Mesoscale and Nanoscale Physics
Spontaneous Breaking of the SU(3) Flavor Symmetry in a Quantum Hall Valley Nematic
G. Krizman, A. Kazakov, C.-W. Cho et al. (+10 more)
Two-dimensional
quantum materials can host original electronic phases that arise from the interplay of electronic correlations,
symmetry and
topology. In particular, the spontaneous breaking of internal
symmetry that acts simultaneously on the pseudospin and the spatial degree of freedom realizes a nematic ordering. We report evidence of a
quantum Hall valley nematic phase with an underlying SU(3) order parameter space obtained by a spontaneous polarization between the threefold degenerate valley pseudospins in Pb1-xSnxSe
quantum wells. In the presence of a Zeeman field, we demonstrate a further control of the nematic ordering with an explicit
symmetry breaking. Evidence of both spontaneous and explicit SU(3)
symmetry breaking, reminiscent of the
quark flavor paradigm, is of fundamental interest to shape the many body physics in a SU(3) system.
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All authors G. Krizman, A. Kazakov, C.-W. Cho, V. V. Volobuev, A. Majou, E. Ben Achour, T. Wojtowicz, G. Bauer, Y. Guldner, B. A. Piot, Th. Jolicoeur, G. Springholz, L.-A. de Vaulchier
Strongly Correlated Electrons
FFT-Accelerated Auxiliary Variable MCMC for Fermionic Lattice Models: A Determinant-Free Approach with $O(N\log N)$ Complexity
Deqian Kong, Shi Feng, Jianwen Xie et al. (+1 more)
We introduce a Markov Chain Monte Carlo (MCMC)
algorithm that dramatically accelerates the simulation of
quantum many-body systems, a grand challenge in computational science. State-of-the-art methods for these problems are severely limited by $O(N^3)$ computational complexity. Our method avoids this bottleneck, achieving near-linear $O(N \log N)$ scaling per sweep. Our approach samples a joint probability measure over two coupled variable sets: (1) particle trajectories of the fundamental
fermions, and (2) auxiliary variables that decouple
fermion interactions. The key innovation is a novel transition kernel for particle trajectories formulated in the
Fourier domain, revealing the transition probability as a convolution that enables massive acceleration via the Fast
Fourier Transform (FFT). The auxiliary variables admit closed-form, factorized conditional distributions, enabling efficient exact Gibbs sampling update. We validate our
algorithm on
benchmark quantum physics problems, accurately reproducing known theoretical results and matching traditional $O(N^3)$
algorithms on $32\times 32$
lattice simulations at a fraction of the wall-clock time, empirically demonstrating $N \log N$ scaling. By reformulating a long-standing physics simulation problem in machine learning
language, our work provides a powerful tool for large-scale probabilistic inference and opens avenues for physics-inspired generative models.
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All authors Deqian Kong, Shi Feng, Jianwen Xie, Ying Nian Wu
Strongly Correlated Electrons
Visualizing the Impact of Quenched Disorder on 2D Electron Wigner Solids
Zhehao Ge, Conor Smith, Zehao He et al. (+17 more)
Electron Wigner solids (WSs)1-12 provide an ideal system for understanding the competing effects of electron-electron and electron-disorder interactions, a central unsolved problem in condensed matter physics. Progress in this topic has been limited by a lack of single-defect-resolved experimental measurements as well as accurate theoretical tools to enable realistic experiment/theory comparison. Here we overcome these limitations by combining atomically-resolved scanning tunneling microscopy (STM) with neural-
quantum-state
quantum Monte Carlo (NQS-QMC) simulation of disordered 2D electron WSs to discover new disorder-induced physical regimes of correlated electron behavior. STM was used to image the electron density ($n_e$) dependent
evolution of electron WSs in gate-tunable
bilayer MoSe2 devices with varying long-range ($n_\mathrm{LR}$) and short-range ($n_\mathrm{SR}$) disorder densities. These images were compared to NQS-QMC simulations using realistic disorder maps extracted from experiment, thus allowing the roles of different disorder types to be disentangled. We identify two distinct physical regimes for disordered electron WSs that depend on $n_\mathrm{SR}$. For $n_\mathrm{SR} \lesssim n_e$ the WS behavior is dominated by long-range disorder and features extensive mixed solid-
liquid phases, a new type of local re-entrant melting/crystallization, and prominent Friedel oscillations. In contrast, when $n_\mathrm{SR} \gg n_e$ these features are suppressed and a more robust amorphous WS phase emerges that persists to higher ne, highlighting the importance of short-range disorder in this regime. Our work establishes a powerful framework for studying disordered
quantum solids via a combined experimental-theoretical approach.
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All authors Zhehao Ge, Conor Smith, Zehao He, Yubo Yang, Qize Li, Ha-Leem Kim, Ziyu Xiang, Jianghan Xiao, Wenjie Zhou, Salman Kahn, Aining Hu, Melike Erdi, Rounak Banerjee, Takashi Taniguchi, Kenji Watanabe, Seth Ariel Tongay, Miguel A. Morales, Shiwei Zhang, Feng Wang, Michael F. Crommie
Strongly Correlated Electrons
Evidence for easy-plane XY ferromagnetism in heavy-fermion quantum-critical CeRh6Ge4
Riku Yamamoto, Sejun Park, Zachary W. Riedel et al. (+6 more)
We report $^{73}$Ge
nuclear quadrupole resonance (NQR) and
magnetic resonance (NMR) spectroscopy in the heavy-
fermion quantum-critical ferromagnet CeRh$_6$Ge$_4$. NQR and NMR spectral measurements at the two non-equivalent Ge sites reveal electric field gradient tensors and the directions of their principal axes relative to the hexagonal basal plane. The
spin-
lattice relaxation rate $1/T_1$ experiments reveal a clear critical slowing down approaching the
ferromagnetic transition. $1/T_1$ in the paramagnetic state is found to be predominantly caused by fluctuating 4$f$-local moments. The Knight shift shows Curie-Weiss behavior at high temperature and a deviation from this below $T^\ast$ $\approx$ 25 K possibly due to a mixture of crystalline electric field effects and Kondo screening. Order-parameter-like behavior of hyperfine fields at the Ge sites and
ferromagnetic signal enhancement are observed in Zeeman-perturbed NQR, with uniform
ferromagnetic order and a small ordered moment of $\approx$ 0.26 $\mu_B$/Ce confined within the $ab$-plane. The ordered moment shows a notable in-plane
magnetic stiffness against out-of-plane radiofrequency fields and has an (XY-type) in-plane isotropic nature. Our results reveal a strong easy-plane anisotropy of 4$f$-electron moment and suggest an involved interplay of hybridization and local moment physics in this
quantum critical heavy-
fermion ferromagnet.
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All authors Riku Yamamoto, Sejun Park, Zachary W. Riedel, Phurba Sherpa, Joe D. Thompson, Filip Ronning, Eric D. Bauer, Adam P. Dioguardi, Michihiro Hirata
Materials Science
The Comparison of Colloidal PbS QD Photoconductors and Hybrid Phototransistors
Gökhan Kara, Lorenzo J. A. Ferraresi, Dmitry N. Dirin et al. (+4 more)
The simplicity in the fabrication of photoconductors makes them a valuable choice to investigate optoelectronic properties of colloidal
quantum dot (cQD) films. Lateral photoconductors generally require a large size, in the mm2, and are limited in operation speed due to the presence of trapping sites. In contrast, hybrid phototransistors are fabricated in the um2 scale and benefit from such trapping sites, allowing the measurement of low light levels in the nW/cm2. The question, however, arises whether high responsivity values are required for the detection of low light levels or the compatible detectivity of photoconductors is sufficient. Here, we directly compare photoconductors and hybrid phototransistors with an identical EDT-treated PbS cQD film. We highlight that a comparable D* is not enough for the purpose of measuring low light levels, as the resulting photocurrents need to be readily accessible. Furthermore, we also showcase temperature-activated photocurrent dynamics resulting in a negative photocurrent (NPC) effect. This NPC simultaneously improves the frequency bandwidth and photocurrent, enabling operation speeds up to 100 kHz.
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All authors Gökhan Kara, Lorenzo J. A. Ferraresi, Dmitry N. Dirin, Roman Furrer, Maksym V. Kovalenko, Michel Calame, Ivan Shorubalko
Statistical Mechanics · Cross-listed from quant-ph
Open Quantum Dynamics Theory for Coulomb Potentials: Hierarchical Equations of Motion for Atomic Orbitals (AO-HEOM)
Yankai Zhang and Yoshitaka Tanimura
We investigate the
quantum dynamics of Coulomb potential systems in thermal baths. We study these systems within the framework of open
quantum dynamics theory, focusing on preserving the rotational
symmetry of the entire system, including the baths. Thus, we employ a three-dimensional rotationally invariant system-bath (3D-RISB) model to derive numerically “exact” hierarchical equations of motion for atomic orbitals (AO-HEOM) that enable a non-perturbative and non-Markovian treatment of system-bath interactions at finite temperatures. To assess the formalism, we calculated the linear absorption spectrum of an atomic system under isotropic thermal environment, with systematic variation of system-bath coupling strength and temperature.
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Materials Science
Microscopic Intricacies of Self-Healing in Halide Perovskite-Charge Transport Layer Heterostructures
Tejmani Behera, Boris Louis, Lukas Paesen et al. (+7 more)
The stability and performance of halide perovskite photovoltaic devices are critically limited by progressive defect generation and associated local non-radiative losses during operation. Self-healing of defects provides a promising pathway to prolong device functionality, yet the underlying microscopic mechanisms remain poorly understood, particularly the role of interfacial chemistry on trap dynamics and healing kinetics. Here, we elucidate self-healing and defect
evolution in triple-cation mixed halide (TCMH) perovskite films and their device-relevant charge transport layer
heterostructures subjected to photo-induced damage. Using correlation clustering imaging (CLIM), our recently developed local functional imaging tool, we map spatiotemporal photoluminescence heterogeneity to track defect dynamics in pristine and
heterostructure films. The defect healing follows bi-phasic kinetics, with an initial electronic relaxation (tens of minutes) and a subsequent slower phase (~ hours) associated to ionic and
lattice rearrangement. Most importantly, our results demonstrate that the chemical nature of charge-transport layers modulates trap activity, healing kinetics, and halide redistribution, with
heterostructures exhibiting faster recovery than pristine films, a boon for device resilience. These findings provide new insights into the dynamic interaction between defects, interfaces, and ion migration, and establish a framework for rational design of durable, next-generation perovskite optoelectronic devices.
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All authors Tejmani Behera, Boris Louis, Lukas Paesen, Roel Vanden Brande, Koki Asano, Martin Vacha, Maarten Roeffaers, Elke Debroye, Johan Hofkens, Sudipta Setha
Materials Science
Orbitally-Resolved Mechanical Properties of Solids from Maximally Localized Wannier Functions
Ethan T. Ritz, Guru Khalsa, Hsin-Yu Ko et al. (+3 more)
We present a technique for partitioning the total energy from a semi-local density functional theory calculation into contributions from individual electronic states in a localized Wannier basis. We use our technique to reveal the key role played by the $s$ and $p$ orbitals of the apical oxygen atoms in a curious elastic anomaly exhibited by ferroelectric PbTiO$_3$ under applied stress, which has so far gone unexplained. Our technique enables new insights into the chemical origins of the mechanical properties of materials, or any property given by an energy derivative.
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All authors Ethan T. Ritz, Guru Khalsa, Hsin-Yu Ko, Ju-an Zhang, Robert A. DiStasio Jr., Nicole A. Benedek
Materials Science
Thermal transport in GaN/AlN HEMTs on 4H-SiC: Role of layer thickness and hetero-interfaces
Dat Q. Tran, Minho Kim, Okhyun Nam et al. (+2 more)
Thermal transport in high-electron-mobility-transistor (HEMT) structures grown on 4H-SiC substrates by metalorganic-vapour-phase epitaxy (MOCVD) is systematically investigated. The thermal conductivity of the GaN channel and AlN buffer layers is measured by thermoreflectance (TTR). A pronounced thickness dependence of thermal conductivity as a result of
phonon-boundary scattering is observed at low temperatures, while this effect becomes significantly weaker at elevated temperatures. The thermal boundary resistance (TBR) at the AlN/4H-SiC and GaN/AlN interfaces is also examined, showing a substantial reduction and eventual saturation with increasing temperature, indicating elastic
phonon transport as the dominant mechanism. Reliable simulations of the temperature profile across the structures based on the measured thermal metrics highlight the critical role of TBR in thin-channel device and the advantage of thicker channel and buffer layers for efficient heat dissipation in the HEMTs.
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All authors Dat Q. Tran, Minho Kim, Okhyun Nam, Vanya Darakchieva, Plamen P. Paskov
Materials Science
Spectroscopy of Sm$^{3+}$ Ions in the C$_{\rm s}$ Symmetry Centres of Hydrothermally Prepared K$_2$YF$_5$ Microcrystals
Pakwan Chanprakhon, Michael F. Reid and and Jon-Paul R. Wells
We report on the synthesis and spectroscopic characterization of Sm$^{3+}$-doped K$_2$YF$_5$ microparticles. The particles were synthesized via the hydrothermal technique, yielding a particle size of approximately 20 $\mu$m in length. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses confirmed their orthorhombic
crystal structure. A combination of absorption and
laser excited fluorescence performed on samples cooled to 10~K, allow for the determination of {56} experimental
crystal-field levels. A parametrised
crystal-field analysis for Sm$^{3+}$ in the C$_{\rm s}$ point group
symmetry centres of K$_2$YF$_5$ yields good approximation to the data.
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Materials Science
Bond-resolved STM with density-based methods
Emiliano Ventura-Macias, Jose Martinez-Castro, Guillermo Haas et al. (+7 more)
Bond-resolved scanning tunneling microscopy (BRSTM) provides intramolecular contrast with CO-functionalized tips, but its interpretation requires a description of both probe relaxation and orbital-dependent tunneling. We introduce a simulation framework that combines the Full-Density-Based Model (FDBM) for CO-tip relaxation with Chen's derivative rules applied directly to real-space density-functional-theory (DFT) wave functions. We test the method against a series of constant-height BRSTM images of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on Ag(111), acquired in 10~pm tip-height increments, and published data for 1,5,9-trioxo-13-azatriangulene (TOAT) on Cu(111). The simulations reproduce the principal intramolecular contrast features and their
evolution with tip height. The comparison identifies distinct roles for the substrate: it modifies the partially occupied molecular states and probe–sample forces in PTCDA/Ag(111), while its influence on the TOAT/Cu(111) contrast remains relevant even without substantial changes in molecular-orbital occupation. Our framework thus provides a practical and accurate route to interpreting BRSTM images that incorporates, from a single DFT calculation, the separate contributions of electronic structure and CO-tip relaxation.
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All authors Emiliano Ventura-Macias, Jose Martinez-Castro, Guillermo Haas, Jara Trujillo-Mulero, Pablo Pou, Taner Esat, Markus Ternes, Ruslan Temirov, F. Stefan Tautz, Ruben Perez
Materials Science · Cross-listed from physics.chem-ph
Enhancing Diffusion-Based Sampling with Molecular Collective Variables
Juno Nam, Bálint Máté, Artur P. Toshev et al. (+6 more)
Diffusion-based samplers learn to sample complex, high-dimensional distributions using energies or log densities alone, without training data. Yet, they remain impractical for molecular sampling because they are often slower than molecular dynamics and miss thermodynamically relevant modes. Inspired by enhanced sampling, we encourage exploration by introducing a sequential bias along bespoke, information-rich, low-dimensional projections of atomic coordinates known as collective variables (CVs). We introduce a repulsive potential centered on the CVs from recent samples, which pushes future samples towards novel CV regions and effectively increases the temperature in the projected space. Our resulting method improves efficiency, mode discovery, enables the estimation of free energy differences, and retains independent sampling from the approximate Boltzmann distribution via reweighting by the bias. On standard peptide conformational sampling
benchmarks, the method recovers diverse conformational states and accurate free energy profiles. We are the first to demonstrate reactive sampling using a
diffusion-based sampler, capturing bond breaking and formation with universal interatomic potentials at near-first-principles accuracy. The approach resolves reactive energy landscapes at a fraction of the wall-clock time of standard sampling methods, advancing
diffusion-based sampling towards practical use in molecular sciences.
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All authors Juno Nam, Bálint Máté, Artur P. Toshev, Manasa Kaniselvan, Rafael Gómez-Bombarelli, Ricky T. Q. Chen, Brandon Wood, Guan-Horng Liu, Benjamin Kurt Miller
Superconductivity
Low-field all-optical detection of superconductivity using NV nanodiamonds
Omkar Dhungel, Saravanan Sengottuvel, Mariusz Mrozek et al. (+5 more)
Nitrogen-vacancy centers in nanodiamond offer a microwave-free, noninvasive platform for probing
superconductors via near zero-field cross-relaxation magnetometry. We demonstrate this by depositing nanodiamonds on YBCO thin films to measure critical parameters: transition temperature and penetration field. This method leverages nanodiamond fluorescence modulation as a result of
magnetic field variation with 1mT amplitude to observe the Meissner effect and field scans to measure the penetration field. The approach is minimally invasive and can be applied to superconducting samples with rough surfaces, facilitating the study of flux
vortices and critical phenomena in complex geometries.
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All authors Omkar Dhungel, Saravanan Sengottuvel, Mariusz Mrozek, Till Lenz, Nir Bar-Gill, Adam M. Wojciechowski, Arne Wickenbrock, Dmitry Budker
Soft Condensed Matter
Modelling of magnetic vortex microdisc dynamics under varying magnetic field in biological viscoelastic environments
Andrea Visonà, Robert Morel, Hélène Joisten et al. (+2 more)
Magnetically driven microparticles provide a versatile platform for probing and manipulating biological systems, yet the physical framework governing their actuation in complex environments remains only partially explored. Within the field of cellular magneto-mechanical stimulation,
vortex microdiscs have emerged as particularly promising candidates for developing novel therapeutic approaches. Here, we introduce a simplified two-dimensional model describing the magneto-mechanical response of such particles embedded in viscoelastic media under varying
magnetic fields. Using a Maxwell description of the medium combined with simplified elasticity assumptions, we derive analytical expressions and support them with numerical simulations of particle motion under both oscillating and rotating
magnetic fields. Our results show that rotating fields typically induce oscillatory dynamics and that the transition to asynchronous motion occurs at a critical frequency determined by viscosity and stiffness. The amplitude and phase of this motion is governed by the competition between
magnetic and viscoelastic contributions, with particle motion being strongly impaired when the latter dominate. Energy-based considerations further demonstrate that, within the frequency range explored of few tens of Hertz, no heat is generated – distinguishing this approach from
magnetic hyperthermia – while the elastic energy transferred to the surrounding medium is, in principle, sufficient to perturb major cellular processes. This work provides a simple framework to anticipate the first-order influence of rheological properties on magnetically driven microdisc dynamics, thereby enabling a better understanding of their impact in
cells or extracellular materials and bridging the gap between experimental observations and theoretical modelling.
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All authors Andrea Visonà, Robert Morel, Hélène Joisten, Bernard Dieny, Alice Nicolas
Mesoscale and Nanoscale Physics
Neuromorphic heat transport effects in a molecular junction
Renai Chen and Galen T. Craven
Understanding energy transport at the nanoscale is an open and fundamental challenge in the molecular sciences with direct implications for the design of new electronics, computing devices, and materials. While nanoscale energy transport under steady-state conditions has been studied extensively, there is much less known about energy transport under time-dependent driving forces, particularly in the far-from-
equilibrium regime. In this work, we use nonequilibrium molecular dynamics simulations and
stochastic thermodynamics to investigate energy transport in a well-studied nanoscale system, a molecular junction, subjected to a time-periodic temperature gradient. The primary observation is that molecular junctions can exhibit heat transport hysteresis, a phenomenon in which the heat flux through a system depends not only on the instantaneous value of a time-dependent temperature bias but also on the temporal history of that bias. The presented findings illustrate that molecular junctions can exhibit the specific
memory effect, heat transport hysteresis, that is essential for the design of thermal neuromorphic computers. This work elucidates a potential pathway toward the realization of such devices.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Dipole-quadrupole model and multipole analysis of resonant membrane metasurfaces
Izzatjon Allayarov, Andrey B. Evlyukhin and Antonio Calà Lesina
Membrane-metasurfaces, formed by periodic arrangements of holes in a dielectric layer, are gaining
attention for their easier manufacturing via subtractive techniques, unnecessity of substrates, and access to resonant near-fields. Despite their practical relevance, their theoretical description remains elusive. Here, we present a semi-analytical dipole-quadrupole model for the multipole analysis of numerically-obtained reflection and transmission spectra in metasurfaces excited at arbitrary angles. Dipole models are generally sufficient to study traditional metasurfaces made of solid nanostructures. However, the inclusion of electric and
magnetic quadrupoles is necessary to study membrane-metasurfaces, which offer an ideal platform to showcase our method. We demonstrate the importance of choosing the optimal position of a symmetric membrane-metasurface's unit
cell to ensure the sufficiency of the dipole-quadrupole approximation. We show that our formalism can explain complex phenomena arising from inter-multipole interference, including
lattice anapole and generalized Kerker effects, Fano resonances, and quasi-bound states in the continuum. We also present the applicability of the method to membrane-metasurfaces with non-centrosymmetric unit
cells (e.g., conical holes and surface voids). By enabling a deeper insight into the coupling mechanisms leading to the formation of local and collective resonances, our method expands the electromagnetics toolbox to study, understand, and design conventional and membrane-metasurfaces.
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Mesoscale and Nanoscale Physics
Topological Robustness of Anyon Tunneling at $\nu = 1/3$
Adithya Suresh, Ramon Guerrero-Suarez, Tanmay Maiti et al. (+4 more)
The scaling exponent $g$ of the quasiparticle propagator for incompressible fractional
quantum Hall states in the Laughlin sequence is expected to be robust against perturbations that do not close the gap. Here we probe the topological robustness of the
chiral Luttinger
liquid at the boundary of the $\nu=1/3$ state by measuring the tunneling conductance between counterpropagating edge modes as a function of
quantum point contact transmission. We demonstrate that for transmission $t\geq 0.7$ the tunneling conductance is well-described by the first two terms of a perturbative series expansion corresponding to $g=1/3$. We further demonstrate that the measured scaling exponent is robustly pinned to $g=1/3$ across the plateau, only deviating as the bulk state becomes compressible. Finally we examine the impact of weak disorder on the scaling exponent, finding it insensitive. These measurements firmly establish the topological robustness of anyon tunneling at $\nu=1/3$ and substantiate the
chiral Luttinger
liquid description of the edge mode.
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All authors Adithya Suresh, Ramon Guerrero-Suarez, Tanmay Maiti, Shuang Liang, Geoffrey Gardner, Claudio Chamon, Michael Manfra
Disordered Systems and Neural Networks
Non-perturbatively slow spread of quantum correlations in non-resonant systems
Ben T. McDonough, Marius Lemm and Andrew Lucas
Strong disorder often has drastic consequences for
quantum dynamics. This is best illustrated by the phenomenon of Anderson localization in non-interacting systems, where destructive
quantum wave interference leads to the complete absence of particle and information transport over macroscopic distances. In this work, we investigate the extent to which strong disorder leads to provably slow dynamics in many-body
quantum lattice models. We show that in any spatial dimension, strong disorder leads to a non-perturbatively small velocity for ballistic information transport under
unitary quantum dynamics, almost surely in the thermodynamic limit, in every many-body state. In these models, we also prove the existence of a "prethermal many-body localized regime", where
entanglement spreads logarithmically slowly, up to non-perturbatively long time scales. More generally, these conclusions hold for all models corresponding to
quantum perturbations to a classical
Hamiltonian obeying a simple non-resonant condition. Deterministic non-resonant models are found, including
spin systems in strong incommensurate
lattice potentials. Consequently,
quantum dynamics in non-resonant potentials is asymptotically easier to simulate on both classical or
quantum computers, compared to a generic many-body system.
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Soft Condensed Matter
Memories of amplitude and direction coexist and compete in non-Brownian suspensions
Surendra Padamata and Nathan C. Keim
Steadily shearing a non-Brownian suspension forms a
memory of direction, while shearing back and forth forms a
memory of amplitude. Each
memory is evident in the systems response to further shear, exemplifying its strong history-dependence. By combining the steady and oscillatory experiments, we show these
memories are distinct but intersecting aspects of the same non-
equilibrium physics: they can coexist, yet a specific amplitude suppresses directional
memory and makes the system symmetric. Combined with prior results from disordered solids, our work presents a simple motif for limited
memory capacity in non-
equilibrium matter.
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Soft Condensed Matter
Universal scaling of shear thickening suspensions under acoustic perturbation
Anna R. Barth, Navneet Singh, Stephen J. Thornton et al. (+7 more)
Tuning shear thickening behavior is a longstanding problem in the field of dense suspensions. Acoustic perturbations offer a convenient way to control shear thickening in real time, opening the door to a new class of smart materials. However, complete control over shear thickening requires a quantitative description for how suspension viscosity varies under acoustic perturbation. Here, we achieve this goal by experimentally probing suspensions with acoustic perturbations and incorporating their effect on the suspension viscosity into a universal scaling framework where the viscosity is described by a scaling function, which captures a crossover from the frictionless jamming critical point to a frictional shear jamming critical point. Our analysis reveals that the effect of acoustic perturbations may be explained by the introduction of an effective interparticle repulsion whose magnitude is roughly equal to the acoustic energy density. Furthermore, we demonstrate how this scaling framework may be leveraged to produce explicit predictions for the viscosity of a dense suspension under acoustic perturbation. Our results demonstrate the utility of the scaling framework for experimentally manipulating shear thickening systems.
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All authors Anna R. Barth, Navneet Singh, Stephen J. Thornton, Pranav Kakhandiki, Edward Y.X. Ong, Meera Ramaswamy, Abhishek M. Shetty, Bulbul Chakraborty, James P. Sethna, Itai Cohen
Statistical Mechanics · Cross-listed from quant-ph
Secret communication games and a hierarchy of quasiparticle statistics in 3 + 1D topological phases
Zhiyuan Wang
We show that a family of secret communication challenge games naturally define a hierarchy of emergent quasiparticle statistics in three-dimensional (3D) topological phases. The winning strategies exploit a special class of the recently proposed $R$-paraparticles to allow nonlocal secret communication between the two participating players. We first give a high-level, axiomatic description of emergent $R$-paraparticles, and show that any physical system hosting such particles admits a winning strategy. We then analyze the games using the categorical description of topological phases (where point-like excitations in 3D are described by symmetric fusion categories), and show that only $R$-paraparticles can win the 3D challenge in a noise-robust way, and the winning strategy is essentially unique. This analysis associates emergent $R$-paraparticles to deconfined gauge theories based on an exotic class of finite groups. Thus, even though this special class of $R$-paraparticles are
fermions or
bosons under the categorical classification, their exchange statistics can still have nontrivial physical consequences in the presence of appropriate defects, and the $R$-paraparticle
language offers a more convenient description of the winning strategies. Finally, while a subclass of non-Abelian anyons can win the game in 2D, we introduce twisted variants that exclude anyons, thereby singling out $R$-paraparticles in 2D as well. Our results establish the secret communication challenge as a versatile diagnostic for both identifying and classifying exotic exchange statistics in topological
quantum matter.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Nisarga Paul
Variational wavefunctions offer a practical route around the exponential complexity of many-body
Hilbert spaces, but their expressive power is often sharply constrained.
Matrix product states, for instance, are efficient but limited to area law entangled states. Neural
quantum states (NQS) are widely believed to overcome such limitations, yet little is known about their fundamental constraints. Here we prove that feed-forward neural
quantum states acting on $n$
spins with $k$ scalar nonlinearities, under certain analyticity assumptions, obey a bound on
entanglement entropy for any subregion: $S \leq c k\log n$, for a constant $c$. This establishes an NQS analog of the area law constraint for
matrix product states and rules out volume law
entanglement for NQS with $O(1)$ nonlinearities. We demonstrate analytically and numerically that the scaling with $n$ is tight for a wide variety of NQS. Our work establishes a fundamental constraint on NQS that applies broadly across different network designs, while reinforcing their substantial expressive power.
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Statistical Mechanics
Adjoint ferromagnets
Joaquín López-Suárez, Alexios P. Polychronakos and Konstantinos Sfetsos
We derive the phase structure and thermodynamics of ferromagnets consisting of elementary magnets carrying the adjoint representation of $SU(N)$ and coupled through two-body quadratic interactions. Such systems have a continuous $SU(N)$
symmetry as well as a discrete conjugation
symmetry. We uncover a rich spectrum of phases and transitions, involving a paramagnetic and two distinct
ferromagnetic phases that can coexist as stable and metastable states in different combinations over a range of temperatures. The
ferromagnetic phases break $SU(N)$ invariance in various channels, leading to spontaneous magnetization. Interestingly, the conjugation
symmetry also breaks over a range of temperatures and group ranks $N$, providing a realization of a spontaneously broken discrete
symmetry.
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Materials Science · Cross-listed from physics.class-ph
Advanced creep modelling for polymers: A variable-order fractional calculus approach
José Geraldo Telles Ribeiro and Americo Cunha Jr
Polymer-based plastics exhibit time-dependent deformation under constant stress, known as creep, which can lead to rupture or static fatigue. A common misconception is that materials under tolerable static loads remain unaffected over time. Accurate long-term deformation predictions require experimental creep data, but conventional models based on simple rheological elements like springs and dampers often fall short, lacking the flexibility to capture the power-law behaviour intrinsic to creep processes. The springpot, a fractional calculus-based element, has been used to provide a power-law relationship; however, its fixed-order nature limits its accuracy, particularly when the deformation rate evolves over time. This article introduces a variable-order (VO) springpot model that dynamically adapts to the evolving viscoelastic properties of polymeric materials during creep, capturing changes between glassy, transition and rubbery phases. Model parameters are calibrated using a robust procedure for model identification based on the cross-
entropy (CE) method, resulting in physically consistent and accurate predictions. This advanced modelling framework not only overcomes the limitations of the fixed-order models but also establishes a foundation for applying VO mechanics to other viscoelastic materials, providing a valuable tool for predicting long-term material performance in structural applications.
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