic Topology (math.AT)
We propose a unified framework based on persistent homology (PH) to characterize both local and global structures in disordered systems. It can simultaneously generate local and global descriptors using the same algorithm and data structure, and has shown to be highly effective and interpretable in predicting particle rearrangements and classifying global phases. Based on this framework, we define a non-parametric metric, the Separation Index (SI), which not only outperforms traditional bond-orientational order parameters in phase classification tasks but also establishes a connection between particle environments and the global phase structure. Our methods provide an effective framework for understanding and analyzing the properties of disordered materials, with broad potential applications in materials science and even wider studies of complex systems.
- [67] arXiv:2411.14406 [pdf, html, other]
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Title: Full counting statistics after quantum quenches as hydrodynamic fluctuationsComments: 6+14 pages, 3 figuresSubjects: Statistical Mechanics (cond-mat.stat-mech); Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)
The statistics of fluctuations on large regions of space encodes universal properties of many-body systems. At equilibrium, it is described by thermodynamics. However, away from equilibrium such as after quantum quenches, the fundamental principles are more nebulous. In particular, although exact results have been conjectured in integrable models, a correct understanding of the physics is largely missing. In this letter, we explain these principles, taking the example of the number of particles lying on a large interval in one-dimensional interacting systems. These are based on simple hydrodynamic arguments from the theory of ballistically transported fluctuations, and in particular the Euler-scale transport of long-range correlations. Using these principles, we obtain the full counting statistics (FCS) in terms of thermodynamic and hydrodynamic quantities, whose validity depends on the structure of hydrodynamic modes. In fermionic-statistics interacting integrable models with a continuum of hydrodynamic modes, such as the Lieb-Liniger model for cold atomic gases, the formula reproduces previous conjectures, but is in fact not exact: it gives the correct cumulants up to, including, order 5, while long-range correlations modify higher cumulants. In integrable and non-integrable models with two or less hydrodynamic modes, the formula is expected to give all cumulants.
- [68] arXiv:2411.14408 [pdf, html, other]
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Title: Correlated Structural and Optical Characterization of Hexagonal Boron NitrideJordan A. Gusdorff, Pia Bhatia, Trey T. Shin, Alexandra Sofia Uy-Tioco, Benjamin N. Sailors, Rachael N. Keneipp, Marija Drndić, Lee C. BassettComments: 21 pages, 13 figures, 3 tablesSubjects: Materials Science (cond-mat.mtrl-sci); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)
Hexagonal boron nitride (hBN) hosts quantum emitters that exhibit single-photon emission and spin-dependent fluorescence at room temperature. These features make hBN a promising platform for quantum sensing and photonics. Despite many investigations of their optical properties, the emitters' chemical structure remains unclear, as does the role of contamination at surfaces and interfaces in forming the emitters or modifying their properties. We prepare hBN samples that are compatible with both confocoal photoluminescence microscopy (PL) and transmission electron microscopy (TEM), and we use those techniques to investigate correlations between fluorescent emission, flake morphology, and surface residue. We find that the microscopy techniques themselves induce changes in hBN's optical activity and residue mophology: PL measurements induce photobleaching, whereas TEM measurements alter surface residue and emission characteristics. We also study the effects of common treatments $\unicode{x2014}$ annealing and oxygen plasma cleaning $\unicode{x2014}$ on the structure and optical activity of hBN. The results illustrate the power and importance of correlative studies to elucidate aspects of microscopic mechanisms that influence hBN's functionality as a host for quantum emitters and spin defects.
- [69] arXiv:2411.14413 [pdf, other]
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Title: A Python-Based Approach to Sputter Deposition Simulations in Combinatorial Materials ScienceSubjects: Materials Science (cond-mat.mtrl-sci)
Magnetron sputtering is an essential technique in combinatorial materials science, enabling the efficient synthesis of thin-film materials libraries with continuous compositional gradients. For exploring multidimensional search spaces, minimizing preliminary experiments is essen-tial, as numerous materials libraries are required to adequately cover the space, making it crucial to fabricate only those libraries that are absolutely necessary. This can be achieved by Monte Carlo particle simulations to model the deposition profile, e.g. by SIMTRA, which is an established package mainly designed for single cathode simulations. A strong enhance-ment of its capabilities is the development of a Python-based wrapper, designed to simulate multi-cathode sputter processes through parallel Monte Carlo simulations. By modeling a sputter chamber and determining the relationship between deposition power and rate for an exemplary quaternary system Ni-Pd-Pt-Ru, we achieve a match between simulated and measured compositions, with a mean Euclidean distance of 3.5%. The object-oriented design of the package allows easy customization and enables the definition of complex sputter sys-tems. Due to parallelization, simulating multiple cathodes results in no additional simulation time. These additions extend the capabilities of SIMTRA making it applicable in combinatorial materials research.
- [70] arXiv:2411.14415 [pdf, html, other]
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Title: Ground-state magnetic structures of topological kagome metals RV$_6$Sn$_6$ (R = Tb, Dy, Ho, Er)Yishui Zhou, Min-Kai Lee, Sabreen Hammouda, Sheetal Devi, Shin-Ichiro Yano, Romain Sibille, Oksana Zaharko, Wolfgang Schmidt, Karin Schmalzl, Ketty Beauvois, Eric Ressouche, Po-Chun Chang, Chun-Hao Huang, Lieh-Jeng Chang, Thomas Brückel, Yixi SuComments: To appear in Phys. Rev. ResearchSubjects: Strongly Correlated Electrons (cond-mat.str-el); Materials Science (cond-mat.mtrl-sci)
Magnetic kagome metals have attracted tremendous research interests recently, because they represent an ideal playground for exploring the fascinating interplay between their intrinsically inherited topologically non-trivial electron band structures, magnetism and electronic correlation effects, and the resultant novel electronic/magnetic states and emergent excitations. In this work, we report a comprehensive single-crystal neutron diffraction investigation of the ground-state magnetic structures of the recently discovered V-based topological kagome metals RV$_6$Sn$_6$ (R = Tb, Dy, Ho, Er). Furthermore, the sample synthesis details and our systematic studies of crystal structure, low-temperature magnetic and thermodynamic properties of these compounds via various in-house characterization techniques are also reported. It can be revealed that RV$_6$Sn$_6$ (R = Tb, Dy, Ho) have a collinear ferromagnetic order in the ground state, with the ordered magnetic moment aligned along the c axis for R = Tb, Ho, while approximately 20${^\circ}$ tilted off from the c axis for R = Dy. In contrast, ErV$_6$Sn$_6$ shows an A-type antiferromagnetic structure with a magnetic propagation vector k = (0, 0, 0.5), and with the ordered magnetic moment aligned in the ab plane. A comparison of the low-temperature magnetic structures for both the extensively investigated topological kagome metal series of RV$_6$Sn$_6$ and RMn$_6$Sn$_6$ is given in details. This allows to gain new insights into the complex magnetic interactions, diverse single-ion magnetic anisotropies and spin dynamics in these compounds. The reported ground-state magnetic structures in RV$_6$Sn$_6$ (R = Tb, Dy, Ho, Er) can pave the way for further explorations of the possible interplay between magnetism and topologically non-trivial electron band structures in the magnetically ordered phase regime.
- [71] arXiv:2411.14428 [pdf, other]
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Title: Low-Field Regime of Magnon Transport in Yttrium Iron GarnetHossein Taghinejad, Kohtaro Yamakawa, Xiaoxi Huang, Yuanqi Lyu, Luke P. Cairns, Ramamoorthy Ramesh, James G. AnalytisComments: 25 pages, 5 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
Diffusive propagation of spin waves and their quanta - magnons - in the archetypal magnetic insulator yttrium iron garnet (YIG) is under a surge of research for low-power and low-loss data communication. However, operation under external magnetic fields reduces magnon diffusion length, attenuates the voltage amplitude at measurement terminals, and complicates the architecture of magnonic devices. Here, we explore the low-field and field-free regime of diffusive magnon transport in YIG films. We demonstrate that the field-induced suppression of magnon diffusion length can be fully inhibited only at the zero-field limit. Even a modest field of 10mT attenuates the non-local spin voltage by $\sim$ 20$\%$ in a transport channel of $\sim$ 1$\mu$m long. Using Stoner-Wohlfarth macrospin simulations, we reveal that an often overlooked, in-plane uniaxial anisotropy becomes the critical parameter governing the field-free operation of magnonic devices. We further demonstrate a tenfold enhancement in the effective field associated with the in-plane uniaxial anisotropy of YIG films at low temperatures - a key finding for field-free operation of magnonic devices under cryogenic conditions.
New submissions (showing 71 of 71 entries)
- [72] arXiv:2411.13643 (cross-list from quant-ph) [pdf, html, other]
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Title: Emergent disorder and sub-ballistic dynamics in quantum simulations of the Ising model using Rydberg atom arraysComments: 5 pages, 4 figuresSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech)
Rydberg atom arrays with Van der Waals interactions provide a controllable path to simulate the locally connected transverse-field Ising model (TFIM), a prototypical model in statistical mechanics. Remotely operating the publicly accessible Aquila Rydberg atom array, we experimentally investigate the physics of TFIM far from equilibrium and uncover significant deviations from the theoretical predictions. Rather than the expected ballistic spread of correlations, the Rydberg simulator exhibits a sub-ballistic spread, along with a logarithmic scaling of entanglement entropy in time - all while the system mostly retains its initial magnetization. By modeling the atom motion in tweezer traps, we trace these effects to an emergent natural disorder in Rydberg atom arrays, which we characterize with a minimal random spin model. We further experimentally explore the different dynamical regimes hosted in the system by varying the lattice spacing and the Rabi frequency. Our findings highlight the crucial role of atom motion in the many-body dynamics of Rydberg atom arrays at the TFIM limit, and propose simple benchmark measurements to test for its presence in future experiments.
- [73] arXiv:2411.13645 (cross-list from hep-th) [pdf, other]
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Title: Real-Time Scattering in Ising Field Theory using Matrix Product StatesComments: 16 + 12 pages, many spacetime pictures of scattering processesSubjects: High Energy Physics - Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics - Lattice (hep-lat); Quantum Physics (quant-ph)
We study scattering in Ising Field Theory (IFT) using matrix product states and the time-dependent variational principle. IFT is a one-parameter family of strongly coupled non-integrable quantum field theories in 1+1 dimensions, interpolating between massive free fermion theory and Zamolodchikov's integrable massive $E_8$ theory. Particles in IFT may scatter either elastically or inelastically. In the post-collision wavefunction, particle tracks from all final-state channels occur in superposition; processes of interest can be isolated by projecting the wavefunction onto definite particle sectors, or by evaluating energy density correlation functions. Using numerical simulations we determine the time delay of elastic scattering and the probability of inelastic particle production as a function of collision energy. We also study the mass and width of the lightest resonance near the $E_8$ point in detail. Close to both the free fermion and $E_8$ theories, our results for both elastic and inelastic scattering are in good agreement with expectations from form-factor perturbation theory. Using numerical computations to go beyond the regime accessible by perturbation theory, we find that the high energy behavior of the two-to-two particle scattering probability in IFT is consistent with a conjecture of Zamolodchikov. Our results demonstrate the efficacy of tensor-network methods for simulating the real-time dynamics of strongly coupled quantum field theories in 1+1 dimensions.
- [74] arXiv:2411.13661 (cross-list from quant-ph) [pdf, html, other]
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Title: Non-Bloch self-energy of dissipative interacting fermionsComments: 7+5 pages, 3+1 figuresSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Optics (physics.optics)
The non-Hermitian skin effect describes the phenomenon of exponential localization of single-particle eigenstates near the boundary of the system. We explore its generalization to the many-body regime by investigating interacting fermions in open quantum systems. Therein, the elementary excitations from the ``vacuum'' (steady state) are given by two types of dissipative quasi-particles composed of single-fermion operators. We perturbatively calculate the self-energy of these quasi-particles in the presence of interactions, and utilize the non-Bloch band theory to develop an exact integral formula, which is further simplified by imposing complex momentum conservation. The formula allows calculating the Liouvillian gap modified by interactions with high precision, as demonstrated by comparison to numerical results. Furthermore, our results show that interactions can even enhance the non-reciprocity of fermion hoppings, contrary to the conventional viewpoint from the Pauli exclusion principle. Our formulation provides a quantitative tool for investigating dissipative interacting fermions with non-Hermitian skin effect, and generalizes the Fermi liquid theory to open quantum systems in the context of diagrammatic perturbation theory.
- [75] arXiv:2411.13667 (cross-list from quant-ph) [pdf, html, other]
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Title: Entanglement growth in the dark intervals of a locally monitored free-fermion chainComments: 11 pages, 8 figuresSubjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech)
We consider a free fermionic chain with monitoring of the particle density on a single site of the chain and study the entanglement dynamics of quantum jump trajectories. We show that the entanglement entropy grows in time towards a stationary state which display volume law scaling of the entropy, in stark contrast with both the unitary dynamics after a local quench and the no-click limit corresponding to full post-selection. We explain the extensive entanglement growth as a consequence of the peculiar distribution of quantum jumps in time, which display superpoissonian waiting time distribution characterised by a bunching of quantum jumps followed by long dark intervals where no-clicks are detected, akin to the distribution of fluorescence light in a driven atom. We show that the presence of dark intervals is the key feature to explain the effect and that by increasing the number of sites which are monitored the volume law scaling gives away to the Zeno effect and its associated area law.
- [76] arXiv:2411.13725 (cross-list from physics.comp-ph) [pdf, html, other]
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Title: Renormalization of States and Quasiparticles in Many-body DownfoldingSubjects: Computational Physics (physics.comp-ph); Materials Science (cond-mat.mtrl-sci)
We explore the principles of many-body Hamiltonian complexity reduction via downfolding on an effective low-dimensional representation. We present a unique measure of fidelity between the effective (reduced-rank) description and the full many-body treatment for arbitrary (i.e., ground and excited) states. When the entire problem is mapped on a system of interacting quasiparticles [npj Computational Materials 9 (1), 126, 2023], the effective Hamiltonians can faithfully reproduce the physics only when a clear energy scale separation exists between the subsystems and its environment. We also demonstrate that it is necessary to include quasiparticle renormalization at distinct energy scales, capturing the distinct interaction between subsystems and their surrounding environments. Numerical results from simple, exactly solvable models highlight the limitations and strengths of this approach, particularly for ground and low-lying excited states. This work lays the groundwork for applying dynamical downfolding techniques to problems concerned with (quantum) interfaces.
- [77] arXiv:2411.13737 (cross-list from quant-ph) [pdf, html, other]
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Title: Quantum Friction near the Instability ThresholdSubjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
In this work, we develop an analytical framework to understand quantum friction across distinct stability regimes, providing approximate expressions for frictional forces both in the deep stable regime and near the critical threshold of instability. Our primary finding is analytical proof that, near the instability threshold, the quantum friction force diverges logarithmically. This result, verified through numerical simulations, sheds light on the behavior of frictional instabilities as the system approaches criticality.
Our findings offer new insights into the role of instabilities, critical divergence and temperature in frictional dynamics across quantum and classical regimes. - [78] arXiv:2411.13887 (cross-list from math.AT) [pdf, html, other]
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Title: A cohomology-based Gromov-Hausdorff metric approach for quantifying molecular similarityComments: 14 pages, 3 figuresSubjects: Algebraic Topology (math.AT); Materials Science (cond-mat.mtrl-sci); Computational Geometry (cs.CG); Metric Geometry (math.MG); Machine Learning (stat.ML)
We introduce, for the first time, a cohomology-based Gromov-Hausdorff ultrametric method to analyze 1-dimensional and higher-dimensional (co)homology groups, focusing on loops, voids, and higher-dimensional cavity structures in simplicial complexes, to address typical clustering questions arising in molecular data analysis. The Gromov-Hausdorff distance quantifies the dissimilarity between two metric spaces. In this framework, molecules are represented as simplicial complexes, and their cohomology vector spaces are computed to capture intrinsic topological invariants encoding loop and cavity structures. These vector spaces are equipped with a suitable distance measure, enabling the computation of the Gromov-Hausdorff ultrametric to evaluate structural dissimilarities. We demonstrate the methodology using organic-inorganic halide perovskite (OIHP) structures. The results highlight the effectiveness of this approach in clustering various molecular structures. By incorporating geometric information, our method provides deeper insights compared to traditional persistent homology techniques.
- [79] arXiv:2411.13893 (cross-list from physics.flu-dyn) [pdf, html, other]
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Title: Simulating squirmers with smoothed particle dynamicsComments: 32 pages, 14 figuresSubjects: Fluid Dynamics (physics.flu-dyn); Soft Condensed Matter (cond-mat.soft)
Microswimmers play an important role in shaping the world around us. The squirmer is a simple model for microswimmer whose cilia oscillations on its spherical surface induce an effective slip velocity to propel itself. The rapid development of computational fluid dynamics methods has markedly enhanced our capacity to study the behavior of squirmers in aqueous environments. Nevertheless, a unified methodology that can fully address the complexity of fluid-solid coupling at multiple scales and interface tracking for multiphase flows remains elusive, posing an outstanding challenge to the field. To this end, we investigate the potential of the smoothed particle dynamics (SPD) method as an alternative approach for simulating squirmers. The Lagrangian nature of the method allows it to effectively address the aforementioned difficulty. By introducing a novel treatment of the boundary condition and assigning appropriate slip velocities to the boundary particles, the SPD-squirmer model is able to accurately represent a range of microswimmer types including pushers, neutral swimmers, and pullers. We systematically validate the steady-state velocity of the squirmer, the resulting flow field, its hydrodynamic interactions with the surrounding environment, and the mutual collision of two squirmers. In the presence of Brownian motion, the model is also able to correctly calculate the velocity and angular velocity autocorrelation functions at the mesoscale. Finally, we simulate a squirmer within a multiphase flow by considering a droplet that encloses a squirmer and imposing a surface tension between the two flow phases. We find that the squirmer within the droplet exhibits different motion types.
- [80] arXiv:2411.13936 (cross-list from nlin.PS) [pdf, html, other]
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Title: Formation of nonlinear modes in one-dimensional quasiperiodic lattices with a mobility edgeComments: 13 pages, 7 figures; accepted for Phys. Rev. ASubjects: Pattern Formation and Solitons (nlin.PS); Quantum Gases (cond-mat.quant-gas); Optics (physics.optics)
We investigate the formation of steady states in one-dimensional Bose-Einstein condensates of repulsively interacting ultracold atoms loaded into a quasiperiodic potential created by two incommensurate periodic lattices. We study the transformations between linear and nonlinear modes and describe the general patterns that govern the birth of nonlinear modes emerging in spectral gaps near band edges. We show that nonlinear modes in a symmetric potential undergo both symmetry-breaking pitchfork bifurcations and saddle-node bifurcations, mimicking the prototypical behaviors of symmetric and asymmetric double-well potentials. The properties of the nonlinear modes differ for bifurcations occurring below and above the mobility edge. In the generic case, when the quasiperiodic potential consists of two incommensurate lattices with a nonzero phase shift between them, the formation of localized modes in the spectral gaps occurs through a cascade of saddle-node bifurcations. Because of the analogy between the Gross-Pitaevskii equation and the nonlinear Schrödinger equation, our results can also be applied to optical modes guided by quasiperiodic photonic lattices.
- [81] arXiv:2411.13964 (cross-list from math.PR) [pdf, other]
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Title: Long-time analysis of a pair of on-lattice and continuous run-and-tumble particles with jamming interactionsSubjects: Probability (math.PR); Statistical Mechanics (cond-mat.stat-mech)
Run-and-Tumble Particles (RTPs) are a key model of active matter. They are characterized by alternating phases of linear travel and random direction reshuffling. By this dynamic behavior, they break time reversibility and energy conservation at the microscopic level. It leads to complex out-of-equilibrium phenomena such as collective motion, pattern formation, and motility-induced phase separation (MIPS). In this work, we study two fundamental dynamical models of a pair of RTPs with jamming interactions and provide a rigorous link between their discrete- and continuous-space descriptions. We demonstrate that as the lattice spacing vanishes, the discrete models converge to a continuous RTP model on the torus, described by a Piecewise Deterministic Markov Process (PDMP). This establishes that the invariant measures of the discrete models converge to that of the continuous model, which reveals finite mass at jamming configurations and exponential decay away from them. This indicates effective attraction, which is consistent with MIPS. Furthermore, we quantitatively explore the convergence towards the invariant measure. Such convergence study is critical for understanding and characterizing how MIPS emerges over time. Because RTP systems are non-reversible, usual methods may fail or are limited to qualitative results. Instead, we adopt a coupling approach to obtain more accurate, non-asymptotic bounds on mixing times. The findings thus provide deeper theoretical insights into the mixing times of these RTP systems, revealing the presence of both persistent and diffusive regimes.
- [82] arXiv:2411.13965 (cross-list from q-fin.TR) [pdf, html, other]
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Title: Does the square-root price impact law belong to the strict universal scalings?: quantitative support by a complete survey of the Tokyo stock exchange marketComments: 28 pages, 16 figuresSubjects: Trading and Market Microstructure (q-fin.TR); Statistical Mechanics (cond-mat.stat-mech); General Economics (econ.GN); Portfolio Management (q-fin.PM); Risk Management (q-fin.RM)
Universal power laws have been scrutinised in physics and beyond, and a long-standing debate exists in econophysics regarding the strict universality of the nonlinear price impact, commonly referred to as the square-root law (SRL). The SRL posits that the average price impact $I$ follows a power law with respect to transaction volume $Q$, such that $I(Q) \propto Q^{\delta}$ with $\delta \approx 1/2$. Some researchers argue that the exponent $\delta$ should be system-specific, without universality. Conversely, others contend that $\delta$ should be exactly $1/2$ for all stocks across all countries, implying universality. However, resolving this debate requires high-precision measurements of $\delta$ with errors of around $0.1$ across hundreds of stocks, which has been extremely challenging due to the scarcity of large microscopic datasets -- those that enable tracking the trading behaviour of all individual accounts. Here we conclusively support the universality hypothesis of the SRL by a complete survey of all trading accounts for all liquid stocks on the Tokyo Stock Exchange (TSE) over eight years. Using this comprehensive microscopic dataset, we show that the exponent $\delta$ is equal to $1/2$ within statistical errors at both the individual stock level and the individual trader level. Additionally, we rejected two prominent models supporting the nonuniversality hypothesis: the Gabaix-Gopikrishnan-Plerou-Stanley and the Farmer-Gerig-Lillo-Waelbroeck models. Our work provides exceptionally high-precision evidence for the universality hypothesis in social science and could prove useful in evaluating the price impact by large investors -- an important topic even among practitioners.
- [83] arXiv:2411.14028 (cross-list from math-ph) [pdf, html, other]
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Title: Global well-posedness in a Hartree-Fock model for grapheneComments: 21 pagesSubjects: Mathematical Physics (math-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Analysis of PDEs (math.AP)
Graphene is a monolayer graphitic film where electrons behave like two-dimensional Dirac fermions without mass. Its study has attracted a wide interest in the domain of condensed matter physics. In particular, it represents an ideal system to test the comprehension of 2D massless relativistic particles in a laboratory, the Fermi velocity being $300$ times smaller than the speed of light. In this work, we present a global well-posedness result for graphene in the Hartree-Fock approximation. The model allows to describe the time evolution of graphene in the presence of external electric fields, such as those induced by local defects in the monolayer of carbon atoms. Our approach is based on a well established non-perturbative framework originating from the study of three-dimensional quantum electrodynamics.
- [84] arXiv:2411.14060 (cross-list from physics.app-ph) [pdf, other]
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Title: Tunable Nanostructuring for van der Waals MaterialsGleb Tselikov, Anton Minnekhanov, Georgy Ermolaev, Gleb Tikhonowski, Ivan Kazantsev, Dmitry Dyubo, Daria Panova, Daniil Tselikov, Anton Popov, Arslan Mazitov, Sergei Smirnov, Fedor Lipilin, Umer Ahsan, Nikita Orekhov, Ivan Kruglov, Alexander Syuy, Andrei Kabashin, Boris Chichkov, Zdenek Sofer, Aleksey Arsenin, Kostya Novoselov, Valentyn VolkovComments: 24 pages, 6 figuresSubjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci); Optics (physics.optics)
Van der Waals (vdW) materials are becoming increasingly popular in scientific and industrial applications because of their unique mixture of record electronic, optical, and mechanical properties. However, nanostructuring of vdW materials is still in its infancy and strongly depends on the specific vdW crystal. As a result, the universal self-assembled technology of vdW materials nanostructuring opens vast technological prospects. This work demonstrates an express and universal synthesis method of vdW nanoparticles with well-defined geometry using femtosecond laser ablation and fragmentation. The disarming simplicity of the technique allows us to create nanoparticles from over 50 vdW precursor materials covering transition metal chalcogenides, MXenes, and other vdW materials. Obtained nanoparticles manifest perfectly defined crystalline structures and diverse shapes, from nanospheres to nanocubes and nanotetrahedrons. Thus, our work provides a new paradigm for vdW nanostructuring with a vast potential of tunability for size, shape, and materials specific to the particular application.
- [85] arXiv:2411.14105 (cross-list from math.PR) [pdf, html, other]
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Title: Simultaneous replica-symmetry breaking for vector spin glassesComments: 35 pagesSubjects: Probability (math.PR); Disordered Systems and Neural Networks (cond-mat.dis-nn)
We consider mean-field vector spin glasses with possibly non-convex interactions. Up to a small perturbation of the parameters defining the model, the asymptotic behavior of the Gibbs measure is described in terms of a critical point of an explicit functional. In this paper, we study some properties of these critical points. Under modest assumptions ensuring that different types of spins interact, we show that the replica-symmetry-breaking structures of the different types of spins are in one-to-one correspondence with one another. For instance, if some type of spins displays one level of replica-symmetry breaking, then so do all the other types of spins. This extends the recent results of [Electronic Journal of Probability, 27:1-75, 2022] and [Comm. Math. Phys., 394(3):1101-1152, 2022] that were obtained in the case of multi-species spherical spin glasses with convex interactions.
- [86] arXiv:2411.14146 (cross-list from hep-th) [pdf, html, other]
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Title: One Loop Thermal Effective ActionComments: 48 pagesSubjects: High Energy Physics - Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph)
We compute the one loop effective action for a Quantum Field Theory at finite temperature, in the presence of background gauge fields, employing the Heat-Kernel method. This method enables us to compute the thermal corrections to the Wilson coefficients associated with effective operators up to arbitrary mass dimension, which emerge after integrating out heavy scalars and fermions from a generic UV theory. The Heat-Kernel coefficients are functions of non-zero background `electric', `magnetic' fields, and Polyakov loops. A major application of our formalism is the calculation of the finite temperature Coleman-Weinberg potentials in effective theories, necessary for the study of phase transitions. A novel feature of this work is the systematic calculation of the dependence of Polyakov loops on the thermal factors of Heat-Kernel coefficients and the Coleman-Weinberg potential. We study the effect of Polyakov loop factors on phase transitions and comment on future directions in applications of the results derived in this work.
- [87] arXiv:2411.14180 (cross-list from physics.app-ph) [pdf, html, other]
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Title: Unveiling Ultrafast Spin-Valley Dynamics and Phonon-Mediated Charge Transfer in MoSe$_{2}$/WSe$_{2}$ HeterostructuresJulian Wagner, Robin Bernhardt, Lukas Rieland, Omar Abdul-Aziz, Qiuyang Li, Xiaoyang Zhu, Stefano Dal Conte, Giulio Cerullo, Paul H. M. van Loosdrecht, Hamoon HedayatSubjects: Applied Physics (physics.app-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
We use helicity-resolved ultrafast transient absorption spectroscopy to study spin-valley polarization dynamics in a vertically stacked MoSe$_{2}$/WSe$_{2}$ heterostructure. The experimental findings reveal details of interlayer charge transfer on ultrafast timescales, showing that the spin-valley polarized state of photoexcited carriers is conserved during the charge transfer and formation of interlayer excitons. Our results confirm that phonon scattering mediates the interlayer charge transfer process, while a high phonon population at elevated temperatures causes a significant decrease in spin-valley selective charge transfer. Moreover, the experimental findings demonstrate the possibility that interlayer excitons and their spin-valley polarization can be probed in the optical response of intralayer excitons. These findings pave the way for ultrafast detection, control, and manipulation of spin-valley polarized excitons in transition metal dichalcogenide-based 2D heterostructures.
- [88] arXiv:2411.14204 (cross-list from quant-ph) [pdf, html, other]
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Title: Exact solution for a class of quantum models of interacting bosonsComments: 11 pages, no figuresSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); Mathematical Physics (math-ph); Exactly Solvable and Integrable Systems (nlin.SI)
Quantum models of interacting bosons have wide range of applications, among them the propagation of optical modes in nonlinear media, such as the $k$-photon down conversion. Many of such models are related to nonlinear deformations of finite group algebras, thus, in this sense, they are exactly solvable. Whereas the advanced group-theoretic methods have been developed to study the eigenvalue spectrum of exactly solvable Hamiltonians, in quantum optics the prime interest is not the spectrum of the Hamiltonian, but the evolution of an initial state, such as the generation of optical signal modes by a strong pump mode propagating in a nonlinear medium. I propose a simple and general method of derivation of the solution to such a state evolution problem, applicable to a wide class of quantum models of interacting bosons. For the $k$-photon down conversion model and its generalizations, the solution to the state evolution problem is given in the form of an infinite series expansion in the powers of propagation time with the coefficients defined by a recursion relation with a single polynomial function, unique for each nonlinear model. As an application, I compare the exact solution to the parametric down conversion process with the semiclassical parametric approximation.
- [89] arXiv:2411.14224 (cross-list from cs.ET) [pdf, html, other]
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Title: Thermodynamic Algorithms for Quadratic ProgrammingPatryk-Lipka Bartosik, Kaelan Donatella, Maxwell Aifer, Denis Melanson, Marti Perarnau-Llobet, Nicolas Brunner, Patrick J. ColesComments: 13 pages, 4 figuresSubjects: Emerging Technologies (cs.ET); Statistical Mechanics (cond-mat.stat-mech); Optimization and Control (math.OC)
Thermodynamic computing has emerged as a promising paradigm for accelerating computation by harnessing the thermalization properties of physical systems. This work introduces a novel approach to solving quadratic programming problems using thermodynamic hardware. By incorporating a thermodynamic subroutine for solving linear systems into the interior-point method, we present a hybrid digital-analog algorithm that outperforms traditional digital algorithms in terms of speed. Notably, we achieve a polynomial asymptotic speedup compared to conventional digital approaches. Additionally, we simulate the algorithm for a support vector machine and predict substantial practical speedups with only minimal degradation in solution quality. Finally, we detail how our method can be applied to portfolio optimization and the simulation of nonlinear resistive networks.
- [90] arXiv:2411.14259 (cross-list from quant-ph) [pdf, html, other]
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Title: Addressing the Readout Problem in Quantum Differential Equation Algorithms with Quantum Scientific Machine LearningComments: 5 pages, 4 figuresSubjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Fluid Dynamics (physics.flu-dyn)
Quantum differential equation solvers aim to prepare solutions as $n$-qubit quantum states over a fine grid of $O(2^n)$ points, surpassing the linear scaling of classical solvers. However, unlike classically stored vectors of solutions, the readout of exact quantum states poses a bottleneck due to the complexity of tomography. Here, we show that the readout problem can be addressed with quantum learning tools where we focus on distilling the relevant features. Treating outputs of quantum differential equation solvers as quantum data, we demonstrate that low-dimensional output can be extracted using a measurement operator adapted to detect relevant features. We apply this quantum scientific machine learning approach to classify solutions for shock wave detection and turbulence modeling in scenarios where data samples come directly from quantum differential equation solvers. We show that the basis chosen for performing analysis greatly impacts classification accuracy. Our work opens up the area of research where quantum machine learning for quantum datasets is inherently required.
- [91] arXiv:2411.14261 (cross-list from hep-th) [pdf, html, other]
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Title: On braid statistics versus parastatisticsComments: 11 pages. Based on a plenary talk at ISQS28, Prague, July 1-5, 2024; to appear in the ProceedingsSubjects: High Energy Physics - Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph); Quantum Physics (quant-ph)
I report the recent advances in applying (graded) Hopf algebras with braided tensor product in two scenarios: i) paraparticles beyond bosons and fermions living in any space dimensions and transforming under the permutation group; ii) physical models of anyons living in two space-dimensions and transforming under the braid group. In the first scenario simple toy models based on the so-called $2$-bit parastatistics show that, in the multiparticle sector, certain observables can discriminate paraparticles from ordinary bosons/fermions (thus, providing a counterexample to the widespread belief of the "conventionality of parastatistics" argument). In the second scenario the notion of (braided) Majorana qubit is introduced as the simplest building block to implement the Kitaev's proposal of a topological quantum computer which protects from decoherence.
- [92] arXiv:2411.14324 (cross-list from physics.optics) [pdf, html, other]
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Title: Platinum Black for stray-light mitigation on high-aspect-ratio micromechanical cantileverSubjects: Optics (physics.optics); Materials Science (cond-mat.mtrl-sci)
Microscopic devices are widely used in optomechanical experiments at the cutting-edge of precision experimental physics. Such devices often need to have high electrical conductivity but low reflectivity at optical wavelengths, which can be competing requirements for many commonly available coatings. In this manuscript, we present a technique to electroplate platinum with a highly convoluted surface on a $475\,\mathrm{\mu m } \, \times 500\,\mathrm{\mu m } \, \times 10\,\mathrm{\mu m }$ Silicon/Gold cantilever, preserving its electrical conductivity but reducing its reflectivity in the $0.3 - 1\,\mathrm{\mu m}$ range by a factor of $100$ or greater. The fact that the deposition can be done post-fabrication without damaging delicate structures makes this technique of interest to a potentially large range of experimental applications.
- [93] arXiv:2411.14328 (cross-list from quant-ph) [pdf, html, other]
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Title: An unusual phase transition in a non-Hermitian Su-Schrieffer-Heeger modelSubjects: Quantum Physics (quant-ph); Other Condensed Matter (cond-mat.other)
This article studies a non-Hermitian Su-Schrieffer-Heeger (SSH) model which has periodically staggered Hermitian and non-Hermitian dimers. The changes in topological phases of the considered chiral symmetric model with respect to the introduced non-Hermiticity are studied where we find that the system supports only complex eigenspectra for all values of $u \neq 0$ and it stabilizes only non-trivial insulating phase for higher loss-gain strength. Even if the system acts as a trivial insulator in the Hermitian limit, the increase in loss-gain strength induces phase transition to non-trivial insulating phase through a (gapless) semi-metallic phase. Interesting phenomenon is observed in the case where Hermitian system acts as a non-trivial insulator. In such a situation, the introduced non-Hermiticity neither leaves the non-trivial phase undisturbed nor induces switching to trivial phase. Rather, it shows transition from non-trivial insulating phase to the same where it is mediated by the stabilization of (non-trivial) semi-metallic phase. This unusual transition between the non-trivial insulating phases through non-trivial semi-metallic phase gives rise to a question regarding the topological states of the system under open boundary conditions. So, we analyze the possibility of stable edge states in these two non-trivial insulating phases and check the characteristic difference between them. In addition, we study the nature of topological states in the case of non-trivial gapless (semi-metallic) region.
- [94] arXiv:2411.14357 (cross-list from quant-ph) [pdf, html, other]
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Title: Anomalous transport in U(1)-symmetric quantum circuitsComments: Comments are welcome!Subjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn)
In this work we investigate discrete-time transport in a generic U(1)-symmetric disordered model tuned across an array of different dynamical regimes. We develop an aggregate quantity, a circular statistical moment, which is a simple function of the magnetization profile and which elegantly captures transport properties of the system. From this quantity we extract transport exponents, revealing behaviors across the phase diagram consistent with localized, diffusive, and - most interestingly for a disordered system - superdiffusive regimes. Investigation of this superdiffusive regime reveals the existence of a prethermal "swappy" regime unique to discrete-time systems in which excitations propagate coherently; even in the presence of strong disorder.
- [95] arXiv:2411.14397 (cross-list from quant-ph) [pdf, html, other]
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Title: Discrete Schrodinger equation on graphs: An effective model for branched quantum latticeJournal-ref: EPL 147, 62001 (2024)Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
We propose an approach to quantize discrete networks (graphs with discrete edges). We introduce a new exact solution of discrete Schrodinger equation that is used to write the solution for quantum graphs. Formulation of the problem and derivation of secular equation for arbitrary quantum graphs is presented. Application of the approach for the star graph is demonstrated by obtaining eigenfunctions and eigenvalues explicitely. Practical application of the model in conducting polymers and branched molecular chains is discussed.
Cross submissions (showing 24 of 24 entries)
- [96] arXiv:2201.08856 (replaced) [pdf, html, other]
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Title: Interplay of symmetry breaking and deconfinement in 3D quantum vertex modelsComments: 23 pages, 11 figures, v2: title changed, new vertex model introduced and studied, more detailed discussion of dualities and other mappingsSubjects: Strongly Correlated Electrons (cond-mat.str-el); Statistical Mechanics (cond-mat.stat-mech)
We construct a broad class of frustration-free quantum vertex models in 3+1D whose ground states are weighted superpositions of classical 3D vertex model configurations. Our results are illustrated for diamond, cubic, and BCC lattices, but hold for general 3D lattices with even coordination number. The corresponding classical vertex models have a $\mathbb{Z}_2$ gauge constraint enriched with a $\mathbb{Z}_2$ global symmetry. We study the interplay between these symmetries by exploiting exact wavefunction dualities and effective field theories. We find an exact gapless point which by duality is related to the Rokhsar-Kivelson (RK) point of $U(1)$ quantum spin liquids. At this point, both the symmetry breaking and deconfinement order parameters exhibit long range order. The gapless point is additionally a self-dual point of a second duality that maps the $\mathbb{Z}_2$ deconfined and $\mathbb{Z}_2$ symmetry-broken phases to one another. For the BCC lattice vertex model, we find that gapless point is proximate to an unusual intermediate phase where symmetry breaking and deconfinement coexist.
- [97] arXiv:2303.02029 (replaced) [pdf, html, other]
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Title: Topologically invisible defects in chiral mirror latticesAntonin Coutant, Li-Yang Zheng, Vassos Achilleos, Olivier Richoux, Georgios Theocharis, Vincent PagneuxComments: 9+6 pages, 6+5 figures. Few minor corrections and clarifications. Match published versionJournal-ref: Advanced Physics Research 3 no. 4, (2024) 2300102Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Classical Physics (physics.class-ph); Optics (physics.optics)
One of the hallmark of topological insulators is having conductivity properties that are unaffected by the possible presence of defects. In this work, we go beyond backscattering immunity and obtain topological invisibility across defects or disorder. Using a combination of chiral and mirror symmetry, the transmission coefficient is guaranteed to be unity. Importantly, but no phase shift is induced making the defect completely invisible. Many lattices possess the chiral-mirror symmetry, and we choose to demonstrate the principle on an hexagonal lattice model with Kekule distortion displaying topological edge waves, and we show analytically and numerically that the transmission across symmetry preserving defects is unity. We then realize this lattice in an acoustic system, and confirm the invisibility with numerical experiments. We foresee that the versatility of our model will trigger new experiments to observe topological invisibility in various wave systems, such as photonics, cold atoms or elastic waves.
- [98] arXiv:2308.01726 (replaced) [pdf, html, other]
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Title: Dense Random Packing of Disks With a Power-Law Size Distribution in Thermodynamic Limit: Fractal-like PropertiesComments: 8 pages, 7 figuresJournal-ref: J. Chem. Phys. 160, 024107 (2024)Subjects: Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech)
The correlation properties of a random system of densely packed disks, obeying a power-law size distribution, are analyzed in reciprocal space in the thermodynamic limit. This limit assumes that the total number of disks increases infinitely, while the mean density of the disk centers and the range of the size distribution are kept constant. We investigate the structure factor dependence on momentum transfer across various number of disks and extrapolate these findings to the thermodynamic limit. The fractal power-law decay of the structure factor is recovered in reciprocal space within the fractal range, which corresponds to the range of the size distribution in real space. The fractal exponent coincides with the exponent of the power-law size distribution as was shown previously by the authors [A. Yu. Cherny, E. M. Anitas, V. A. Osipov, J. Chem. Phys. 158, 044114 (2023)]. The dependence of the structure factor on density is examined. As is found, the power-law exponent remains unchanged but the fractal range shrinks when the packing fraction decreases. Additionally, the finite-size effects are studied at extremely low momenta of the order of the inverse system size. We show that the structure factor is parabolic in this region and calculate the prefactor analytically. The obtained results reveal fractal-like properties of the packing and can be used to analyze small-angle scattering from such systems.
- [99] arXiv:2309.05594 (replaced) [pdf, html, other]
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Title: Insulator phases of Bose-Fermi mixtures induced by intraspecies next-neighbor interactionsComments: Substantially updated version that include order parameters for the three new CDW phases found and new figures. 30 pages, 12 figures. Comments are welcomeSubjects: Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)
We study a one-dimensional mixture of two-color fermions and scalar bosons at the hardcore limit, focusing on the effect that the intraspecies next-neighbor interactions have on the zero-temperature ground state of the system for different fillings of each carrier. Exploring the problem's parameters, we observed that the non-local interaction could favor or harm the well-known mixed Mott and spin-selective Mott insulators. We also found the emergence of three unusual insulating states with charge density wave (CDW) structures in which the orders of the carriers are out of phase with each other. For instance, the immiscible CDW appears only at half-filling bosonic density, whereas the mixed CDW state is characterized by equal densities of bosons and fermions. Finally, the spin-selective CDW couples the bosons and only one kind of fermions. Appropriate order parameters were proposed for each phase to obtain the critical parameters for the corresponding superfluid-insulator transition. Our results can inspire or contribute to understanding experiments in cold-atom setups with long-range interactions or recent reports involving quasiparticles in semiconductor heterostructures.
- [100] arXiv:2310.07843 (replaced) [pdf, html, other]
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Title: Ductile and brittle yielding of athermal amorphous solids: a mean-field paradigm beyond the random field Ising modelComments: 40 pages, 43 figuresJournal-ref: Phys. Rev. E 110, 045002 (2024)Subjects: Soft Condensed Matter (cond-mat.soft); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech)
Developing a unified theory describing both ductile and brittle yielding constitutes a fundamental challenge of non-equilibrium statistical physics. Recently, it has been proposed that the nature of the yielding transition is controlled by physics akin to that of the quasistatically driven Random field Ising model (RFIM), which has served as the paradigm for understanding the effect of quenched disorder in slowly driven systems with short-ranged interactions. However, this theoretical picture neglects both the dynamics of, and the elasticity-induced long-ranged interactions between, the mesoscopic material constituents. Here, we address these two aspects and provide a unified theory building on the Hébraud-Lequeux elastoplastic description. The first aspect is crucial to understanding the competition between the imposed deformation rate and the finite timescale of plastic rearrangements: we provide a dynamical description of the macroscopic stress drop and predictions for the divergence of the peak susceptibility with inverse shear rate. The second is essential in order to capture properly the behaviour in the limit of quasistatic driving, where avalanches of plasticity diverge with system size at any value of the strain. We fully characterise the avalanche behaviour, which is radically different to that of the RFIM. In the quasistatic, infinite size limit, we find that both models have mean-field Landau exponents, obscuring the effect of the interactions. We show, however, that the latter profoundly affect the behaviour of finite systems approaching the spinodal-like brittle yield point, where we recover qualitatively the finite-size trends found in particle simulations, and modify the nature of the random critical point separating ductile and brittle yielding, where we predict critical behaviour on top of the marginality present at any value of the strain.
- [101] arXiv:2310.14244 (replaced) [pdf, html, other]
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Title: Exact semiclassical dynamics of generic Lipkin-Meshkov-Glick modelComments: 12 pages, 10 figuresSubjects: Quantum Gases (cond-mat.quant-gas); Exactly Solvable and Integrable Systems (nlin.SI)
Lipkin-Meshkov-Glick model is paradigmatic to study quantum phase transition in equilibrium or non-equilibrium systems and entanglement dynamics for a variety of disciplines. In thermodynamics limit, quantum fluctuations are negligible, its semiclassical dynamics in presence of only one nonlinear couplings, as a good benchmark to study quantum fluctuation in finite-size system, can be well obtained in terms of Jacobi elliptic functions. In this work, we extend this semiclassical analysis into the regime where both nonlinear interactions are present, and successfully obtain its exact solutions of semiclassical equations by constructing an auxiliary function that is a linear combination of the $y$ and $z$ component of the classical spin in thermodynamic limit. Taking implementation of Lipkin-Meshkov-Glick model in a Bose-Einstein condensate setup as an example, we figure out all classical dynamical modes, specially find out mesoscopic self-trapping mode in population and phase-difference space even persists in presence of both nonlinear couplings. Our results would be useful to analyze dynamical phase transitions and entanglement dynamics of Lipkin-Meshkov-Glick model in presence of both nonlinear couplings.
- [102] arXiv:2312.01914 (replaced) [pdf, other]
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Title: Thermodynamic signatures of a potential Fulde-Ferrell-Larkin Ovchinnikov state in the isotropic superconductor Ti4Ir2OSubjects: Superconductivity (cond-mat.supr-con)
This study presents an investigation of the isotropic superconductor Ti4Ir2O, focusing on its magnetic field vs. temperature phase diagram near and above the Pauli limit for superconductivity. The data exhibits characteristic features that align with the formation of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, including a deviation of the upper critical field line from the standard WHH model upon approaching the Pauli limiting field and a phase transition line separating the ordinary low-field superconducting phase from an unusual high field superconducting state above the Pauli limit. We discuss why the upper critical field line in this isotropic superconductor can approach the Pauli limit, necessitating a particularly high orbital limit for superconductivity. The research also identifies peculiar features in the specific heat data set taken at 0.6 K, which may be an example of the segmentation of the FFLO phase with multiple q phases. The findings provide an explanation for the violation of the Pauli limit in this superconductor, adding a fully isotropic superconductor to the list of potential FFLO superconductors and providing new insights for contemporary theories of the FFLO state.
- [103] arXiv:2312.03215 (replaced) [pdf, other]
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Title: Evidence for the novel type of orbital Fulde-Ferrell-Larkin-Ovchinnikov state in the bulk limit of 2H-NbSe2Chang-woo Cho, Kwan To Lo, Cheuk Yin Ng, Timothée T. Lortz, Abdel Rahman Allan, Mahmoud Abdel-Hafiez, Jaemun Park, Beopgil Cho, Keeseong Park, Noah F. Q. Yuan, Rolf LortzSubjects: Superconductivity (cond-mat.supr-con)
The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, an unusual superconducting state, defies high magnetic fields beyond the Pauli paramagnetic limit. It exhibits a spatial modulation of the superconducting order parameter in real space and is exceptionally rare. Recently, an even more exotic variant - the orbital FFLO state - was predicted and identified in the transition metal dichalcogenide superconductor 2H-NbSe2. This state emerges in thin samples with thicknesses below ~40 nm, at the boundary between two and three dimensions. The complex interplay between Ising spin orbit coupling and the Pauli paramagnetic effect can lead to a stabilization of the FFLO state in a relatively large range of the magnetic phase diagram, even well below the Pauli limit. In this study, we present experimental evidence of the formation of this orbital FFLO state in bulk 2H-NbSe2 samples. This evidence was obtained using high-resolution DC magnetization and magnetic torque experiments in magnetic fields applied strictly parallel to the NbSe2 basal plane. Both quantities display a crossover to a discontinuous first-order superconducting transition at the normal state boundary in magnetic fields of 4 T and above. This is usually seen as a sign that Pauli paramagnetic pair breaking effects affect the superconducting state. The magnetic torque reveals a small step-like reversible anomaly, indicating a magnetic field-induced thermodynamic phase transition within the superconducting state. This anomaly bears many similarities to the FFLO transitions in other FFLO superconductors, suggesting the potential existence of an orbital FFLO state in bulk 2H-NbSe2 samples. Additionally, we observe a pronounced in-plane 6-fold symmetry of the upper critical field in the field range above this phase transition, which has previously been interpreted as a hallmark of the orbital FFLO state in thin 2H-NbSe2.
- [104] arXiv:2402.00272 (replaced) [pdf, other]
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Title: Quantum phase transitions and composite excitations of antiferromagnetic spin trimer chains in a magnetic fieldComments: 15+6 pages, 16 figures, to be published in npj Quantum materialsSubjects: Strongly Correlated Electrons (cond-mat.str-el); Computational Physics (physics.comp-ph)
Motivated by recent advancements in theoretical and experimental studies of the high-energy excitations on an antiferromagnetic trimer chain, we numerically investigate the quantum phase transition and composite dynamics in this system by applying a magnetic field. The numerical methods we used include the exact diagonalization, density matrix renormalization group, time-dependent variational principle, and cluster perturbation theory. From calculating the entanglement entropy, we have revealed the phase diagram which includes the XY-I, $1/3$ magnetization plateau, XY-II, and ferromagnetic phases. Both the critical XY-I and XY-II phases are characterized by the conformal field theory with a central charge $c \simeq 1$. By analyzing the dynamic spin structure factor, we elucidate the distinct features of spin dynamics across different phases. In the regime with weak intertrimer interaction, we identify the intermediate-energy and high-energy modes in the XY-I and $1/3$ magnetization plateau phases as internal trimer excitations, corresponding to the propagating of doublons and quartons, respectively. Notably, applying a magnetic field splits the high-energy spectrum into two branches, labeled as the upper quarton and lower quarton. Furthermore, we explore the spin dynamics of a frustrated trimerized model closely related to the quantum magnet \ce{Na_2Cu_3Ge_4O_12}. In the end, we extend our discuss on the possibility of the quarton Bose-Einstein condensation in the trimer systems. Our results are expected to be further verified through the inelastic neutron scattering and resonant inelastic X-ray scattering, and also provide valuable insights for exploring high-energy exotic excitations.
- [105] arXiv:2402.14104 (replaced) [pdf, html, other]
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Title: Universal Density Shift Coefficients for the Thermal Conductivity and Shear Viscosity of a Unitary Fermi GasComments: 15 pages 12 figuresJournal-ref: PhysRevResearch.6.L042021(2024)Subjects: Quantum Gases (cond-mat.quant-gas)
We measure universal temperature-independent density shifts for the thermal conductivity $\kappa_T$ and shear viscosity $\eta$, relative to the high temperature limits, for a normal phase unitary Fermi gas confined in a box potential. We show that a time-dependent kinetic theory model enables extraction of the hydrodynamic transport times $\tau_\eta$ and $\tau_\kappa$ from the time-dependent free-decay of a spatially periodic density perturbation, yielding the static transport properties and density shifts, corrected for finite relaxation times.
- [106] arXiv:2402.19244 (replaced) [pdf, html, other]
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Title: Electron conductance and many-body marker of a cavity-embedded topological 1D chainJournal-ref: Phys. Rev. B 110, 195416 (2024) (Editors' Suggestion)Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Other Condensed Matter (cond-mat.other); Quantum Physics (quant-ph)
We investigate many-body topological and transport properties of a one-dimensional Su-Schrieffer-Heeger (SSH) topological chain coupled to the quantum field of a cavity mode. The quantum conductance is determined via Green's function formalism in terms of the light-matter eigenstates calculated via exact diagonalization for a finite number of electrons. We show that the topology of the cavity-embedded many-electron system is described by a generalized electron-photon Zak marker. We reveal how the quantization of transport is modified by the cavity vacuum fields for a finite-size chain and how it is impacted by electronic disorder. Moreover, we show that electron-photon entanglement produces dramatic differences with respect to the predictions of mean-field theory, which strongly underestimates cavity-modified transport.
- [107] arXiv:2404.08782 (replaced) [pdf, html, other]
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Title: Phase transitions of correlated systems from graph neural networks with quantum embedding techniquesComments: 12 pages, 4 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el); Materials Science (cond-mat.mtrl-sci); Computational Physics (physics.comp-ph)
Correlated systems represent a class of materials that are difficult to describe through traditional electronic structure methods. The computational demand to simulate the structural dynamics of such systems, with correlation effects considered, is substantial. Here, we investigate the structural dynamics of $f$- and $d$-electron correlated systems by integrating quantum embedding techniques with interatomic potentials derived from graph neural networks. For Cerium, a prototypical correlated $f$-electron system, we use Density Functional Theory with the Gutzwiller approximation to generate training data due to efficiency with which correlations effects are included for large multi-orbital systems. For Nickel Oxide, a prototypical correlated $d$-electron system, advancements in computational capabilities now permit the use of full Dynamical Mean Field Theory to obtain energies and forces. We train neural networks on this data to create a model of the potential energy surface, enabling rapid and effective exploration of structural dynamics. Utilizing these potentials, we delineate transition pathways between the $\alpha$, $\alpha'$, and $\alpha''$ phases of Cerium and predict the melting curve of Nickel Oxide. Our results demonstrate the potential of machine learning potentials to accelerate the study of strongly correlated systems, offering a scalable approach to explore and understand the complex physics governing these materials.
- [108] arXiv:2404.17410 (replaced) [pdf, html, other]
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Title: Scattered waves fuel emergent activitySubjects: Soft Condensed Matter (cond-mat.soft)
Active matter taps into external energy sources to power its own processes. Systems of passive particles ordinarily lack this capacity, but can become active if the constituent particles interact with each other nonreciprocally. By reformulating the theory of classical wave-matter interactions, we demonstrate that interactions mediated by scattered waves generally are not constrained by Newton's third law. The resulting center-of-mass forces propel clusters of scatterers, enabling them to extract energy from the wave and rendering them active. This form of activity is an emergent property of the scatterers' state of organization and can arise in any system where mobile objects scatter waves. Emergent activity flips the script on conventional active matter whose nonreciprocity emerges from its activity, and not the other way around. We combine theory, experiment and simulation to illustrate how emergent activity arises in wave-matter composite systems and to explore the phenomenology of emergent activity in experimentally accessible models. These preliminary studies suggest that heterogeneity is a singular perturbation to the dynamics of wave-matter composite systems, and induces emergent activity under all but the most limited circumstances.
- [109] arXiv:2405.05882 (replaced) [pdf, html, other]
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Title: Nonlinear conductivity of aqueous electrolytes: beyond the first Wien effectJournal-ref: J. Chem. Phys. 161, 184504 (2024)Subjects: Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech)
The conductivity of strong electrolytes increases under high electric fields, a nonlinear response known as the first Wien effect. Here, using molecular dynamics simulations we show that this increase is almost suppressed in moderately concentrated aqueous electrolytes due to the alignment of the water molecules by the electric field. As a consequence of this alignement, the permittivity of water decreases and becomes anisotropic, an effect which can be measured in simulations and reproduced by a model of water molecules as dipoles. We incorporate the resulting anisotropic interactions between the ions into a Stochastic Density Field Theory and calculate ionic correlations as well as corrections to the Nernst-Einstein conductivity, which are in qualitative agreement with the numerical simulations.
- [110] arXiv:2405.09217 (replaced) [pdf, html, other]
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Title: Augmenting Density Matrix Renormalization Group with Clifford CircuitsSubjects: Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)
Density Matrix Renormalization Group (DMRG) or Matrix Product States (MPS) are widely acknowledged as highly effective and accurate methods for solving one-dimensional quantum many-body systems. However, the direct application of DMRG to the study two-dimensional systems encounters challenges due to the limited entanglement encoded in the wave-function ansatz. Conversely, Clifford circuits offer a promising avenue for simulating states with substantial entanglement, albeit confined to stabilizer states. In this work, we present the seamless integration of Clifford circuits within the DMRG algorithm, leveraging the advantages of both Clifford circuits and DMRG. This integration leads to a significant enhancement in simulation accuracy with small additional computational cost. Moreover, this framework is useful not only for its current application but also for its potential to be easily adapted to various other numerical approaches
- [111] arXiv:2406.03896 (replaced) [pdf, html, other]
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Title: Data-driven discovery of self-similarity using neural networksComments: 21 pages, 18 figures, 5 tablesSubjects: Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech); Machine Learning (cs.LG)
Finding self-similarity is a key step for understanding the governing law behind complex physical phenomena. Traditional methods for identifying self-similarity often rely on specific models, which can introduce significant bias. In this paper, we present a novel neural network-based approach that discovers self-similarity directly from observed data, without presupposing any models. The presence of self-similar solutions in a physical problem signals that the governing law contains a function whose arguments are given by power-law monomials of physical parameters, which are characterized by power-law exponents. The basic idea is to enforce such particular forms structurally in a neural network in a parametrized way. We train the neural network model using the observed data, and when the training is successful, we can extract the power exponents that characterize scale-transformation symmetries of the physical problem. We demonstrate the effectiveness of our method with both synthetic and experimental data, validating its potential as a robust, model-independent tool for exploring self-similarity in complex systems.
- [112] arXiv:2406.17417 (replaced) [pdf, html, other]
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Title: Plaquette-type valence bond solid state in the $J_1$-$J_2$ square-lattice Heisenberg modeComments: close to the published versionJournal-ref: Phys.Rev.B 110,195111 (2024)Subjects: Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)
We utilize Density Matrix Renormalization Group (DMRG) and Fully Augmented Matrix Product States (FAMPS) methods to investigate the Valence Bond Solid (VBS) phase in the $J_1$-$J_2$ square lattice Heisenberg model. To differentiate between the Columnar Valence Bond Solid (CVBS) and Plaquette Valence Bond Solid (PVBS) phases, we introduce an anisotropy $\Delta_y$ in the nearest neighboring coupling in the $y$-direction, aiming at detecting the possible spontaneous rotational symmetry breaking in the VBS phase. In the calculations, we push the bond dimension to as large as $D = 25000$ in FAMPS, simulating systems at a maximum size of $14 \times 14$. With a careful extrapolation of the truncation errors and appropriate finite-size scaling, followed by finite $\Delta_y$ scaling analysis of the VBS dimer order parameters, we identify the VBS phase as a PVBS type, meaning there is no spontaneous rotational symmetry breaking in the VBS phase. This study not only resolves the long-standing issue of the characterization of the VBS order in the $J_1$-$J_2$ square lattice Heisenberg model but also highlights the capabilities of FAMPS in the study of two-dimensional quantum many-body systems.
- [113] arXiv:2406.17997 (replaced) [pdf, html, other]
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Title: The dynamics of Tonks-Girardeau gas excited by a pulse driveComments: 9 pages, 6 figuresSubjects: Quantum Gases (cond-mat.quant-gas)
In this paper we study the dynamics of Tonks-Girardeau (TG) gases in a harmonic potential driven by Gaussian pulse, which is a correspondence of the excitation dynamics of electrons in matters driven by ultrashort laser pulse. The evolving dynamics of TG gas are obtained with Bose-Fermi mapping method combined with the numerical techniques. We calculate the evolving dynamics of occupation distribution of single-particle energy levels, density distribution and momentum distribution of the system. It is shown that the system arrived at a dynamically stable state at the end of driving. At high-frequency regime TG gases return back to ground state while at low-frequency regime the population inversion exhibits and all atoms occupy high levels.
- [114] arXiv:2406.18649 (replaced) [pdf, html, other]
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Title: [111]-strained spin ice: Localization of thermodynamically deconfined monopolesComments: 17 pages, 13 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el); Statistical Mechanics (cond-mat.stat-mech)
We study classical spin ice under uniaxial strain along the $[111]$ crystallographic axis. Remarkably, such strain preserves the extensive ice degeneracy and the corresponding classical Coulomb phase. The emergent monopole excitations remain thermodynamically deconfined exactly as in the isotropic case. However, their motion under local heat bath dynamics depends qualitatively on the sign of the strain. In the low-temperature limit for negative strain, the monopoles diffuse, while for positive strain, they localize. Introducing additional ring exchange dynamics into the ice background transforms the localized monopoles into sub-dimensional excitations whose motion is restricted to diffusion in the $(111)$-plane. The phenomena we identify are experimentally accessible in rare-earth pyrochlores under uniaxial pressure as well as in tripod kagome materials. The diffusive versus localized nature of the monopoles manifests in characteristic magnetic noise spectra, which we compute.
- [115] arXiv:2407.14583 (replaced) [pdf, html, other]
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Title: Correlated Topological Mixed-Valence Insulators in Moir\'e Hetero-BilayersComments: Main text: 7 pages, 3 figures, Supplementary information: 3 pagesJournal-ref: Phys. Rev. B 110, L201105, 2024Subjects: Strongly Correlated Electrons (cond-mat.str-el)
Moiré transition metal dichalcogenide (TMD) materials provide an ideal playground for studying the combined interplay of strong interactions and band-topology over a range of electronic fillings. Here we investigate the panoply of interaction-induced electronic phases that arise at a total commensurate filling of $\nu_T=2$ in moiré TMD heterobilayers, focusing specifically on their renormalized band-topology. We carry out a comprehensive self-consistent parton mean-field analysis on an interacting mixed-valence Hamiltonian describing AB-stacked MoTe$_2$/WSe$_2$ to highlight different ingredients that arise due to "Mottness", band-flattening, an enhanced excitonic tendency, and band-inversion, leading to correlated topological semi-metals and insulators. We also propose a possible route towards realizing fractionalized insulators with emergent neutral fermionic excitations in this and other closely related platforms.
- [116] arXiv:2408.03769 (replaced) [pdf, html, other]
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Title: Nadaraya-Watson kernel smoothing as a random energy modelComments: 10 pages, 3 figuresSubjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Machine Learning (stat.ML)
Precise asymptotics have revealed many surprises in high-dimensional regression. These advances, however, have not extended to perhaps the simplest estimator: direct Nadaraya-Watson (NW) kernel smoothing. Here, we describe how one can use ideas from the analysis of the random energy model (REM) in statistical physics to compute sharp asymptotics for the NW estimator when the sample size is exponential in the dimension. As a simple starting point for investigation, we focus on the case in which one aims to estimate a single-index target function using a radial basis function kernel on the sphere. Our main result is a pointwise asymptotic for the NW predictor, showing that it re-scales the argument of the true link function. Our work provides a first step towards a detailed understanding of kernel smoothing in high dimensions.
- [117] arXiv:2408.11731 (replaced) [pdf, html, other]
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Title: Phase diagram of a spin-1/2 Heisenberg ladder with a chirality-chirality interactionComments: 16 pages, 13 figures. arXiv admin note: text overlap with arXiv:2311.07053Subjects: Strongly Correlated Electrons (cond-mat.str-el); Statistical Mechanics (cond-mat.stat-mech)
A spin-1/2 Heisenberg model with a chirality-chirality interaction (CCI) on a two-leg ladder provides a minimal setup to explore an interplay between spin and chirality degrees of freedom. This model is potentially relevant for understanding the effects of a four-spin ring exchange and a phonon-mediated interaction on a ladder. By applying the Abelian bosonization and two types of spin-chirality duality, we derive a comprehensive ground-state phase diagram that includes previously unexplored cases of a ferromagnetic rung exchange $J_\perp<0$ or a negative CCI $K_{\rm ch}<0$. The phase diagram consists of the rung singlet (RS) phase, the Haldane phase, and three non-magnetic ordered phases. Moreover, the RS and Haldane phases consist of several regions with different dominant correlations in terms of spin, dimer, or chirality. We perform numerical simulations to confirm the predicted phase structure and critical properties.
- [118] arXiv:2408.13111 (replaced) [pdf, html, other]
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Title: Time series forecasting of multiphase microstructure evolution using deep learningJournal-ref: Computational Materials Science 247, 113518, 2025Subjects: Materials Science (cond-mat.mtrl-sci)
Microstructure evolution, which plays a critical role in determining materials properties, is commonly simulated by the high-fidelity but computationally expensive phase-field method. To address this, we approximate microstructure evolution as a time series forecasting problem within the domain of deep learning. Our approach involves implementing a cost-effective surrogate model that accurately predicts the spatiotemporal evolution of microstructures, taking an example of spinodal decomposition in binary and ternary mixtures. Our surrogate model combines a convolutional autoencoder to reduce the dimensional representation of these microstructures with convolutional recurrent neural networks to forecast their temporal evolution. We use different variants of recurrent neural networks to compare their efficacy in developing surrogate models for phase-field predictions. On average, our deep learning framework demonstrates excellent accuracy and speedup relative to the "ground truth" phase-field simulations. We use quantitative measures to demonstrate how surrogate model predictions can effectively replace the phase-field timesteps without compromising accuracy in predicting the long-term evolution trajectory. Additionally, by emulating a transfer learning approach, our framework performs satisfactorily in predicting new microstructures resulting from alloy composition and physics unknown to the model. Therefore, our approach offers a useful data-driven alternative and accelerator to the materials microstructure simulation workflow.
- [119] arXiv:2408.15835 (replaced) [pdf, html, other]
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Title: Neural density functional theory of liquid-gas phase coexistenceComments: 23 pages, 9 figuresSubjects: Soft Condensed Matter (cond-mat.soft)
We use supervised machine learning together with the concepts of classical density functional theory to investigate the effects of interparticle attraction on the pair structure, thermodynamics, bulk liquid-gas coexistence, and associated interfacial phenomena in many-body systems. Local learning of the one-body direct correlation functional is based on Monte Carlo simulations of inhomogeneous systems with randomized thermodynamic conditions, randomized planar shapes of the external potential, and randomized box sizes. Focusing on the prototypical Lennard-Jones system, we test predictions of the resulting neural attractive density functional across a broad spectrum of physical behavior associated with liquid-gas phase coexistence in bulk and at interfaces. We analyse the bulk radial distribution function $g(r)$ obtained from automatic differentiation and the Ornstein-Zernike route and determine i) the Fisher-Widom line, i.e. the crossover of the asymptotic (large distance) decay of $g(r)$ from monotonic to oscillatory, ii) the (Widom) line of maximal correlation length, iii) the line of maximal isothermal compressibility and iv) the spinodal by calculating the poles of the structure factor in the complex plane. The bulk binodal and the density profile of the free liquid-gas interface are obtained from density functional minimization and the corresponding surface tension from functional line integration. We also show that the neural functional describes accurately the phenomena of drying at a hard wall and of capillary evaporation for a liquid confined in a slit pore. Our neural framework yields results that improve significantly upon standard mean-field treatments of interparticle attraction. Comparison with independent simulation results demonstrates a consistent picture of phase separation even when restricting the training to supercritical states only.
- [120] arXiv:2409.09562 (replaced) [pdf, html, other]
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Title: Inverted duality of Hubbard model and an equation for the Green's functionComments: 6 pages, 2 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el)
The Hubbard model, a cornerstone in the field of condensed matter physics, serves as a fundamental framework for investigating the behavior of strongly correlated electron systems. This paper presents a novel perspective on the model, uncovering its inherent inverted duality which has profound implications for our comprehension of this complex system. Taking advantage of this special mathematical property, we have formulated an equation that the electron Green's function must satisfy. Our findings pave the way for further exploration and potentially new insights into the dynamics of electron correlations and phase transitions in the Hubbard model.
- [121] arXiv:2410.03256 (replaced) [pdf, html, other]
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Title: Reducing disorder in Ge quantum wells by using thick SiGe barriersDavide Costa, Lucas E. A. Stehouwer, Yi Huang, Sara Martí-Sánchez, Davide Degli Esposti, Jordi Arbiol, Giordano ScappucciSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci)
We investigate the disorder properties of two-dimensional hole gases in Ge/SiGe heterostructures grown on Ge wafers, using thick SiGe barriers to mitigate the influence of the semiconductor-dielectric interface. Across several heterostructure field effect transistors we measure an average maximum mobility of $(4.4 \pm 0.2) \times 10^{6}~\mathrm{cm^2/Vs}$ at a saturation density of $(1.72 \pm 0.03) \times 10^{11}~\mathrm{cm^{-2}}$, corresponding to a long mean free path of $(30 \pm 1)~\mathrm{\mu m}$. The highest measured mobility is $4.68 \times 10^{6}~\mathrm{cm^2/Vs}$. We identify uniform background impurities and interface roughness as the dominant scattering mechanisms limiting mobility in a representative device, and we evaluate a percolation-induced critical density of $(4.5 \pm 0.1)\times 10^{9} ~\mathrm{cm^{-2}}$. This low-disorder heterostructure, according to simulations, may support the electrostatic confinement of holes in gate-defined quantum dots.
- [122] arXiv:2410.03332 (replaced) [pdf, other]
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Title: Site-projected Thermal Conductivity: Application to defects, interfaces, and homogeneously disordered materialsComments: 7 pages, 8 figures, Accepted for PSS (RRL)Subjects: Materials Science (cond-mat.mtrl-sci)
With the rapid advance of high-performance computing and electronic technologies, understanding thermal conductivity in materials has become increasingly important. This study presents a novel method: the Site-projected Thermal Conductivity (SPTC) that quantitatively estimates the local (atomic) contribution to heat transport, leveraging the Green-Kubo thermal transport equations. We demonstrate the effectiveness of this approach on disordered and amorphous graphene, amorphous silicon, and grain boundaries in silicon-germanium alloys. Amorphous graphene reveals a percolation behavior for thermal transport. The results highlight the potential of our method to provide new insights into the thermal behavior of materials, offering a promising avenue for materials design and performance optimization.
- [123] arXiv:2410.08887 (replaced) [pdf, html, other]
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Title: How Semilocal Are Semilocal Density Functional Approximations? -Tackling Self-Interaction Error in One-Electron SystemsSubjects: Materials Science (cond-mat.mtrl-sci); Chemical Physics (physics.chem-ph)
Self-interaction error (SIE), arising from the imperfect cancellation of the spurious classical Coulomb interaction between an electron and itself, is a persistent challenge in modern density functional approximations. This issue is illustrated using the prototypical one-electron system $H_2^+$. While significant efforts have been made to eliminate SIE through the development of computationally expensive nonlocal density functionals, it is equally important to explore whether SIE can be mitigated within the framework of more efficient semilocal density functionals. In this study, we present a non-empirical meta-generalized gradient approximation (meta-GGA) that incorporates the Laplacian of the electron density. Our results demonstrate that the meta-GGA significantly reduces SIE, yielding a binding energy curve for $H_2^+$ that matches the exact solution at equilibrium and improves across a broad range of bond lengths over those of the Perdew-Burke-Ernzerhof (PBE) and strongly-constrained and appropriately-normed (SCAN) semilocal density functionals. This advancement paves the way for further development within the realm of semilocal approximations.
- [124] arXiv:2410.12041 (replaced) [pdf, other]
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Title: Tuning Electric Polarization via Exchange Striction Interaction in CaMn$_7$O$_{12}$ by Sr-DopingA. Nonato, S. Y. Vilar, J. Mira, María A. Señarís-Rodríguez, Manuel Sánchez andújar, J. Agostinho Moreira, A. Almeida, R. X. Silva, C.W.A. PaschoalSubjects: Materials Science (cond-mat.mtrl-sci); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Magnetoelectric (ME) materials displaying strong magnetically induced polarization have attracted considerable interest due to their potential applications in spintronics and various fast electrically controlled magnetic devices. CaMn$_7$O$_{12}$ (CMO) stands out for its giant spin-induced ferroelectric polarization. However, the origin of the induced electric polarization in CMO remains highly controversial and continues to be a subject of ongoing debate. In this paper, through room temperature X-ray powder diffraction (XRPD), temperature-dependent magnetic susceptibility, and thermally stimulated depolarizing current (TSDC) measurements, we provide experimental evidence for a route to tune the magnetically induced polarization by modifying the exchange-striction in CMO via Sr-doping. Our findings demonstrate that the large and broad current peaks observed near the first magnetic phase transition ($T_N1 \sim 90$ K) indicate contributions to the TSDC density from both extrinsic thermally stimulated depolarization processes and intrinsic pyroelectric current arising from magnetically induced polarization changes. We suggest that this reduction in induced electric polarization in CMO originates from the increase in the Mn$^{3+}$ -- O -- Mn$^{4+}$ bond angle due to Sr$^{2+}$ doping, weakening the exchange-striction interaction. Meanwhile, the Dzyaloshinskii-Moriya (DM) effect determines the direction of the induced electric polarization. Our result sheds light on understanding the intriguing giant-induced polarization in CMO and similar compounds with complex magnetic structures.
- [125] arXiv:2410.12486 (replaced) [pdf, other]
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Title: Phase transformation kinetics in polycrystalline Fe_xAl_1-x (x>0.6) alloys: Experiment and SimulationArtem A. Nazarov, Igor Y. Pashenkin, Dmitry A. Tatarskiy, Pavel A. Yunin, Sergey A. Churin, Maksim V. Sapozhnikov, Andrey A. Fraerman, Murtaza Bohra, Nikolay I. PolushkinComments: 7 pages, 4 figures, 1 tableSubjects: Materials Science (cond-mat.mtrl-sci)
The presence of defects of different kinds, e.g., vacancies, voids, dislocations, grain boundaries, and surfaces, in realistic materials can strongly modify and even dictate the thermodynamics of phase transformations. Our study demonstrates, both theoretically and experimentally, that in the ordering of Fe_xAl_1-x (x>0.6) alloys subjected to high-temperature treatment, the relaxation of the as-prepared chemically disordered alloy into the ordered B2 state is hampered by another process. A manifestation of this is an increase in the alloy's magnetization. A plausible explanation for a non-monotonous behavior of the magnetization we observe is segregation of Al into structural defects, e.g., grain boundaries, and thus purification of the Fe host lattice. Qualitatively, experimental findings reported here are supported by molecular dynamics simulation of the phase transformation kinetics in Fe_xAl_1-x. These studies can be useful for choosing the preparation strategy for functional alloys.
- [126] arXiv:2410.16402 (replaced) [pdf, html, other]
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Title: Universal time evolution of string order parameter in quantum critical systems with boundary invertible or non-invertible symmetry breakingComments: are welcome. 32 pages, many figures; v2: Refs addedSubjects: Strongly Correlated Electrons (cond-mat.str-el); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph); Quantum Physics (quant-ph)
The global symmetry, either invertible or non-invertible, has been extensively studied in two dimensional conformal field theories in recent years. When the theory is defined on a manifold with open boundaries, however, many interesting conformal boundary conditions will fully or partially break such global symmetry. In this work, we study the effect of symmetry-breaking boundaries or interfaces when the system is out of equilibrium. We show that the boundary or interface symmetry-breaking can be detected by the time evolution of string order parameters, which are constructed from the symmetry operators that implement the symmetry transformations. While the string order parameters are independent of time if the symmetry is preserved over the whole system, they evolve in time in a universal way if the boundary or interface breaks the symmetry. More explicitly, in the presence of boundary or interface symmetry-breaking, the string order parameters decay exponentially in time after a global quantum quench, and decay as a power-law in time after a local quantum quench. We also generalize our study to the case when the string order parameters are defined in a subsystem, which are related to the full counting statistics. It is found there are also universal features in the time evolution of string order parameters in this case. We verify our field theory results by studying the time evolution of these two different types of string order parameters in lattice models.
- [127] arXiv:2410.21757 (replaced) [pdf, html, other]
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Title: Valence Bond Crystal Ground State of the 1/9 Magnetization Plateau in the Spin-1/2 Kagome LatticeSubjects: Strongly Correlated Electrons (cond-mat.str-el)
We investigate the ground state of a spin-1/2 kagome antiferromagnet at the 1/9 magnetization plateau, focusing primarily on six types of valence bond crystal (VBC) distortions. Among six types of VBC distortions, type 1 consistently exhibits the lowest ground-state energy. Analysis of the second derivative of the energy with respect to the distortion strength $J_{\rm d}$ using exact diagonalization reveals that, as the system size approaches the thermodynamic limit, the type 1 VBC state remains stable down to $J_{\rm d} = 1$, corresponding to the undistorted kagome lattice. Perturbation theory further supports the stability of the type 1 VBC state, providing energy values that agree with exact diagonalization results within 3%. We also explore the possibility that other types of VBC distortions could become the ground state, but type 1 VBC still exhibited the lowest energy. These findings suggest that the ground state of the 1/9 plateau in the kagome lattice is the type 1 VBC state.
- [128] arXiv:2411.01031 (replaced) [pdf, html, other]
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Title: Nucleation of fracture: The first-octant evidence against classical variational phase-field modelsSubjects: Materials Science (cond-mat.mtrl-sci)
As a companion work to [1], this Note presents a series of simple formulae and explicit results that illustrate and highlight why classical variational phase-field models cannot possibly predict fracture nucleation in elastic brittle materials. The focus is on ``tension-dominated'' problems where all principal stresses are non-negative, that is, problems taking place entirely within the first octant in the space of principal stresses.
- [129] arXiv:2411.02458 (replaced) [pdf, html, other]
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Title: Tuning the lasing threshold of quantum well exciton-polaritons under a perpendicular magnetic field: a theoretical studyComments: 5 pages, 3 figuresSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Polariton lasing is a promising phenomenon with potential applications in next-generation lasers that operate without the need for population inversion. Applying a perpendicular magnetic field to a quantum well (QW) significantly alters the properties of exciton-polaritons. In this theoretical study, we investigate how the lasing threshold of QW exciton-polaritons depends on the magnetic field. By modifying the exciton's effective mass and Rabi splitting, the magnetic field induces notable changes in the relaxation kinetics, which directly affect the lasing threshold. For low-energy pumping, an increase in the magnetic field delays the lasing threshold, while for high-energy pumping, the threshold is reached at much lower pump intensities. Furthermore, increasing both the pump energy and the magnetic field enhances relaxation efficiency, leading to a substantially larger number of condensed polaritons. Our result gives insights into the modulation of exciton-polariton condensation through magnetic fields, with potential implications for the design of low-threshold polariton lasers.
- [130] arXiv:2411.09067 (replaced) [pdf, html, other]
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Title: Critical states exhibit invariance in both position and momentum spacesComments: Comments are welcomeSubjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Quantum Physics (quant-ph)
The critical states of disordered systems are intriguing subjects within the realm of condensed matter physics and complex systems. These states manifest in materials where disorder plays a significant role, and are distinguished by their multifractal structure and self-similarity. However, accurately characterizing critical states continues to pose a significant challenge. In this study, we argue that critical states exhibit a certain invariance in both position and momentum spaces, leading to their delocalization in both domains. More specifically, it is expected that typical physical quantities characterizing critical states, such as the inverse participation ratio and information entropy, should exhibit invariance in both position space and momentum space. Subsequent numerical simulations validate the correctness of this invariance, thereby establishing a robust foundation for future experimental validation of critical states.
- [131] arXiv:2411.10430 (replaced) [pdf, html, other]
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Title: Simulating the two-dimensional $t-J$ model at finite doping with neural quantum statesSubjects: Strongly Correlated Electrons (cond-mat.str-el); Disordered Systems and Neural Networks (cond-mat.dis-nn); Quantum Gases (cond-mat.quant-gas)
Simulating large, strongly interacting fermionic systems remains a major challenge for existing numerical methods. In this work, we present, for the first time, the application of neural quantum states - specifically, hidden fermion determinant states (HFDS) - to simulate the strongly interacting limit of the Fermi-Hubbard model, namely the $t-J$ model, across the entire doping regime. We demonstrate that HFDS achieve energies competitive with matrix product states (MPS) on lattices as large as $8 \times 8$ sites while using several orders of magnitude fewer parameters, suggesting the potential for efficient application to even larger system sizes. This remarkable efficiency enables us to probe low-energy physics across the full doping range, providing new insights into the competition between kinetic and magnetic interactions and the nature of emergent quasiparticles. Starting from the low-doping regime, where magnetic polarons dominate the low energy physics, we track their evolution with increasing doping through analyses of spin and polaron correlation functions. Our findings demonstrate the potential of determinant-based neural quantum states with inherent fermionic sign structure, opening the way for simulating large-scale fermionic systems at any particle filling.
- [132] arXiv:2411.12325 (replaced) [pdf, html, other]
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Title: Transport of molecules via polymerization in chemical gradientsSubjects: Soft Condensed Matter (cond-mat.soft); Statistical Mechanics (cond-mat.stat-mech)
The transport of molecules for chemical reactions is critically important in various cellular biological processes. Despite thermal diffusion being prevalent in many biochemical processes, it is unreliable for any sort of directed transport or preferential accumulation of molecules. In this paper we propose a strategy for directed motion in which the molecules are transported by active carriers via polymerization. This transport is facilitated by chemical/activity gradients which generate an effective drift of the polymers. By marginalizing out the active degrees of freedom of the system, we obtain an effective Fokker-Planck equation for the Rouse modes of such active-passive hybrid polymers. In particular, we solve for the steady state distribution of the center of mass and its mean first passage time to reach an intended destination. We focus on how the arrangement of active units within the polymer affect its steady-state and dynamic behaviour and how they can be optimized to achieve high accumulation or rapid motility.
- [133] arXiv:2411.12887 (replaced) [pdf, html, other]
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Title: Investigation of magnetic excitations and charge order in a van der Waals ferromagnet Fe$_5$GeTe$_2$V. K. Bhartiya, T. Kim, J. Li, T. P. Darlington, D. J. Rizzo, Y. Gu., S. Fan, C. Nelson, J. W. Freeland, X. Xu, D. N. Basov, J. Pelliciari, A. F. May, C. Mazzoli, V. BisogniComments: 17 pages, 3 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el)
Understanding the complex ground state of van der Waals (vdW) magnets is essential for designing new materials and devices that leverage these platforms. Here, we investigate a two-dimensional vdW ferromagnet -- Fe$_5$GeTe$_2$-- with one of the highest reported Curie temperatures, to elucidate its magnetic excitations and charge order. Using Fe $L_3 - $edge resonant inelastic x-ray scattering, we find the dual character of magnetic excitations, consisting of a coherent magnon and a continuum, similar to what is reported for its sister compound Fe$_3$GeTe$_2$. The magnon has an energy of $\approx$ 36 meV at the maximum in-plane momentum transfer ($-$0.35 r.l.u.) allowed at Fe $L_3 - $edge. A broad and non-dispersive continuum extends up to 150 meV, 50$\%$ higher energy than in Fe$_3$GeTe$_2$. Its intensity is sinusoidally modulated along the $L$ direction, with a period matching the inter-slab distance. Our findings suggest that while the unconventional dual character of magnetic excitations is generic to ternary Fe-Ge-Te vdW magnets, the correlation length of the out-of-plane magnetic interaction increases in Fe$_5$GeTe$_2$ as compared to Fe$_3$GeTe$_2$, supporting a stronger three-dimensional character for the former. Furthermore, by investigating the $\pm$(1/3, 1/3, $L$) peaks by resonant x-ray diffraction, we conclude these to have structural origin rather than charge order -- as previously reported -- and suggest doubling of the structural unit cell along the $c-$axis.
- [134] arXiv:2411.13433 (replaced) [pdf, html, other]
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Title: Symmetry breaking in two dimensions on ultra-fast time scalesComments: 7 pages, 5 figures. arXiv admin note: text overlap with arXiv:1303.6821Subjects: Soft Condensed Matter (cond-mat.soft)
Melting of two-dimensional mono-crystals is described within the celebrated Kosterlitz-Thouless-Halperin-Nelson-Young scenario (KTHNY-Theory) by the dissociation of topological defects. It describes the shielding of elasticity due to thermally activated topological defects until shear elasticity disappears. As a well defined continuous phase transition, freezing and melting should be reversible and independent of history. However, this is not the case: cooling an isotropic 2D fluid with a finite but nonzero rate does not end in mono-crystals. The symmetry can not be broken globally but only locally in the thermodynamic limit due to the critical slowing down of order parameter fluctuations. This results in finite sized domains with the same order parameter. For linear cooling rates, the domain size is described by the Kibble-Zurek mechanism, originally developed for the defect formation of the primordial Higgs-field shortly after the Big-Bang. In the present manuscript, we investigate the limit of the deepest descent quench on a colloidal monolayer and resolve the time dependence of structure formation for (local) symmetry breaking. Quenching to various target temperatures below the melting point (deep in the crystalline phase and just close to the transition), we find universal behaviour if the timescale is re-scaled properly.
- [135] arXiv:2212.03780 (replaced) [pdf, other]
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Title: Multiple Landau level filling for a mean field limit of 2D fermionsJournal-ref: Journal of Mathematical Physics volume: 65 number: 2 pages: 021902 year: 2024Subjects: Mathematical Physics (math-ph); Quantum Gases (cond-mat.quant-gas); Functional Analysis (math.FA); Quantum Physics (quant-ph)
Motivated by the quantum hall effect, we study N two dimensional interacting fermions in a large magnetic field limit. We work in a bounded domain, ensuring finite degeneracy of the Landau levels. In our regime, several levels are fully filled and inert: the density in these levels is constant. We derive a limiting mean-field and semi classical description of the physics in the last, partially filled Landau level.
- [136] arXiv:2301.05666 (replaced) [pdf, html, other]
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Title: Beyond MP2 initialization for unitary coupled cluster quantum circuitsSubjects: Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el); Chemical Physics (physics.chem-ph)
The unitary coupled cluster (UCC) ansatz is a promising tool for achieving high-precision results using the variational quantum eigensolver (VQE) algorithm in the NISQ era. However, results on quantum hardware are thus far very limited and simulations have only accessed small system sizes. We advance the state of the art of UCC simulations by utilizing an efficient sparse wavefunction circuit solver and studying systems up to 64 qubits. Here we report results obtained using this solver that demonstrate the power of the UCC ansatz and address pressing questions about optimal initial parameterizations and circuit construction, among others. Our approach enables meaningful benchmarking of the UCC ansatz, a crucial step in assessing the utility of VQE for achieving quantum advantage.
- [137] arXiv:2306.11031 (replaced) [pdf, html, other]
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Title: Chaotic turnover of rare and abundant species in a strongly interacting model communityComments: 15 pages, 7 figuresJournal-ref: PNAS 121(11) e2312822121, 2024Subjects: Populations and Evolution (q-bio.PE); Statistical Mechanics (cond-mat.stat-mech)
The composition of ecological communities varies not only between different locations but also in time. Understanding the fundamental processes that drive species towards rarity or abundance is crucial to assessing ecosystem resilience and adaptation to changing environmental conditions. In plankton communities in particular, large temporal fluctuations in species abundances have been associated with chaotic dynamics. On the other hand, microbial diversity is overwhelmingly sustained by a `rare biosphere' of species with very low abundances. We consider here the possibility that interactions within a species-rich community can relate both phenomena. We use a Lotka-Volterra model with weak immigration and strong, disordered, and mostly competitive interactions between hundreds of species to bridge single-species temporal fluctuations and abundance distribution patterns. We highlight a generic chaotic regime where a few species at a time achieve dominance, but are continuously overturned by the invasion of formerly rare species. We derive a focal-species model that captures the intermittent boom-and-bust dynamics that every species undergoes. Although species cannot be treated as effectively uncorrelated in their abundances, the community's effect on a focal species can nonetheless be described by a time-correlated noise characterized by a few effective parameters that can be estimated from time series. The model predicts a non-unitary exponent of the power-law abundance decay, which varies weakly with ecological parameters, consistent with observation in marine protist communities. The chaotic turnover regime is thus poised to capture relevant ecological features of species-rich microbial communities.
- [138] arXiv:2308.08491 (replaced) [pdf, html, other]
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Title: Conditional fluctuation theorems and entropy production for monitored quantum systems under imperfect detectionComments: 5 + 12 pages, 3 figures. The two first authors contributed equally to this work. v2: minor changes, figure added, references added. v3: 8 + 5 pages, 3 figures. New distribution of material, expanded discussions, improved presentation, references added and title modified (accepted in PRR)Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)
The thermodynamic behavior of Markovian open quantum systems can be described at the level of fluctuations by using continuous monitoring approaches. However, practical applications require assessing imperfect detection schemes, where the definition of main thermodynamic quantities becomes subtle and universal fluctuation relations are unknown. Here, we fill this gap by deriving a universal fluctuation relation that links thermodynamic entropy production and information-theoretical irreversibility along single trajectories in inefficient monitoring setups. This relation provides as a corollary an irreversibility estimator of dissipation using imperfect detection records that lower bounds the underlying entropy production at the level of visible trajectories. We illustrate our findings with a driven-dissipative two-level system following quantum jump trajectories and discuss the experimental applicability of our results for thermodynamic inference.
- [139] arXiv:2309.16658 (replaced) [pdf, html, other]
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Title: Aspects of $T\bar{T}+J\bar{T }$ deformed Schwarzian: From gravity partition function to late-time spectral form factorComments: v4: 45 pages, 9 figures, Title changed, Main text restructured, Further clarifications added, Conclusion remains unchanged, References updated, Version to appear in Physical Review DSubjects: High Energy Physics - Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el); General Relativity and Quantum Cosmology (gr-qc)
In this paper, we investigate different thermodynamic properties of $T\bar{T}+J\bar{T}$ deformed Schwarzian theory and its different gravitational perspectives. First, we compute the partition function of $U(1)$ coupled 2D-gravity with fixed chemical potential, obtained from the dimensional reduction of the four-dimensional Einstein-Maxwell theory. Then, we compute the partition function of the gravity theory which is the dual to the deformed Schwarzian living on its boundary and study the genus expansion of the one and two-point correlation function of the partition function of the theory. Subsequently, we use the one-point function to compute the "Annealed" and "Quenched" free energy in low-temperature limits and make a qualitative comparison with the undeformed theory. Then, using the two-point function, we compute the Spectral Form Factor of the deformed theory in early and late time. We find a dip and ramp structure in early and late time, respectively. We also get a plateau structure in the $\tau$-scaling limit. Last but not least, we comment on the late-time topology change to give a physical interpretation of the ramp of the Spectral Form Factor for our theory.
- [140] arXiv:2310.01338 (replaced) [pdf, html, other]
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Title: Uncovering measurement-induced entanglement via directional adaptive dynamics and incomplete informationComments: 8+13 pages, 4+9 figuresJournal-ref: Phys. Rev. A 110, L050602 (2024)Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
The rich entanglement dynamics and transitions exhibited by monitored quantum systems typically only exist in the conditional state, making observation extremely difficult. In this work we construct a general recipe for mimicking the conditional entanglement dynamics of a monitored system in a corresponding measurement-free dissipative system involving directional interactions between the original system and a set of auxiliary register modes. This mirror setup autonomously implements a measurement-feedforward dynamics that effectively retains a coarse-grained measurement record. We illustrate our ideas in a bosonic system featuring a competition between entangling measurements and local unitary dynamics, and also discuss extensions to qubit systems and truly many-body systems.
- [141] arXiv:2311.04216 (replaced) [pdf, html, other]
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Title: Directly observing replica symmetry breaking in a vector quantum-optical spin glassRonen M. Kroeze, Brendan P. Marsh, David Atri Schuller, Henry S. Hunt, Alexander N. Bourzutschky, Michael Winer, Sarang Gopalakrishnan, Jonathan Keeling, Benjamin L. LevComments: main text 6 pages and 4 figures plus references, supplement 40 pages and 26 figures plus referencesSubjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Atomic Physics (physics.atom-ph)
Spin glasses are quintessential examples of complex matter. Although much about their order remains uncertain, abstract models of them inform, e.g., the classification of combinatorial optimization problems, the magnetic ordering in metals with impurities, and artificial intelligence -- where they form a mathematical basis for neural network computing and brain modeling. We demonstrate the ability of an active quantum gas microscope to realize a spin glass of a novel driven-dissipative and vector form. By microscopically visualizing its glassy spin states, the technique allows us to directly measure replica symmetry breaking and the resulting ultrametric hierarchical structure. Ultrametricity is known to be emergent in models of evolution, protein folding, climate change, and infinite-range equilibrium spin glasses; this work shows it to be directly observable in a physically realized system.
- [142] arXiv:2401.12213 (replaced) [pdf, html, other]
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Title: Identifying gap-closings in open non-Hermitian systems by Biorthogonal PolarizationComments: typos correctedJournal-ref: J. Appl. Phys. 135, 094402 (2024)Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); High Energy Physics - Theory (hep-th); Optics (physics.optics)
We investigate gap-closings in one- and two-dimensional tight-binding models with two bands, containing non-Hermitian hopping terms, and open boundary conditions (OBCs) imposed along one direction. We compare the bulk OBC spectra with the periodic boundary condition (PBC) spectra, pointing out that they do not coincide, which is an intrinsic characteristic of non-Hermitian systems. The non-Hermiticity, thus, results in the failure of the familiar notions of bulk-boundary correspondence found for Hermitian systems. This necessitates the search for topological invariants which can characterize gap-closings in open non-Hermitian systems correctly and unambiguously. We elucidate the behaviour of two possible candidates applicable for one-dimensional slices - (1) the sum of winding numbers for the two bands defined on a generalized Brillouin zone and (2) the biorthogonal polarization (BP). While the former shows jumps/discontinuities for some of the non-Hermitian systems studied here, at points when an edge mode enters the bulk states and becomes delocalized, it does not maintain quantized values in a given topological phase. On the contrary, BP shows jumps at phase transitions, and takes the quantized value of one or zero, which corresponds to whether an actual edge mode exists or whether that mode is delocalized and absorbed within the bulk (not being an edge mode anymore).
- [143] arXiv:2402.03818 (replaced) [pdf, html, other]
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Title: Asymptotic generalization error of a single-layer graph convolutional networkJournal-ref: Proceedings of the Third Learning on Graphs Conference (LoG 2024), PMLR 269Subjects: Machine Learning (cs.LG); Disordered Systems and Neural Networks (cond-mat.dis-nn)
While graph convolutional networks show great practical promises, the theoretical understanding of their generalization properties as a function of the number of samples is still in its infancy compared to the more broadly studied case of supervised fully connected neural networks. In this article, we predict the performances of a single-layer graph convolutional network (GCN) trained on data produced by attributed stochastic block models (SBMs) in the high-dimensional limit. Previously, only ridge regression on contextual-SBM (CSBM) has been considered in Shi et al. 2022; we generalize the analysis to arbitrary convex loss and regularization for the CSBM and add the analysis for another data model, the neural-prior SBM. We also study the high signal-to-noise ratio limit, detail the convergence rates of the GCN and show that, while consistent, it does not reach the Bayes-optimal rate for any of the considered cases.
- [144] arXiv:2402.18953 (replaced) [pdf, html, other]
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Title: Noise-Robust Detection of Quantum Phase TransitionsComments: 11 pages, 10 figuresSubjects: Quantum Physics (quant-ph); Materials Science (cond-mat.mtrl-sci); Other Condensed Matter (cond-mat.other); Statistical Mechanics (cond-mat.stat-mech); Computational Physics (physics.comp-ph)
Quantum computing allows for the manipulation of highly correlated states whose properties quickly go beyond the capacity of any classical method to calculate. Thus one natural problem which could lend itself to quantum advantage is the study of ground-states of condensed matter models, and the transitions between them. However, current levels of hardware noise can require extensive application of error-mitigation techniques to achieve reliable computations. In this work, we use several IBM devices to explore a finite-size spin model with multiple `phase-like' regions characterized by distinct ground-state configurations. Using pre-optimized Variational Quantum Eigensolver (VQE) solutions, we demonstrate that in contrast to calculating the energy, where zero-noise extrapolation is required in order to obtain qualitatively accurate yet still unreliable results, calculations of the energy derivative, two-site spin correlation functions, and the fidelity susceptibility yield accurate behavior across multiple regions, even with minimal or no application of error-mitigation approaches. Taken together, these sets of observables could be used to identify level crossings in a simple, noise-robust manner which is agnostic to the method of ground state preparation. This work shows promising potential for near-term application to identifying quantum phase transitions, including avoided crossings and non-adiabatic conical intersections in electronic structure calculations.
- [145] arXiv:2403.14807 (replaced) [pdf, html, other]
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Title: Exact Hidden Markovian Dynamics in Quantum CircuitsComments: 7+11 pages, 2+1 figuresJournal-ref: Phys. Rev. Lett. 133, 170402 (2024)Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); Exactly Solvable and Integrable Systems (nlin.SI)
Characterizing nonequilibrium dynamics in quantum many-body systems is a challenging frontier of physics. In this Letter, we systematically construct solvable nonintegrable quantum circuits that exhibit exact hidden Markovian subsystem dynamics. This feature thus enables accurately calculating local observables for arbitrary evolution time. Utilizing the influence matrix method, we show that the influence of the time-evolved global system on a finite subsystem can be analytically described by sequential, time-local quantum channels acting on the subsystem with an ancilla of finite Hilbert space dimension. The realization of exact hidden Markovian property is facilitated by a solvable condition on the underlying two-site gates in the quantum circuit. We further present several concrete examples with varying local Hilbert space dimensions to demonstrate our approach.
- [146] arXiv:2404.10224 (replaced) [pdf, html, other]
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Title: Prethermalization in aperiodically driven classical spin systemsComments: Main Text (6 pages + 3 figures) + Supplementary Material (7 Pages + 11 figures)Subjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); Chaotic Dynamics (nlin.CD)
Periodically driven classical many-body systems can host a rich zoo of prethermal dynamical phases. In this work, we extend the paradigm of classical prethermalization to aperiodically driven systems. We establish the existence of a long-lived prethermal regime in spin systems subjected to random multipolar drives (RMDs). We demonstrate that the thermalization time scales as $(1/T)^{2n+2}$, where $n$ is the multipolar order and $T$ is the intrinsic time-scale associated with the drive. In the $n \rightarrow \infty$ limit, the drive becomes quasi-periodic and the thermalization time becomes exponentially long ($\sim \exp(\beta/T)$). We further establish the robustness of prethermalization by demonstrating that these thermalization time scaling laws hold for a wide range of initial state energy densities. Intriguingly, the thermalization process in these classical systems is parametrically slower than their quantum counterparts, thereby highlighting important differences between classical and quantum prethermalization. Finally, we propose a protocol to harness this classical prethermalization to realize time rondeau crystals.
- [147] arXiv:2404.14611 (replaced) [pdf, other]
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Title: Fermionic tensor network methodsQuinten Mortier, Lukas Devos, Lander Burgelman, Bram Vanhecke, Nick Bultinck, Frank Verstraete, Jutho Haegeman, Laurens VanderstraetenComments: 78 pages, 6 figuresSubjects: Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el)
We show how fermionic statistics can be naturally incorporated in tensor networks on arbitrary graphs through the use of graded Hilbert spaces. This formalism allows to use tensor network methods for fermionic lattice systems in a local way, avoiding the need of a Jordan-Wigner transformation or the explicit tracking of leg crossings by swap gates in 2D tensor networks. The graded Hilbert spaces can be readily integrated with other internal and lattice symmetries in tensor networks, and only require minor extensions to an existing tensor network software package. We review and benchmark the fermionic versions of common algorithms for matrix product states and projected entangled-pair states.
- [148] arXiv:2405.00663 (replaced) [pdf, html, other]
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Title: Quantum cryptographic protocols with dual messaging system via 2D alternate quantum walk of a genuine single-photon entangled stateComments: 13 pages (including appendix), two figures and one table, accepted for publication in Journal of Physics A: Mathematical and Theoretical as a letterJournal-ref: Journal of Physics A: Mathematical and Theoretical (2024)Subjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Cryptography and Security (cs.CR); Quantum Algebra (math.QA); Optics (physics.optics)
A single-photon entangled state (or single-particle entangled state (SPES) in general) can offer a more secure way of encoding and processing quantum information than their multi-photon (or multi-particle) counterparts. The SPES generated via a 2D alternate quantum-walk setup from initially separable states can be either 3-way or 2-way entangled. This letter shows that the generated genuine three-way and nonlocal two-way SPES can be used as cryptographic keys to securely encode two distinct messages simultaneously. We detail the message encryption-decryption steps and show the resilience of the 3-way and 2-way SPES-based cryptographic protocols against eavesdropper attacks like intercept-and-resend and man-in-the-middle. We also detail the experimental realization of these protocols using a single photon, with the three degrees of freedom being OAM, path, and polarization. We have proved that the protocols have unconditional security for quantum communication tasks. The ability to simultaneously encode two distinct messages using the generated SPES showcases the versatility and efficiency of the proposed cryptographic protocol. This capability could significantly improve the throughput of quantum communication systems.
- [149] arXiv:2405.04104 (replaced) [pdf, html, other]
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Title: A Multi-Module Silicon-On-Insulator Chip Assembly Containing Quantum Dots and Cryogenic Radio-Frequency Readout ElectronicsComments: This work has been submitted to the IEEE for possible publicationSubjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Quantum processing units will be modules of larger information processing systems containing also digital and analog electronics modules. Silicon-based quantum computing offers the enticing opportunity to manufacture all the modules using the same technology platform. Here, we present a cryogenic multi-module assembly for multiplexed readout of silicon quantum devices where all modules have been fabricated using the same fully-depleted silicon-on-insulator (FDSOI) CMOS process. The assembly is constituted by three chiplets: (i) a low-noise amplifier (LNA), (ii) a single-pole eight-throw switch (SP8T), and (iii) a silicon quantum dot (QD) array. We integrate the chiplets into modules and show respectively, (i) a peak gain over 35dB with a 3dB bandwidth from 709MHz to 827MHz and an average noise temperature of 6.2K (minimum 4.2K), (ii) an insertion loss smaller than 1.1dB and a noise temperature less than 1.1K over the 0-2GHz range, and (iii) single-electron box (SEB) charge sensors. Finally, we combine all modules into a single demonstration showing time-domain radio-frequency multiplexing of two SEBs paving the way to an all-silicon quantum computing system.
- [150] arXiv:2405.13098 (replaced) [pdf, html, other]
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Title: Do deep neural networks behave like structural glasses?Comments: 17 pages, 18 figuresSubjects: Computational Physics (physics.comp-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech)
Deep Neural Networks (DNNs) share important similarities with structural glasses. Both have many degrees of freedom, and their dynamics are governed by a high-dimensional, non-convex landscape representing either the loss or energy, respectively. Furthermore, both experience gradient descent dynamics subject to noise. In this work we investigate, by performing quantitative measurements on realistic networks trained on the MNIST and CIFAR-10 datasets, the extent to which this qualitative similarity gives rise to glass-like dynamics in neural networks. We demonstrate the existence of a Topology Trivialisation Transition as well as the previously studied under-to-overparameterised transition analogous to jamming. By training DNNs with overdamped Langevin dynamics in the resulting disordered phases, we do not observe diverging relaxation times at non-zero temperature, nor do we observe any caging effects, in contrast to glass phenomenology. However, the weight overlap function follows a power law in time, with exponent $\approx -0.5$, in agreement with the Mode-Coupling Theory of structural glasses. In addition, the DNN dynamics obey a form of time-temperature superposition. Finally, dynamic heterogeneity and ageing are observed at low temperatures. These results highlight important and surprising points of both difference and agreement between the behaviour of DNNs and structural glasses.
- [151] arXiv:2408.16466 (replaced) [pdf, html, other]
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Title: Topological zero modes and bounded modes at smooth domain walls: Exact solutions and dualitiesComments: 16 pages, 4 figures, typos fixed, some equations addedSubjects: High Energy Physics - Theory (hep-th); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Superconductivity (cond-mat.supr-con); Quantum Physics (quant-ph)
Topology describes global quantities invariant under continuous deformations, such as the number of elementary excitations at a phase boundary, without detailing specifics. Conversely, differential laws are needed to understand the physical properties of these excitations, such as their localization and spatial behavior. For instance, topology mandates the existence of solitonic zero-energy modes at the domain walls between topologically inequivalent phases in topological insulators and superconductors. However, the spatial dependence of these modes is only known in the idealized (and unrealistic) case of a sharp domain wall. Here, we find the analytical solutions of these zero-modes by assuming a smooth and exponentially-confined domain wall. This allows us to characterize the zero-modes using a few length scales: the domain wall width, the exponential decay length, and oscillation wavelength. These quantities define distinct regimes: featureless modes with "no hair" at sharp domain walls, and nonfeatureless modes at smooth domain walls, respectively, with "short hair", i.e., featureless at long distances, and "long hair", i.e., nonfeatureless at all length scales. We thus establish a universal relation between the bulk excitation gap, decay rate, and oscillation momentum of the zero modes, which quantifies the bulk-boundary correspondence in terms of experimentally measurable physical quantities. Additionally, we reveal an unexpected duality between topological zero modes and Shockley modes, unifying the understanding of topologically-protected and nontopological boundary modes. These findings shed some new light on the localization properties of edge modes in topological insulators and Majorana zero modes in topological superconductors and on the differences and similarities between topological and nontopological zero modes in these systems.
- [152] arXiv:2409.06083 (replaced) [pdf, html, other]
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Title: Information geometry approach to quantum stochastic thermodynamicsComments: 13 pages, 4 figures. Comments welcome!Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)
Recent advancements have revealed new links between information geometry and classical stochastic thermodynamics, particularly through the Fisher information (FI) with respect to time. Recognizing the non-uniqueness of the quantum Fisher metric in Hilbert space, we exploit the fact that any quantum Fisher information (QFI) can be decomposed into a metric-independent incoherent part and a metric-dependent coherent contribution. We demonstrate that the incoherent component of any QFI can be directly linked to entropic acceleration, and for GKSL dynamics with local detailed balance, to the rate of change of generalised thermodynamic forces and entropic flow, paralleling the classical results. Furthermore, we tighten a classical uncertainty relation between the geometric uncertainty of a path in state space and the time-averaged rate of information change and demonstrate that it also holds for quantum systems. We generalise a classical geometric bound on the entropy rate for far-from-equilibrium processes by incorporating a non-negative quantum contribution that arises from the geometric action due to coherent dynamics. Finally, we apply an information-geometric analysis to the recently proposed quantum-thermodynamic Mpemba effect, demonstrating this framework's ability to capture thermodynamic phenomena.
- [153] arXiv:2409.17290 (replaced) [pdf, html, other]
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Title: Temporal Bell inequalities in non-relativistic many-body physicsComments: 7 pages, 1 figureSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas)
Analyzing the spreading of information in many-body systems is crucial to understanding their quantum dynamics. At the most fundamental level, this task is accomplished by Bell inequalities, whose violation by quantum mechanics implies that information cannot always be stored locally. While Bell-like inequalities, such as the one of Clauser and Horne, envisage a situation in which two parties perform measurements on systems at different positions, one could formulate temporal inequalities, in which the two parties measure at different times. However, for causally-connected parties, these extensions are compatible with local hidden-variable theories, so that no intrinsically-quantum information spreading occurs in such temporal correlations. Here we show that a temporal Clauser-Horne inequality for two spins is violated for a nonzero time interval between the measurements if the two measured parties are connected by a spin chain. The chain constitutes a medium for the spreading of quantum information, which prevents the immediate signaling and thus the deterministic time evolution after the first measurement. Our result suggests that, as expected in a many-body setup, the Lieb-Robinson bound substitutes the speed of light as the fundamental limit for the spreading of information.
- [154] arXiv:2409.19249 (replaced) [pdf, html, other]
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Title: Enhancing the ODMR Signal of Organic Molecular QubitsComments: 11 pages, 5 figures. Some rephrasing was done for better readability and the figure texts have been enlargedSubjects: Chemical Physics (physics.chem-ph); Materials Science (cond-mat.mtrl-sci); Quantum Physics (quant-ph)
In quantum information science and sensing, electron spins are often purified into a specific polarisation through an optical-spin interface, a process known as optically-detected magnetic resonance (ODMR). Diamond-NV centres and transition metals are both excellent platforms for these so-called colour centres, while metal-free molecular analogues are also gaining popularity for their extended polarisation lifetimes, milder environmental impacts, and reduced costs. In our earlier attempt at designing such organic high-spin $\pi$-diradicals, we proposed to spin-polarise by shelving triplet $M_{S}=\pm1$ populations as singlets. This was recently verified by experiments albeit with low ODMR contrasts of $<1\%$ at temperatures above 5 K. In this work, we propose to improve the ODMR signal by moving singlet populations back into the triplet $M_{S}=0$ sublevel, designing a true carbon-based molecular analogue to the NV centre. Our proposal is based upon transition-orbital and group-theoretical analyses of beyond-nearest-neighbour spin-orbit couplings, which are further confirmed by ab initio calculations of a realistic trityl-based radical dimer. Microkinetic analyses point towards high ODMR contrasts of around $30\%$ under experimentally-feasible conditions, a stark improvement from previous works. Finally, in our quest towards ground-state optically-addressable molecular spin qubits, we exemplify how our symmetry-based design avoids Zeeman-induced singlet-triplet mixings, setting the scene for realising electron spin qubit gates.
- [155] arXiv:2410.02346 (replaced) [pdf, html, other]
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Title: Effects of grain temperature distribution on organic protostellar envelope chemistryComments: Accepted for publication in A&ASubjects: Astrophysics of Galaxies (astro-ph.GA); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Context. Dust grains in circumstellar envelopes are likely to have a spread-out temperature distribution. Aims. To investigate how trends in temperature distribution between small and large grains affect the hot corino chemistry of complex organic molecules (COMs) and warm carbon-chain chemistry (WCCC). Methods. A multi-grain multi-layer astrochemical code with an up-to-date treatment of surface chemistry was used with three grain temperature trends: grain temperature proportional to grain radius to the power -1/6 (Model M-1/6), to 0 (M0), and to 1/6 (M1/6). The cases of hot corino and WCCC chemistry were investigated, for a total of six models. The essence of these changes is for the main ice reservoir - small grains - having higher (M-1/6) or lower (M1/6) temperature than the surrounding gas. Results. The chemistry of COMs shows better agreement with observations in models M-1/6 and M1/6 than in Model M0. Model M-1/6 shows best agreement for WCCC because earlier mass-evaporation of methane ice from small grains induces the WCCC phenomenon at lower temperatures. Conclusions. Models considering several grain populations with different temperatures can more precisely reproduce circumstellar chemistry.
- [156] arXiv:2410.12733 (replaced) [pdf, html, other]
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Title: Quantum Embedding of Non-local Quantum Many-body Interactions in Prototypal Anti-tumor Vaccine Metalloprotein on Near Term Quantum Computing HardwareComments: 14 pages, 16 figuresSubjects: Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el)
The real world obeys quantum physics and quantum computing presents an alternative way to map physical problems to systems that follow the same laws. Such computation fundamentally constitutes a better way to understand the most challenging quantum problems. One such problem is the accurate simulation of highly correlated quantum systems. Due to the high dimensionality of the problem classical computers require considerable computer power to accurately predict material properties, especially when strong electron interactions are present. Still, modern day quantum hardware has many limitations and only allows for modeling of very simple systems. Here we present for the first time a quantum computer model simulation of a complex hemocyanin molecule, which is an important respiratory protein involved in various physiological processes such as oxygen transport and immune defence, and is also used as a key component in therapeutic vaccines for cancer. To better characterise the mechanism by which hemocyanin transports oxygen, variational quantum eigensolver (VQE) based on fermionic excitations and quantum embedding methods is used in the context of dynamic mean field theory to solve Anderson impurity model (AIM). Finally, it is concluded that the magnetic structure of hemocyanin is largely influenced by the many-body correction and that the computational effort for solving correlated electron systems could be substantially reduced with the introduction of quantum computing algorithms. We encourage the use of the Hamiltonian systems presented in this paper as a benchmark for testing quantum computing algorithms efficiency for chemistry applications.
- [157] arXiv:2410.13934 (replaced) [pdf, html, other]
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Title: Extractable energy from quantum superposition of current statesComments: 15 pages, 9 figuresSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas)
We explore the energy content of superpositions of current states. Specifically, we focus on the maximum energy that can be extracted from them through local unitary transformations. The figure of merit we employ is the local ergotropy. We perform a complete analysis in the whole range of the system's parameters. This way, we prove that superpositions of two current states in spatially closed spin networks are characterized by specific peaks in extractable energy, generally overcoming the ergotropy of each of the two separate current states characterized by a single winding number. The many-body state dynamics entails to ergotropy evolving in a controlled fashion. The implementation we suggest is based on a Rydberg-atom platform. Optimal transformations able to extract locally the maximum possible amount of energy are sorted out.
- [158] arXiv:2410.20662 (replaced) [pdf, html, other]
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Title: Discrete Spectrum of Interior Length and Timeshift in Two-sided Black HoleComments: 20 pages, 2 figures. v2: references addedSubjects: High Energy Physics - Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); General Relativity and Quantum Cosmology (gr-qc)
We study the spectrum of the interior length and the horizon timeshift of a two-sided black hole by constructing non-perturbative length and timeshift operators in Jackiew-Teitelboim gravity. We first construct projection operators onto the fixed length or fixed horizon timeshift subspaces using the replica trick. We calculate the densities of state for the length and the timeshift, which are found to be finite. This finiteness implies the discreteness in the spectrum of these quantities. We then construct the non-perturbative length and timeshift operators, and apply them to study the time evolution of the two-sided black hole. We find that at early time, the probability distribution of the interior length and the timeshift are sharply peaked at the classical values, while after the Heisenberg time, the distribution is completely uniform over all possible values of the length and the timeshift, indicating maximal uncertainty. In particular, the probability of having the negative timeshift states, which corresponds to the white hole probability, is $O(1)$ after the Heisenberg time.
- [159] arXiv:2411.04650 (replaced) [pdf, html, other]
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Title: Many-body nonequilibrium dynamics in a self-induced Floquet systemYuechun Jiao, Yu Zhang, Jingxu Bai, Suotang Jia, C. Stuart Adams, Zhengyang Bai, Heng Shen, Jianming ZhaoComments: 6 pages, 4 figuresSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph)
Floquet systems are periodically driven systems. In this framework, the system Hamiltonian and associated spectra of interest are modified, giving rise to new quantum phases of matter and nonequilibrium dynamics without static counterparts. Here we experimentally demonstrate a self-induced Floquet system in the interacting Rydberg gas. This originates from the photoionization of thermal Rydberg gases in a static magnetic field. Importantly, by leveraging the Rydberg electromagnetically induced transparency spectrum, we probe the nonequilibrium dynamics in the bistable regime and identify the emergence of a discrete time crystalline phase. Our work fills the experimental gap in the understanding the relation of multistability and dissipative discrete time crystalline phase. In this regard, it constitutes a highly controlled platform for exploring exotic nonequilibrium physics in dissipative interacting systems.
- [160] arXiv:2411.13190 (replaced) [pdf, html, other]
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Title: Ab-Initio Approach to Many-Body Quantum Spin DynamicsComments: 12 pages, 9 figuresSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph); Computational Physics (physics.comp-ph)
A fundamental longstanding problem in studying spin models is the efficient and accurate numerical simulation of the long-time behavior of larger systems. The exponential growth of the Hilbert space and the entanglement accumulation at long times pose major challenges for current methods. To address these issues, we employ the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) framework to simulate the many-body spin dynamics of the Heisenberg model in various settings, including the Ising and XYZ limits with different interaction ranges and random couplings. Benchmarks with analytical and exact numerical approaches show that ML-MCTDH accurately captures the time evolution of one- and two-body observables in both one- and two-dimensional lattices. A comparison of ML-MCTDH with the discrete truncated Wigner approximation (DTWA) demonstrates that our approach excels in handling anisotropic models and consistently provides better results for two-point observables in all simulation instances. Our results indicate that the multilayer structure of ML-MCTDH is a promising numerical framework for handling the dynamics of generic many-body spin systems.