Mesoscale and Nanoscale Physics
Vanadium doping induced valley asymmetries in WS$_2$ monolayers
Frederico B. Sousa, Boyang Zheng, Elizabeth Grace Houser et al. (+10 more)
Transition metal dichalcogenide (TMD) monolayers offer an innovative platform for encoding and manipulating information through the valley degree of freedom. While unique valley-related physical phenomena have been reported so far, practical applications still require advanced control over the valley polarization efficiency and the valley Zeeman effect. Recently, the introduction of
spin-polarized metal atoms as substitutional defects was reported to break the time-reversal
symmetry in TMD monolayers, consequently inducing a room-temperature ferromagnetic ordering and enhancing the valley-dependent optical responses. Here, we report valley asymmetries for vanadium-doped WS$_2$ monolayers. With a given
magnetic polarization, one valley exhibits larger Zeeman slope and degree of circular polarization than the other valley. Additionally, the overall degree of circular polarization in the doped samples is approximately twice that of the pristine WS$_2$ monolayer. Density functional theory calculations in the doped structure show that different energy shifts in conduction band edges due to
spin-dependent hybridization lead to different
exciton energies between valleys, which is consistent with the experimental observations. Our results pave the way for valleytronic technologies based on defect-engineered two-dimensional materials.
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All authors Frederico B. Sousa, Boyang Zheng, Elizabeth Grace Houser, Paulo E. Faria Junior, Zhuohang Yu, Alessandra Ames, Gabriel A. D. Souza, Mingzu Liu, Gilmar Eugenio Marques, Leandro M. Malard, Mauricio Terrones, Vincent H. Crespi, Marcio D. Teodoro
Mesoscale and Nanoscale Physics · Cross-listed from physics.app-ph
Boundary-condition identification from a scale-invariant frequency ratio in shear-deformable and nonlocal beams and plates
Ak{\i}n Oktav
The ratio of a structure's first two natural frequencies depends on its boundary conditions but not on its size, material density, or absolute stiffness, which multiply every frequency equally and cancel in the quotient. We use this to identify the boundary conditions of a small-scale beam or plate from two ratio measurements, without knowing its exact dimensions or material. The paper first establishes how the ratio $r=\omega_2/\omega_1$, and the fractional shift $\Delta r$ it undergoes when a boundary condition changes, respond to the two effects that matter at small scale: transverse shear deformation, through Timoshenko beam and Mindlin plate theory, and small-scale elasticity, through Eringen's nonlocal Timoshenko model. Using a locking-free Rayleigh-Ritz beam solver and a finite-element Mindlin plate solver, each checked against
benchmarks, we find an asymmetry. The absolute ratio moves appreciably with thickness, by 12 to 14 per cent over the shear-deformable range, and with orthotropy, by 6 to 9 per cent, but only weakly with nonlocality; the shift $\Delta r$, by contrast, varies by less than 0.2 per cent over the full nonlocal range and by a few per cent under thickness change. Because $\Delta r$ is largely independent of these details, a measured shift identifies which boundary-condition transition a deliberate change of support has produced, with a resolution we quantify and verify against molecular-dynamics data. Two spring continua then extend the method to estimating support compliance, with the non-uniqueness of the tip-support case stated explicitly. The method needs no value of the small-scale parameter or the material constants.
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Materials Science
Compressive Splitting in Brittle Solids: The Inverse of Wrinkling in Sheets
Maryam Khodadad, Francois Barthelat, John D. Clayton et al. (+2 more)
Axial splitting is the dominant failure mode of brittle solids under compression, yet its mechanical origin remains unclear. We show that clamped loading platens suppress lateral Poisson expansion, generating boundary-induced tensile stresses at the specimen interior – the compressive analog of wrinkling in stretched sheets. This mechanism provides a predictive strength law, relating axial splitting to tensile strength, geometry, and confinement pressure. This is validated against diverse materials ranging from rocks to ceramics, establishing axial splitting as a geometry-controlled elastic process rather than a
stochastic flaw problem.
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All authors Maryam Khodadad, Francois Barthelat, John D. Clayton, George Gazonas, Kaushik Dayal
Statistical Mechanics
Intermittency in Wind-Driven Fires
Laurent Hébert-Dufresne, Aanjaneya Kumar and S. Redner
We construct a wind-driven forest-fire model in one dimension in which a fire can jump gaps between trees to ignite disjoint downwind forests. The size of a gap that a fire can jump depends on the fire intensity, which increases as the fire propagates through trees and diminishes as the fire jumps gaps. Trees grow on empty sites at rate $r$ and lightning strikes each site with rate $f$. When $f\ll r/L$, where $L$ is the system length, lightning is sufficiently rare that quasi-deterministic dynamics arises where all trees are consumed when a lightning-induced fire occurs. For $f\gg L^{-\mu}$ with $\mu\approx 0.8$, lightning is sufficiently frequent that a steady state is reached, but with unexpected behaviors for the forest- and gap-size distributions. Intermittency arises in between these regimes, with coexisting temporal domains of deterministic and chaotic dynamics.
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Strongly Correlated Electrons
Approaching the Inverse Neutron Scattering Problem with Neural Networks
Jingyi Luo, Fletcher Williams, Ang-Kun Wu et al. (+3 more)
Determining the microscopic
Hamiltonian of a
quantum magnet from inelastic
neutron scattering measurements remains a central challenge in condensed matter physics. While the dynamical
spin structure factor contains, in principle, sufficient information about the underlying interactions, extracting
Hamiltonian parameters from experimental spectra constitutes a highly nontrivial inverse problem due to the large parameter space and the presence of experimental noise. Here we demonstrate that neural networks can efficiently solve this inverse problem for a broad class of
quantum magnets. As a
benchmark, we consider an eight-parameter family of honeycomb
lattice Heisenberg
spin models in the fully polarized phase, where the dynamical
spin structure factor can be computed exactly within linear
spin-wave theory. Using a large synthetic
dataset of
neutron scattering spectra, we train neural networks to infer the underlying
Hamiltonian parameters directly from the dynamical response. We compare the performance of three different architectures—fully connected neural networks (FCNNs), one-dimensional convolutional neural networks (CNN1Ds), and two-dimensional convolutional neural networks (CNN2Ds)—and find that all achieve high predictive accuracy. Remarkably, the trained models remain robust in the presence of substantial experimental uncertainty, reliably recovering the
Hamiltonian parameters even when the input spectra are contaminated by random noise with amplitudes reaching $10\%$ of the signal intensity. Our results establish machine learning as a powerful framework for quantitative
Hamiltonian reconstruction from
neutron scattering data and provide a practical route toward automated characterization of
quantum magnetic materials.
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All authors Jingyi Luo, Fletcher Williams, Ang-Kun Wu, David Dahlbom, Cristian D. Batista, Hao Zhang
Soft Condensed Matter
Two-Stage Ordering Kinetics in Binary Mixtures of Ellipsoidal Particles
Parameshwaran A, Sanjay Puri and Bhaskar Sen Gupta
We investigate the nonequilibrium phase-ordering kinetics of a binary mixture of uniaxial ellipsoidal particles interacting via the anisotropic Gay-Berne potential using large-scale molecular dynamics simulations. Following a temperature quench from the isotropic and homogeneous phase into the coexistence region, the system exhibits two distinct ordering processes occurring on different time scales. At first, rapid orientational ordering leads to the formation and coarsening of nematic domains, characterized by dynamical scaling, generalized Porod-law behavior, and a growth law $\ell(t) \sim t^{1/2}$ consistent with nonconserved order-parameter dynamics. Later, the system undergoes binary phase separation driven by compositional fluctuations. This compositional ordering process shows a transition from diffusive growth $\ell(t) \sim t^{1/3}$ to hydrodynamic regimes, with finite-size scaling analysis indicating asymptotic viscous growth $\ell(t) \sim t$. Despite the presence of global orientational order, the phase-separation kinetics remains effectively isotropic. These results demonstrate a clear separation between orientational and compositional ordering dynamics, governed by distinct conservation laws, and provide a unified framework for understanding phase ordering in anisotropic particle systems.
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Statistical Mechanics
Diffusion with stochastic resetting in the presence of a delta killing trap: Drift-controlled survival regimes
Alain Mazzolo
We study a one-dimensional diffusive particle subject to
stochastic resetting to its initial position, in the presence of an imperfect, localized target that can absorb (kill) the particle, modeled by a delta-function killing rate. The central question is how
stochastic resetting competes with drift-induced transience and the target's finite reactivity. Exact Laplace-space expressions are derived for the non-normalized propagator and survival probability, for arbitrary
diffusion coefficient $D$, resetting rate $r$, and killing strength $k$, first in the absence of drift and then under a constant drift. The long-time behavior separates into distinct regimes. Without resetting, unbiased
diffusion exhibits the recurrent algebraic survival law $S(t)\sim t^{-1/2}$, whereas any nonzero drift renders the motion transient with respect to the target and leaves a nonzero ultimate survival probability. By contrast, any $r>0$ and $k>0$ repeatedly renews encounters with the target and restores eventual absorption, yielding an exponential survival law $S(t)\sim A e^{-\theta t}$. The decay rate $\theta$ is given by the dominant (rightmost) pole of the Laplace transform, and the surviving density converges after normalization to an explicit quasi-stationary profile. The driftless and perfectly absorbing limits recover standard resetting results. These formulas provide a unified description of the crossover between recurrence-controlled, transience-controlled, and renewal-controlled survival.
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Soft Condensed Matter
Acoustic dip in the effective temperature of hot Brownian motion
Mayank Srivastava and Dipanjan Chakraborty
A hot Brownian particle is driven by thermal fluctuations from a nonuniformly heated solvent and therefore obeys a fluctuation-dissipation relation with a frequency-dependent effective temperature. Existing theories assume an incompressible solvent. We show that finite sound speed qualitatively changes this effective temperature in the kinetic regime. Solving the compressible fluctuating-hydrodynamic problem for a heated sphere, we find that the effective noise temperature develops a pronounced acoustic dip when the sound wavelength becomes comparable to the particle radius. The dip occurs because weakly attenuated longitudinal modes carry mechanical energy away from the heated surface before it is dissipated, so that the dissipation is weighted by colder regions of the temperature field. Its position is set by $a\omega/c=\mathcal{O}(1)$, while its depth is controlled by the dimensionless viscous-acoustic attenuation length $a_c/a$. The result identifies an acoustic window in hot Brownian motion in which compressibility lowers, rather than raises, the kinetic noise temperature.
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Materials Science
Experiments and Modeling of Defect Dynamics and BTI Behavior in Doped InO TFTs during $400^\circ$C Post-Processing Forming Gas Annealing
Yu-Hsin Kuo, Chengyang Zhang, Priyankka Ravikumar et al. (+13 more)
We investigate the impact of a monolithic three-dimensional (M3D) integration process-critical $400^\circ$C post-processing forming gas anneal (FGA) on the electrical performance, reliability, and defect
evolution of oxide-channel thin-film transistors (TFTs), combining systematic experiments with density-functional-theory (DFT)-based
liquid-quench molecular-dynamics (MD) simulations. Indium tungsten oxide (IWO) TFTs are employed as a model system and encapsulated with a thin 3 nm Al$_2$O$_3$ / 3 nm HfO$_2$ hybrid layer that effectively suppresses external hydrogen ingress. We reveal a non-monotonic
evolution of device behavior during FGA, governed by initial densification followed by partial crystallization. Short-duration FGA (10 min) induces channel densification and the formation of shallow, delocalized defect states, leading to pronounced positive bias temperature instability (PBTI) degradation and the emergence of a characteristic transfer-curve "kink." With prolonged annealing (>40 min), partial crystallization of the oxide channel occurs, stabilizing hydrogen in deep, localized defect states, suppressing hydrogen mobility, and restoring device reliability. As a result, the PBTI shift is reduced to 10.4 mV after 2000 seconds of stress, accompanied by complete elimination of the transfer-curve kink. These findings provide a mechanistic understanding of hydrogen-defect interactions during high-temperature post-processing FGA and demonstrate that appropriate hydrogen-blocking encapsulation enables oxide-channel TFT integration without compromising electrical performance or reliability.
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All authors Yu-Hsin Kuo, Chengyang Zhang, Priyankka Ravikumar, Sanghyun Kang, Taeyoung Song, Marco Villena, Luca Larcher, Hwan Kim, Minji Hong, Pilsang Yun, Gaurav Thareja, Shimeng Yu, Daewon Ha, Suman Datta, Julia Medvedeva, Asif Khan
Other Condensed Matter · Cross-listed from quant-ph
Spin-Boson Mappings in the Formalism of $f$-Deformations
Vladimir A. Orlov, Liubov A. Markovich, Andrey V. Mikheyenkov et al. (+1 more)
We develop a unified algebraic approach to
spin-
boson transformations based on the formalism of $f$-deformed oscillators. In the single-mode case, we show that the Holstein-Primakoff and Dyson-Maleev transformations, together with the interpolating $\alpha$-family, arise as different factorizations of the same algebraically determined object. The standard
spin-
boson mappings can thus be interpreted as realizations of a common structure, which makes it possible to clearly separate the exact algebraic content on the physical subspace from effects associated with non-Hermiticity, the choice of metric, and extensions beyond the physical subspace. In the two-mode case, the same approach yields both deformed versions of the Jordan-Schwinger transformation and new exact two-mode realizations. Our results provide a unified description of known
spin-
boson transformations and naturally lead to new bosonic representations.
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All authors Vladimir A. Orlov, Liubov A. Markovich, Andrey V. Mikheyenkov, Vladimir I. Man'ko
Materials Science
Revealing epitaxial relationships at Ga$_2$O$_3$ interfaces with p-type oxides
Anna Sacchi, Krishna Acharya, Michelle A. Smeaton et al. (+5 more)
p-type oxide contact layers such as Cr$_2$O$_3$ and NiO are attracting increasing interest in pn-heterojunctions with n-type monoclinic $\beta$-Ga$_2$O$_3$ for high-power electronic devices and other extreme environment applications. However, scientific understanding of their epitaxial relationships remains incomplete. In this work we investigate the epitaxial relation of Cr$_2$O$_3$ and NiO layers to (001) and ($\bar{2}$01) out-of-plane oriented Ga$_2$O$_3$ substrates. Surprisingly, we find that, for the most commercially relevant (001)-orientation of the Ga$_2$O$_3$ substrate, the epitaxial relationships are Cr$_2$O$_3$ (0001) and NiO (111) $\parallel$ Ga$_2$O$_3$ (101), both at the non-intuitive $\chi$ = 22.5 $^\circ$ angle with respect to the substrate normal. We explain this unusual discovery by the interfacial atomistic bonding dominated by oxygen sublattice equivalence of these Cr$_2$O$_3$ and NiO polar surface orientations to the tilted Ga$_2$O$_3$ (101), rather than Ga$_2$O$_3$ (001) substrate surface planes. Furthermore, we assign the in-plane orientation for Cr$_2$O$_3$ on ($\bar{2}$01)-oriented Ga$_2$O$_3$ as: Cr$_2$O$_3$ $[12\bar{3}0]$ $\parallel$ Ga$_2$O$_3$ $[010]$ with two in-plane rotational domains. Interface modeling confirms the in-plane orientation for Cr$_2$O$_3$/$(\bar{2}01)$ Ga$_2$O$_3$ and shows that strained O-terminated Ga$_2$O$_3$ $(\bar{2}01)$ surfaces have the lowest interfacial energy with Cr$_2$O$_3$ (0001). Beyond establishing the specific epitaxial relationships for Cr$_2$O$_3$ and NiO on Ga$_2$O$_3$, this work provides a systematic methodology for the unambiguous structural characterization of heterointerfaces involving materials with markedly different
crystal symmetries.
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All authors Anna Sacchi, Krishna Acharya, Michelle A. Smeaton, Renae N. Gannon, Vladan Stevanovic, Steven R. Spurgeon, M. Brooks Tellekamp, Andriy Zakutayev
Materials Science
Mobility-lifetime relation links photodegradation in spin-coated and gravure-printed organic solar cells
Maria Saladina, Paul Weitz, David Holzner et al. (+24 more)
The degradation mechanisms of organic solar
cells (OSCs) have been studied primarily in
spin-coated, laboratory-scale devices, whereas scalable processing modifies the device architecture, active-layer morphology, and underlying charge-transport and recombination properties. Whether these changes also alter how solar
cells degrade remains unclear. Here, we compare
spin-coated and fully roll-to-roll-compatible gravure-printed PM6:Y12 solar
cells during $\sim$1000 h of continuous illumination. Despite distinct initial properties and degradation signatures, the loss of power-conversion efficiency systematically follows the mobility-lifetime product $\mu\tau$. Remarkably, ageing of the printed devices increases the recombination lifetime while strongly reducing charge-carrier mobility, showing that a longer lifetime alone does not imply improved device performance. The mobility reduction is accompanied by decreased PM6 lamellar order, whereas the additional open-
circuit voltage loss originates predominantly from increased non-radiative recombination. Dark recovery further reveals a metastable contribution specific to the printed architecture. These results identify the mobility-lifetime product as a unifying physical descriptor for photodegradation, linking ageing-induced microscopic changes to macroscopic performance loss across
spin-coated and scalable printed OSCs.
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All authors Maria Saladina, Paul Weitz, David Holzner, Chen Wang, Robert Eland, Svitlana Taranenko, Christopher Wöpke, Toni Seiler, Fabian Eller, Doyoung Sun, Alexander Ehm, Bekcy Joseph, Peli̇n Çi̇loğlu, Carmen Tretmans, Andreas Willert, Harald Kuhn, Roderick C. I. Mackenzie, Jan-Frederik Pietschmann, Martin Stoll, Yana Vaynzof, Dietrich R. T. Zahn, Safa Shoaee, Eva M. Herzig, Arved Carl Hübler, Thomas Heumüller, Christoph J. Brabec, Carsten Deibel
Materials Science
Laser-Ablated Au Electrodes with Preferred Orientation and Flat Interface on Oxides
Ambrose Seo, Richard Lai, Sujan Shrestha et al. (+5 more)
Gold (Au) thin-film electrodes deposited on oxides by pulsed
laser deposition (PLD) exhibit distinctive structural properties compared with thermally evaporated Au films. While thermally evaporated Au forms polycrystalline films with randomly oriented grains, PLD-grown Au films show a strong preferred [111] orientation perpendicular to the substrate surface, likely due to the energetic nature of the
laser-ablated Au plume. High-resolution transmission electron microscopy reveals atomically flat interfaces between the PLD-grown Au electrodes and epitaxial oxide thin films, separated by nanometer-scale gaps comparable to interlayer spacings in van der Waals materials. The highly ordered microstructure and flat interfacial morphology result in enhanced adhesion of the Au films to oxide surfaces. These results demonstrate that PLD can produce both high-quality Au electrodes and oxide thin films within a single deposition platform, offering improved interfacial control and potential benefits for a wide range of oxide electronic and functional devices.
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All authors Ambrose Seo, Richard Lai, Sujan Shrestha, Tina Tong, Joseph W. Brill, Menglin Zhu, Chris Chae, Jinwoo Hwang
Materials Science
A low-symmetry ground state of dense two-dimensional hydrogen
Cesare Cozza, Chris J. Pickard and Guglielmo Mazzola
Hydrogen under pressure is an extremely complex system featuring molecular dissociation, metallization, and anomalous melting. While bulk hydrogen has been studied for nearly a century, its two-dimensional counterpart remains unexplored. Using first-principles structural searches and relaxations in supercells containing up to 512 atoms, we identify ground-state structures of dense two-dimensional hydrogen showing no evidence of long-range crystalline order over the simulated length scales. Within density functional theory, these structures have lower enthalpy than all crystalline candidates considered over an intermediate pressure interval between molecular and atomic
crystals. This preference already emerges with classical
nuclei and persists as the supercell size increases, while the dominant structure-factor peaks grow substantially more slowly than in the crystalline reference phases. Although
crystals with very large primitive
cells cannot be rigorously excluded, these findings support the possibility of a disordered ground state and identify dense two-dimensional hydrogen as a promising setting for investigating competition between crystallization and structural disorder.
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Strongly Correlated Electrons · Cross-listed from hep-th
Microcanonical Operator Spectrum, BPS Chaos and Free Probability Theory
Alexandre Belin, Yichao Fu and Federico La Rocca
Matrix elements of simple operators are central to thermalization in chaotic
quantum many-body systems. Their moments are often described statistically through the Eigenstate Thermalization Hypothesis. In this paper, we study a more refined characterization of these
matrix elements: the eigenspectrum of simple operators once projected to microcanonical energy windows. The spectrum encodes all moments of the
matrix elements at once, and is particularly relevant when the spectrum of the
Hamiltonian is degenerate. Assuming that the eigenbasis of the simple operator is Haar-randomly oriented with respect to that of the
Hamiltonian, we prove that the spectrum of an operator projected to a small microcanonical window obeys Gaussian random
matrix statistics. We do this directly by studying the probability distribution inherited from the random orientation, as well as using tools from Free Probability Theory. We discuss the implications for BPS chaos and more generally for eigenstate thermalization.
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Strongly Correlated Electrons
Bootstrap certification of string order in quantum spin chains
Sagnik Banerjee, Haoyu Guo and Debanjan Chowdhury
The many-body bootstrap certifies ground-state properties by minimizing energy over correlators constrained only by positivity, without any variational wavefunction. Its cost, however, grows exponentially with the size of the operators involved, placing the long-range string correlators that diagnose topological phases out of reach. We overcome this by treating string operators as primary objects: bare and endpoint-dressed strings satisfy a closed operator
algebra with one another and with local words, yielding a semidefinite program whose cost grows only polynomially with string length. A single computation then yields estimates of string correlators of all lengths. Rigorous two-sided bounds are obtained for each target string once the ground-state energy is pinned within a window. When benchmarked against density-
matrix renormalization group computations on the cluster Ising and
spin$-1$ Heisenberg chains, the method certifies the nonlocal string order of the cluster and Haldane phases directly from the
Hamiltonian. Our rigorous certification of string order parameters reveal that the sharpness of the bounds is set by which operators enter the calculation, not by their length alone. By exploiting algebraic closure of strings and local words, our framework lifts spatially extended observables into polynomially tractable bootstrap variables, opening up a route to wavefunction-free certification of nonlocal order in
quantum many-body systems.
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Materials Science · Cross-listed from eess.IV
AutoRASOR: Autonomous Rapid Scanning Electron Microscope Operator
Kevin Zhang, Mohammad Taha, Rafael Espinosa Castañeda et al. (+7 more)
Scanning Electron Microscopy (SEM) is a foundational technique for characterizing material microstructure, which dictates many fundamental physical and chemical properties. With the rise of Self-Driving Labs (SDLs), samples are now synthesized in large batches, demanding equally high-throughput, autonomous characterization. Existing automated electron microscopy pipelines are task-specific: they detect pre-defined features, optimize known properties, or require prior knowledge of the sample, restricting each pipeline to the material system it was built for. We introduce AutoRASOR, a task-agnostic autonomous SEM pipeline that captures the multi-scale morphology of an unknown sample without domain-specific pre-training, fine-tuning, or human prompting. AutoRASOR embeds micrographs in real time with a
vision foundation model (VFM), DINOv3, and selects regions of interest (ROIs) through two complementary policies: Latent Farthest Point Sampling (LFPS) and active learning on morphological ambiguity, which is the conditional variance of unresolved fine-scale features given lower magnification appearance. Active learning on ambiguity consistently captures more diverse and rare morphologies than random ROI selection, while LFPS reliably recovers the specimen's morphological distribution within a limited capture budget, tested both on real SEM micrographs and synthetic phase-field images. By shifting autonomous characterization from pre-defined, task-specific targeting of features to morphological survey, AutoRASOR generates information-rich multi-scale
datasets for diverse downstream tasks. Without the need for domain-specific pre-training or prior material assumptions, this framework can be deployed out-of-the-box to characterize novel materials produced by SDLs.
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All authors Kevin Zhang, Mohammad Taha, Rafael Espinosa Castañeda, Yutong Liu, Yin Zhu, Lotan Portal, Robert A. Mcleod, Vahid Attari, Jane Y. Howe, Jason Hattrick-Simpers
Superconductivity
Raman scattering in cuprate oxychlorides high-temperature superconductors single-crystals
Chafic Fawaz, Yingzheng Gao, Luca Laveder et al. (+13 more)
We investigate the Raman response of sodium-doped cuprate oxychloride Na$\_x$Ca$\_{2-x}$CuO$\_2$Cl$\_2$ high-temperature
superconductors across their entire phase diagram, from the antiferromagnetic to the superconducting region. In addition to the expected Raman-active
phonon modes, we detect several additional modes that can be interpreted as being excited via a resonance process enabled by strong electron–
phonon coupling. To verify the resonance effect, the Raman response at different incident
photon energies was measured. At high energies, there is a well-defined $B\_{1g}$ mode in the antiferromagnetic phase, which can be interpreted as a bimagnon We follow its temperature and doping dependence, providing information on the multimagnon excitation in these cuprates, which can be theoretically linked to the exchange interaction.
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All authors Chafic Fawaz, Yingzheng Gao, Luca Laveder, Lorenzo Menon, Owen Moulding, Rolf Heid, Blair W Lebert, Christophe Bellin, Keevin Beneut, David Santos-Cottin, Ikuya Yamada, Yuichi Okazaki, Hajime Yamamoto, Masaki Azuma, M.-A. Méasson, Matteo d'Astuto
Materials Science · Cross-listed from cs.SD
Causal limits and optimal allocation for passive frequency-selective hearing protection
Geonhwi Hwang, Jaewoo Lee, Hyunjun Kim et al. (+1 more)
Passive Helmholtz-resonator earplugs aim to attenuate hazardous noise while keeping
speech audible; the air volume of an ear-sized shell is finite, and we treat it as the resource a design spends. For a vented bore transparent at zero frequency and loaded by reactive side branches, causality fixes a conserved integral of transmission loss. We derive it in device variables, add viscous and flanking constraints, and allocate the budget by hazard-weighted water-filling with a continuous
speech-cost price. The audio-band budget B_ad = (20/ln10) pi^2 V / 2cS is set by the ratio of total cavity volume V to bore area S; occluding plugs are exempt. The f^2 price signal favours frequencies well above the source peak. Replacing strict transparency by a
speech-cost price gives an exchange rate of about 1.3 dB of protection per decibel of
speech cost under the present model, with the budget setting where it saturates. Across three form factors, low-frequency-selective designs stay near a decibel while hazard-matched mid/high-frequency designs reach twelve. The binding variables are bore area and
speech allowance, not resonator count.
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All authors Geonhwi Hwang, Jaewoo Lee, Hyunjun Kim, Hyeonwoo Na
Soft Condensed Matter
On the ratio between longitudinal and transverse Ioffe-Regel frequencies in glasses
Licun Fu, Mingyu Zhu, Xinyu Chang et al. (+1 more)
The temperature dependence of thermal conductivity in glasses differs characteristically from that in
crystals, and is largely controlled by how sound waves are damped. The Ioffe-Regel (IR) frequency sets the high-frequency limit of well-defined sound waves. Although the transverse IR frequency has been established to coincide with the
boson peak frequency and reported to be far below the longitudinal IR frequency, the quantitative relation between longitudinal and transverse IR frequencies has remained unknown. Here we examine this relation in two- (2D) and three-dimensional (3D) model glasses with vastly different stability. We observe that, in 3D glasses, the longitudinal-to-transverse IR frequency ratio is approximately equal to the ratio of the low-frequency transverse to longitudinal sound attenuation coefficient, whereas this correspondence is not observed in 2D glasses. Moreover, we find that the glass stability strongly controls the longitudinal-to-transverse IR frequency ratio in both 2D and 3D glasses: the ratio decreases significantly with increasing glass stability and approaches unity for the most stable glasses under study. Accordingly, in sufficiently stable glasses, the longitudinal sound attenuation should be comparable to the transverse attenuation, and therefore cannot be treated as negligible, challenging common assumptions adopted especially in theoretical studies. Our work is another demonstration of the glass stability as a key parameter for investigating glass properties, and cautions against simply extrapolating observations from poorly annealed glasses to stable glasses.
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All authors Licun Fu, Mingyu Zhu, Xinyu Chang, Lijin Wang
Statistical Mechanics
Universal Eigenvector Statistics of Non-Hermitian Random Matrices
Ze Chen, Zhenyu Xiao and Shinsei Ryu
Eigenvector overlaps quantify nonorthogonality and govern the response and dynamics of non-Hermitian systems. We extend the universality of non-Hermitian random
matrices to the statistics of these overlaps. We obtain analytical expressions for eigenvector overlaps in the spectral bulk and near the origin, covering ten
symmetry classes in the limit of large
matrix size. Using fermionic replica nonlinear $\sigma$ models, we relate these overlaps to Hermitian level statistics,
symmetry class by
symmetry class and topological sector by topological sector. Numerical calculations in various physical models support the universality of the normalized overlaps in the regimes studied. Our work establishes a duality between Hermitian level statistics and non-Hermitian eigenvector overlaps.
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Strongly Correlated Electrons
Correlation enhanced magnetism at a superconducting cuprate/manganite interface
Vitor A. M. Lima, Marcello Civelli and Walber Hugo de Brito
Motivated by experimental studies on cuprate-manganite
heterostructures, we study a correlated bilayer Hubbard model subject to a local interfacial exchange field using cluster dynamical mean-field theory in the underdoped cuprate regime. We find that superconductivity coexists with a manganite-induced Cu
spin polarization. Remarkably, throughout this coexistence regime, the superconducting solution carries a larger
magnetic moment than the corresponding constrained normal state. Analysis of the
magnetic response shows that this reversal is driven by correlations, which enhance magnetism already in the normal state and even more strongly in the superconducting solution. At stronger exchange fields, superconductivity collapses abruptly, displaying hysteresis consistent with a first-order transition, and a strongly
spin-polarized pseudogap emerges. These results show that, under strong electronic correlations, superconductivity can enhance rather than suppress interfacial magnetism.
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Materials Science
Symmetry Classification of Multipolar Orders in Crystals: Theory, Property Tensors and Automated Analysis with MagSymMultipoles
Maxime Braun and Quintin N. Meier
Many structural and
magnetic phases and properties of crystalline materials can be related to the ordering of electric and
magnetic multipoles. Examples include ferroelectricity, linear magnetoelectricity, and altermagnetism. Determining the
symmetry-allowed multipoles in a
crystal is therefore useful for characterizing its ordered phases and physical properties. Here, we present a unified Cartesian framework for decomposing moment tensors of arbitrary rank into ordinary, toroidal, and poloidal multipoles, and for determining, from crystallographic and
magnetic symmetry, their ferroic, antiferroic, and noncollinear arrangements within the
crystal. We further establish the direct
symmetry relationship between multipolar order and the allowed components of associated physical-property tensors in both relativistic and non-relativistic settings. We implement this methodology in MagSymMultipoles (https://mag-sym-multipoles.com), an interactive web application for calculating and visualizing
symmetry-adapted electric and
magnetic multipoles. The application uses
magnetic symmetries both with and without
spin-orbit coupling to derive the allowed multipoles as well as the underlying Cartesian moment tensors, making it easy to explore the connection between a given multipolar order and the corresponding physical response tensors. We demonstrate the approach for ferroelectric BaTiO3, antiferroelectric PbZrO3, magnetoelectric Cr2O3, and the altermagnets MnF2, MnTe, and Mn3IrSi. These examples demonstrate how our method allows us to obtain an intuitive picture linking the multipolar order of a material directly to its physical properties, thereby facilitating the interpretation of theoretical and experimental results.
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Mesoscale and Nanoscale Physics
Non-Hermitian impurity scattering in graphene: Boltzmann transport and thermoelectric response
Juan A. Cañas, Daniel A. Bonilla and A. Martín-Ruiz
We investigate charge and thermoelectric transport in monolayer
graphene containing a dilute distribution of finite-range non-Hermitian scattering centers. The impurities are modeled as circular complex potentials, whose imaginary component describes local carrier loss or gain. By solving the Dirac scattering problem exactly within a partial-wave approach, we obtain the nonunitary scattering
matrix and derive the transport and absorption cross sections, which separately characterize momentum relaxation and net carrier exchange with the environment. To connect the microscopic scattering problem with stationary transport, we formulate a semiclassical Boltzmann description in which an external reservoir compensates the
equilibrium particle loss or gain. This leads to an effective relaxation time governed by both elastic momentum scattering and non-Hermitian flux exchange. Using the full energy-dependent relaxation time, we evaluate the Onsager coefficients and the resulting electrical conductivity, electronic thermal conductivity, Seebeck coefficient, Lorenz ratio, and electronic thermoelectric figure of merit. We find that weak gain increases the effective carrier lifetime and enhances both charge and heat conductivities, while absorption produces the opposite behavior. More importantly, gain enhances the magnitude of the thermopower and the electronic figure of merit, whereas loss suppresses them. The Lorenz ratio remains close to the Sommerfeld value, with non-Hermiticity mainly modifying its finite-temperature corrections. Our results show that non-Hermitian scattering provides an additional mechanism for controlling the energy dependence of carrier relaxation and, consequently, the thermoelectric response of
graphene.
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Materials Science
Insights into the long-standing controversy over sound velocities in lizardite
Chenxing Luo, Timothy Liao, Hongjin Wang et al. (+1 more)
Serpentine minerals are abundant H-bearing phases in the upper mantle and play a central role in water transport in subduction zones. Lizardite is the low-temperature polymorph expected in cold slabs and shallow serpentinized mantle. Using an ab initio thermoelastic framework combining density-functional theory with the r2SCAN meta-GGA and the quasiharmonic approximation, we calculate its compression curve, elastic tensor, and acoustic velocities at 300 K. r2SCAN reproduces the measured compression curve and
equilibrium volume to within 0.2%. Weak interlayer hydrogen bonding gives rise to pronounced axial softening, with $C_{33} \simeq 0.21C_{11}$ and $C_{44} \simeq 0.13C_{66}$ at 0 GPa. Solving the Christoffel equation over all propagation directions, we construct the velocity density of states (VelDOS), which reveals a high density of slow acoustic modes and other directional features obscured by Voigt-Reuss-Hill (VRH) aggregate averages. Reported experimental velocities preferentially sample the slower portion of this distribution rather than clustering near the VRH values, a correspondence consistent with subtle crystallographic texture or preferential orientation not resolved experimentally. Thus, the appropriate seismic-velocity endmember for lizardite depends on its orientational state, and reliance on VRH velocities alone may lead to overestimation of the degree of serpentinization when seismic observations preferentially sample slow crystallographic directions. Direction-resolved single-
crystal measurements and aggregate measurements with independently quantified texture would provide direct tests of this interpretation.
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All authors Chenxing Luo, Timothy Liao, Hongjin Wang, Renata M. Wentzcovitch
Mesoscale and Nanoscale Physics
Photogalvanic effect in monolayers of transition metal dichalcogenides
G.V. Budkin and E.L. Ivchenko
We present a theoretical study of photocurrents generated by direct optical transitions induced by linearly polarized radiation in monolayers of transition metal dichalcogenides. A microscopic theory of both the ballistic and shift contributions to the photocurrent is developed that accounts for Coulomb attraction between photoexcited electrons and holes. It is demonstrated that, in typical 2D
semiconductors, the Coulomb correlation causes the ballistic contribution to dominate over the shift photocurrent.
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Soft Condensed Matter
Merons Mediate Re-Ordering of Curved Rods Under Shear Flow
Nicholas W. Hackney, Joel T. Clemmer, Thomas O'Connor et al. (+1 more)
Bent-core
liquid crystals are a canonical example of a soft matter system whose behavior is controlled by a local preference for order that cannot be universally achieved. This
geometric frustration, arising from the rod's curved shape, has been shown to stabilize a variety of
equilibrium phases, such as the helically ordered nematic twist-bend phase ($N_{\rm TB}$). Unlike a traditional nematic, the twist-bend state has 1D translational order arising from a periodic rotation of bend orientation along the helical axis. Here, we use molecular dynamics simulations to study the effect of shearing the $N_{\rm TB}$ phase along directions parallel and perpendicular to the helical axis. In the case of shear perpendicular to the helical axis, the nematic twist-bend phase is stable and flows without disordering. Conversely, shear along the helical axis disrupts order and leads to the emergence of fractionally charged Skyrmion defects, i.e. merons. These defects act as topological machines, locally rotating rods into a re-ordered and stable orientation of the $N_{\rm TB}$ phase. These findings reveal a new mechanism to create and control merons and highlight the potential application of bent-core
liquid crystals in designing functional material with specific optical and computational properties.
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All authors Nicholas W. Hackney, Joel T. Clemmer, Thomas O'Connor, Gary S. Grest
Materials Science
PAOFLOW: an automated suite for ab initio electronic, transport, and topological properties of materials
Anooja Jayaraj, Sergio Alvarruiz, Mia Falatko et al. (+10 more)
High-throughput first-principles property calculations are often constrained by costly post-processing and dense Brillouin-zone sampling, impeding the creation of large, internally consistent materials-property
datasets and limiting AI-driven discovery workflows. Pseudo-atomic-orbital (PAO)
Hamiltonians provide an exact tight-binding representation of first-principles electronic structure that enables the calculation of a wide range of electronic, optical, topological, and transport properties at negligible cost, thereby supporting scalable generation of training-quality data and AI-ready data infrastructures. In this work, we present PAOFLOW 3.0 – an open-source Python suite that automates the construction and analysis of PAO
Hamiltonians from plane-wave density functional theory calculations performed with either
Quantum ESPRESSO or VASP. The resulting
Hamiltonians enable efficient electronic structure interpolation, Fermi surface analysis, optical and dielectric response, transport coefficients, Berry phase and topological quantities,
quantum transport, and other materials properties. Compared with previous releases, PAOFLOW 3.0 substantially extends the scope of the package through the introduction of internal projections enabling support for VASP calculations, self-consistent Hubbard U and V corrections obtained using ACBN0 and eACBN0 methods, generation of environment-dependent Slater-Koster tight-binding models, Landauer–BÃŒttiker
quantum transport, and calculation of
quantum oscillations using the integrated PySKEAF module. The theoretical foundations and the software architecture are presented together with representative calculations illustrating the current capabilities of the package.
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All authors Anooja Jayaraj, Sergio Alvarruiz, Mia Falatko, Zhiren He, Jonathan Red, Caua F. Schuch, Karma Tenzin, Chao Chen Ye, Davide Ceresoli, Marcio Costa, Stefano Curtarolo, Jagoda Slawinska, Marco Buongiorno Nardelli
Strongly Correlated Electrons
Unified Field Bosonization Technique for strongly inhomogenous Luttinger Liquids
Soundarya P, Venkata Suryanarayana M and Joy Prakash Das
We introduce the Unified Field Bosonization Technique (UFBT), a direct bosonization framework for strongly inhomogeneous one-dimensional Luttinger
liquids (LLs) containing static impurities. UFBT incorporates impurity scattering through a symmetrized combination of bosonic phase fields and yields closed-form expressions for arbitrary N-point correlation functions for a broad class of static impurity potentials, including delta barriers, finite barriers and finite wells. The formalism requires neither renormalization-group analysis nor perturbative expansions, providing an analytical description of the inhomogeneous system at the bosonized level. The resulting correlation functions capture the leading singular contributions relevant to the present analysis. The technique is validated by recovering known limiting cases, showing agreement with the first-order perturbative expansion in the interaction strength, and demonstrating consistency with the Schwinger-Dyson equations. A key result is that the correlation function exponents remain independent of the impurity strength, while the impurity dependence is captured by the spatial structure and amplitudes of the correlation functions. The resulting correlation functions establish a foundation for analytical studies of transport, Friedel oscillations, and the local and dynamical density of states in strongly inhomogeneous Luttinger
liquids.
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Materials Science · Cross-listed from physics.chem-ph
Development of a Non-Empirical Exchange-Hole Dipole Moment Dispersion Model
Alastair J. A. Price and Alberto Otero-de-la-Roza
The inclusion of dispersion effects is important in density-functional theory (DFT) to model non-covalent interactions correctly, a task that is essential in many applications of the theory. Many dispersion functionals have been proposed in the past. The exchange-hole dipole moment (XDM) model combines the simplicity of a damped pairwise asymptotic expression for the dispersion energy with a theory-grounded approach to calculate the dispersion coefficients. XDM is, arguably, the most accurate dispersion correction for the description of molecular
crystals and it has been thoroughly tested for other applications across a wide range of chemistries. Here, we address the two main shortcomings of XDM. First, XDM relies on the use of experimentally determined free-atom polarizabilities. Second, because the XDM atom-in-molecule properties (volumes, polarizabilities, exchange-hole dipole moments) use the Hirshfeld partition method, XDM describes systems with large atomic partial charges, like alkali cations or halide anions, poorly. We propose neXDM, a non-empirical variant of XDM that removes the experimental parameters by using the Kirkwood polarizability formula, thereby making neXDM a pure meta-GGA dispersion functional. In addition, following previous work by Bučko et al. on the similar Tkatchenko–Scheffler (TS) method, we replace the Hirshfeld partitioning with its iterative counterpart. The performance of neXDM is shown to be on par with XDM in standard molecular and
crystal benchmark sets, and greatly improves the modeling of ionic systems. The new neXDM method sets a new record for the best dispersion-corrected generalized-gradient approximation (GGA) functional for molecular
crystal lattice energies in the X23 set (0.700~kcal/mol).
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