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Physics Condensed Matter

cond-mat Watch Condensed Matter

Sunday 29 March

Mesoscale and Nanoscale Physics · Cross-listed from quant-ph

Resonant excitation of single and coupled qubits for coherent quantum control and microwave detection

O.A. Ilinskaya and S.N. Shevchenko

Resonant driving enables coherent control of quantum systems, including single and coupled qubits. From a complementary perspective, transitions of a quantum system can be exploited for the detection of microwave photons. In this work, we theoretically investigate resonant multiphoton excitations in a system of qubits. When the energy of K photons matches the energy splitting of the qubit system, the absorption of these photons leads to collective excitation of the qubits. We focus on the case of two coupled qubits and analyze the quantum dynamics of both excitation and relacation processes. In the particular case where only a single qubit is relevant and the remaining qubits can be neglected, the dynamics admits an analytical treatment. We examine multiphoton resonances, the Bloch-Siegert shift, and population inversion, phenomena that are central to both coherent quantum control and microwave photon detection.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph

Quantum control and signal enhancement exploiting the Stokes-anti-Stokes coherence

Wen-Zhao Zhang, Keye Zhang and Jie Li

We present a theoretical framework for the coherent coupling between Stokes and anti-Stokes scattering processes, revealing interference phenomena inaccessible to either process alone. Within a dispersive-interaction model beyond the resolved-sideband limit, we show that classical driving and system linewidth coherently links the two channels, enabling phase-controlled interference. Destructive interference induces intrinsic asymmetry in dispersively coupled systems, enabling coherent control of quantum information storage and transfer, while constructive interference leads to exponential signal amplification and thus enhanced quantum detection. This work establishes a unified picture for understanding Stokes-anti-Stokes coherence as a fundamental mechanism underlying both quantum control and metrology. Furthermore, it suggests that these functionalities can be further enhanced by implementing Stokes-anti-Stokes arrays.
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Statistical Mechanics · Cross-listed from math.PR

The spectrum of the stochastic Bessel operator at high temperature

Laure Dumaz and Hugo Magaldi

Ramírez and Rider (2009) established that the hard edge of the spectrum of the $\beta$-Laguerre ensemble converges, in the high-dimensional limit, to the bottom of the spectrum of the stochastic Bessel operator. Using stochastic analysis tools, we prove that, in the high-temperature limit ($\beta \to 0$), the rescaled eigenvalue point process of this operator converges to a non-trivial limiting point process. This limit is characterized by a family of coupled diffusions and differs from a Poisson point process due to its interaction with the hard edge. Exploiting this diffusion characterization, we establish exact large deviation asymptotics for the largest eigenvalues. Furthermore, for an explicit range of the parameters, we relate this limiting process to the finite-$n$ $\beta$-Laguerre ensemble, conjecturing an exact distributional match with the infinite sum of its independent exponential gaps. As a byproduct of our analysis, we also formulate a conjecture regarding an explicit integral formula for the probability that a reflected Brownian motion with a constant drift hits an affine line, generalizing a formula of Salminen and Yor (2011).
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Materials Science

First-order polarization process as an alternative to antiferroelectricity

Louis Bastogne, Lukas Korosec, Yuchuan Wang et al. (+7 more)

Antiferroelectrics generate significant interest since their polarization versus electric field (P-E) curves show typical double-hysteresis loops appealing for various applications. Unfortunately, antiferroelectrics are rare. In magnetic compounds, magnetization versus magnetic field (M-H) curves can show analogous double hysteresis loops not only in antiferromagnets but also in systems exhibiting field-induced first-order reorientation of the magnetization through a so-called first-order magnetization process. Here, we show that appealing double-hysteresis P-E loops can also appear from an unprecedented first-order polarization process. Focusing on non-polar CaTiO3, which can be turned ferroelectric under tensile strain, we study epitaxial thin films on differently-oriented NdGaO3 substrates using a combination of theoretical and experimental techniques. We uncover that a certain configuration exhibits double-hysteresis P-E loops that we rationalize from a field-induced abrupt rotation of the polarization. Such a first-order polarization process establishes a promising alternative pathway to achieve double hysteresis P-E loops appealing for practical applications.
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All authors Louis Bastogne, Lukas Korosec, Yuchuan Wang, Evgenios Stylianidis, Daniel G. Porter, Gareth Nisbet, Clémentine Thibault, Jean-Marc Triscone, Marios Hadjimichael, Philippe Ghosez

Materials Science

Anomalous Hall Conductivity as an Effective Means of Tracking the Floquet Weyl Nodes in Quasi-One-Dimensional $\beta$-Bi$_4$I$_4$

Qingfeng Huang, Shengpu Huang, Tingyan Chen et al. (+5 more)

While Floquet engineering offers a powerful paradigm for manipulating topological phases, particularly Floquet Weyl semimetals, establishing an experimentally feasible strategy for tracking the dynamic evolution of such states remains a significant challenge. Here, we propose that the anomalous Hall effect (AHE), as a sensitive, all-electrical probe, can be used to track Floquet Weyl nodes. Using first-principles calculations and symmetry analysis on the quasi-one-dimensional material $\beta$-Bi$_4$I$_4$, we demonstrate that circularly polarized light breaks time-reversal symmetry, driving the system from a trivial insulator into a Floquet Weyl semimetal phase characterized by a nonzero Berry curvature flux. Crucially, by continuously tuning the polarization phase $\varphi$ of the driving field, we show that the trajectory of the induced Weyl nodes is highly controllable, leading to their migration and eventual annihilation at high-symmetry points. We reveal that the anomalous Hall conductivity maps directly onto this topological evolution, serving as a definitive fingerprint for the generation and dynamics of Weyl nodes.
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All authors Qingfeng Huang, Shengpu Huang, Tingyan Chen, Jing Fan, Dong-Hui Xu, Xiaozhi Wu, Da-Shuai Ma, Rui Wang

Materials Science

Light-Tunable Giant Anomalous Hall Effect in the Flat-Band Magnetic Weyl Semimetal $\mathrm{AlFe_2O_4}$

Tingyan Chen, Shengpu Huang, Jing Fan et al. (+3 more)

Achieving a giant anomalous Hall effect (AHE) and enabling its effective tuning are fundamental goals for topological spintronics. Magnetic Weyl semimetals hosting flat bands offer a promising route to maximize the AHE. However, while theoretical models are well-established, realistic material candidates remain scarce. Since the intrinsic anomalous Hall conductivity (AHC) is topologically dictated by the momentum separation ($\kappa$) between Weyl nodes, actively manipulating remains a key challenge. Here, through comprehensive first-principles calculations, we establish the inverse spinel $\mathrm{AlFe_2O_4}$ as a realistic ferromagnetic half-metallic platform integrating three-dimensional flat bands and Weyl physics. Spin-orbit coupling induces a single pair of Weyl nodes, yielding a giant intrinsic AHC of $398\ \mathrm{S}\cdot\mathrm{cm}^{-1}$. By constructing a symmetry-constrained tight-binding model, we uncover a deterministic relationship between microscopic electronic couplings and the macroscopic AHE. Exploiting this via Floquet engineering with circularly polarized light, we demonstrate that the effective couplings are dynamically suppressed. This optical modulation controllably enlarges $\kappa$, shortens the topological Fermi arcs, and drives a dramatic, quantitative suppression of the AHC, providing a practical blueprint for ultrafast, light-controlled topological transport.
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All authors Tingyan Chen, Shengpu Huang, Jing Fan, Dong-Hui Xu, Rui Wang, Da-Shuai Ma

Materials Science

The rise of unconventional magnetism

Xiaobing Chen, Weizhao Chen and Qihang Liu

Unconventional magnetism represents a paradigm shift in condensed matter physics, effectively bridging the fast, high-density advantages of antiferromagnets with the facile read-write capability of ferromagnets. Recent developments in spin space group theory have established a systematic methodology to decouple magnetic geometry from relativistic spin-orbit coupling, driving the exploration of unconventional magnets that exhibit compensated magnetization with time-reversal-odd responses. Here, we review unconventional magnetism across three pivotal facets in momentum space: spin textures, quantum geometry, and emergent quasiparticles. From the perspective of symmetry analysis, we elucidate the mechanisms underlying time-reversal-odd physical responses, including non-relativistic spin splitting, anomalous and nonlinear Hall effects, and exotic electronic and magnonic topological phases. Finally, we provide a forward-looking perspective on coupling unconventional magnetism with ferroelectricity, superconductivity, and moiré engineering. By exploiting symmetry-driven insights, this review highlights the functional potential of unconventional magnets in developing next-generation, high-speed, and energy-efficient spintronic devices.
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Quantum Gases · Cross-listed from physics.atom-ph

High performance imaging of $^{171}$Yb atom in shallow clock-magic tweezer by alternating dual-tone narrowline cooling

Yunheung Song, Kangheun Kim, Jeong Ho Han et al. (+2 more)

We demonstrate imaging $^{171}$Yb single atoms in clock-magic tweezers of 759.4 nm wavelength, with above 99.9% fidelity and survival. We use alternating dual-tone narrowline imaging for more efficient three-dimensional cooling in tweezers, allowing several-millisecond imaging in 200 $\mu$K trap depth, which is half of typical depth used for imaging in clock-magic tweezers. Accordingly, even without repumping, imaging survival is still close to 99.9% with the high fidelity, which can enable high performance nondestructive qubit measurements based on metastable shelving. Moreover, our simulation predicts that more optimal configuration could further reduce the trap depth, as improving the imaging performance. This imaging capability in shallow traps opens high performance imaging for more general trap wavelength, and lays the foundation for large scale systems over 1,000 qubits, and highly repeatable tweezer clocks.
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All authors Yunheung Song, Kangheun Kim, Jeong Ho Han, Seungtaek Oh, Jongchul Mun

Statistical Mechanics

Microscopic Pathways to Helix Formation: Packing Stabilization and Sticky Interactions in Chiral Polymer Condensates

Biman Bagchi

Helices are not generic outcomes of polymer collapse. Collapsed conformations of semiflexible polymers with isotropic attractions typically form globules, toroids, or rod-like structures, as seen in simulations and described by coarse-grained necklace and surface-tension models. Helical conformations, in contrast, are generally absent in minimal theories based solely on bending elasticity and isotropic cohesion, since such descriptions lack any mechanism to select torsion, pitch, or periodic packing. Here we identify two minimal and physically distinct routes by which helices can become stable without invoking biochemical specificity. Route (A) is geometric and steric: combining a tube-like packing (thickness) constraint with generic attractions selects an ideal helical packing with finite radius and pitch. Left- and right-handed helices remain exactly degenerate in free energy, so chirality emerges spontaneously even without explicit chiral interactions. Route (B) is energetic and commensurate: periodic "sticker" attractions between monomers separated by a fixed contour distance $m$ enforce a registry between interaction spacing and chain geometry. This commensurability stabilizes helical states by enabling repeated contacts along the backbone, naturally connecting to classical Gibbs-DiMarzio and Zimm-Bragg mechanisms. For both routes, we derive analytical relations for helix radius and pitch, curvature and bending energy, contact-distance constraints, and crossover conditions to toroidal and rod-like morphologies, expressed in terms of persistence length $L_p$, interaction strength, and chain length $N$. This framework explains why helices are non-generic in polymer collapse, identifies the physical ingredients required for their stabilization, and provides testable predictions for when helical and chiral condensates should emerge.
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Soft Condensed Matter

Unidirectional flow from continuous broken symmetries

Aaron Winn, Justine Parmentier, Eleni Katifori et al. (+1 more)

Locally broken symmetries are used across fields to transport matter, particles and information in preferential directions. Beyond local mechanisms, spatially distributed nonlinearities in crystalline media have enabled non-reciprocal transport, a rectification mechanism that operates continuously across scales and frequencies. Here, we show that this concept applies beyond condensed matter, to fluid transport in living organisms and artificial systems. We take the example of the lymphatic vascular system, which transports interstitial fluid in mammals, and demonstrate that distributed leaflets act as continuous broken symmetries. We build an artificial model of a collecting lymphatic and investigate the naturally richer dynamics of unidirectional transport that arises from spatiotemporal excitations. We observe robust and scalable transport for any waveshape and external pressure gradients. We show experimentally and theoretically that the contraction wavelength, directionality, and pulsatility control the flow rate. In particular, we counterintuitively find waveshapes that maximize transport when propagating against the direction of the flow. Overall, our findings advance the understanding of unidirectional fluid transport in living systems and beyond, and reveal how coupling nonlinearities with spatiotemporal excitations can tune such transport across fields.
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All authors Aaron Winn, Justine Parmentier, Eleni Katifori, Martin Brandenbourger

Other Condensed Matter

Characterizing the Linearity of Magnonic Devices for Radio-Frequency Applications

Robert Erdelyi, Adam Papp Levente Maucha, Philipp Pirro et al. (+5 more)

Magnonic devices exhibit strong amplitude-dependent nonlinearities, which are detrimental to signal integrity in radio-frequency (RF) signal processing applications. They also limit the power that such magnonic devices may process. In this paper we use micromagnetic simulations to characterize the nonlinearity of magnonic RF devices by investigating their intermodulation distortion (specifically third-order intermodulation products, IP$_3$ ). The IP$_3$ is a commonly used metric for RF components in communication systems and allows direct comparison with state-of-the-art electrical counterparts.
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All authors Robert Erdelyi, Adam Papp Levente Maucha, Philipp Pirro, Matthias Wagner, Dieter Ferling, Johannes Greil, Markus Becherer, Gyorgy Csaba

Strongly Correlated Electrons

Electronic structure of higher-order layered palladates: La$_{n+1}$Pd$_{n}$O$_{2n+2}$ $(n = 4-7)$

Alexander K. Gavrilov, Lidia C. Santander and Antia S. Botana

The square-planar layered nickelates R$_{n+1}$Ni$_n$O$_{2n+2}$ (R= Nd, $n=4-7$) have been recently shown to be superconducting without the need for chemical doping or pressure. Here, we examine the electronic structure of the analog higher-order square-planar palladates – that have not yet been synthesized – via ab initio calculations. These layered palladates exhibit larger bandwidths, an increased $p-d$ hybridization, and less interference from R-$d$ bands at the Fermi level. These characteristics make them closer cuprate analogs and promising candidates to pursue in the context of unconventional superconductivity.
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Materials Science

Twist-Angle Engineering of Moiré Potentials for High-Performance Ionics in Bilayer Graphene

Gen Fukuzawa, Yebin Lee and Teruyasu Mizoguchi

Controlling ion transport is a fundamental challenge for advanced energy storage. Bilayer graphene offers a unique platform for modulating ion diffusion via twist-angle-dependent moire superlattices, yet conventional stacking configurations face an inherent trade-off: AA stacking provides stable Li intercalation but high diffusion barriers, while AB stacking enables fast diffusion but poor intercalation stability. Twisted bilayer graphene (tBLG) offers potential to overcome this limitation, yet systematic understanding across different twist angles remains limited. Here, we investigate Li intercalation in tBLG using first-principles density functional theory, evaluating intercalation energies and diffusion barriers across multiple twist angles through potential energy surface (PES) mapping. The Sigma 37 structure (9.43 degrees) simultaneously achieves the most favorable intercalation energy (-2.39 eV) and the lowest diffusion barrier (0.14 eV) among all structures examined, resolving the conventional stacking trade-off. Furthermore, using the Smooth Overlap of Atomic Positions (SOAP) descriptor, we demonstrate that the PES is governed by local atomic environments and that a model trained on limited structures predicts the PES of untested configurations with high accuracy. This transferability enables efficient screening without exhaustive first-principles calculations, establishing a systematic framework for twist-angle engineering of ion transport in two-dimensional layered materials.
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Saturday 28 March

Materials Science · Cross-listed from physics.geo-ph

Olivine annealed up to 1500 C: changes traced by polarised IR reflectance and magnetization

Daniel Smith, Donatas Narbutis, Hsin-Hui Huang et al. (+14 more)

Spectral analysis at the infrared (IR) spectral range is introduced with assignment of synthetic red-green-blue (RGB) colours defined by adjustable wavelength and bandwidth. The RGB bands were selected at the phase-specific absorbance A or reflectance R bands of olivine and related materials, which can be formed via high temperature annealing (HTA) of natural minerals up to 1500 C. Natural olivines were collected from quarry at volcanic site in Mortlake, Victoria, Australia and spectrally characterised during IR-THz spectroscopy beamtime experiments at Australian Synchrotron. Phase changes in HTA natural olivines were traced by correlation of optical IR 4-polarisation spectroscopy, X-ray energy dispersive spectroscopy and magnetisation. After HTA, olivine samples were magnetized via precipitation of Fe-rich oxides.
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All authors Daniel Smith, Donatas Narbutis, Hsin-Hui Huang, Philipp Zanon, Michael Boschen, Jitraporn Vongsvivut, Dominique Appadoo, Soon Hock Ng, Haoran Mu, Tomas Katkus, Nguyen Hoai An Le, Dan Kapsaskis, Andy I.R. Herries, Vijayakumar Anand, Meguya Ryu, Junko Morikawa, Saulius Juodkazis

Mesoscale and Nanoscale Physics · Cross-listed from physics.class-ph

Induced-current magnetophoresis

V. Kumaran

When an electrically conducting non-magnetic particle is subjected to a spatially varying and oscillating applied magnetic field of amplitude $\mathcal{H} + \mathcal{G} \cdot x$ and frequency $\omega$, an oscillating eddy current is induced. The Lorentz force density, the cross product of the current density and the magnetic field, consists of a steady component and a component with frequency $2 \omega$. If there is a spatial variation in the applied field, there is a steady force on a sphere of radius $R$ proportional to $- \mu_0 R^3 \mathcal{G} \cdot \mathcal{H} $, and a steady force on a thin rod of radius $R$ and length $L$ proportional to $- \mu_0 R^2 L (\mathcal{G} \cdot \mathcal{H} - \tfrac{1}{2} (\mathcal{G} \cdot \hat o)(\mathcal{H} \cdot \hat o))$, where $\mu_0$ is the magnetic permeability. There is torque proportional to $\mu_0 R^2 L (\hat o \times \mathcal{H} ) (\hat o \cdot \mathcal{H} )$ on a thin rod which tends to align the rod direction of the magnetic field. The coefficients in the force and torque expressions are functions of the dimensionless ratio of the radius and the penetration depth of the magnetic field, $\beta R = \sqrt{\mu_0 \omega \kappa R^2}$, where $\kappa$ is the electrical conductivity. It is shown that the effect of particle interactions can be expressed as an anisotropic diffusion term in the equation for the particle number density. The diffusion coefficient is negative, and concentration fluctuations are amplified, in the plane perpendicular to the magnetic field.
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Materials Science

Data-Driven Estimation of the interfacial Dzyaloshinskii-Moriya Interaction with Machine Learning

Davi Rodrigues, Andrea Meo, Ali Hasan et al. (+8 more)

Machine learning offers powerful tools to support experimental techniques, particularly for extracting latent features from large datasets. In magnetic materials, accurately estimating the interfacial Dzyaloshinskii-Moriya interaction strength remains challenging, as existing experimental methods often rely on indirect measurements and can yield inconsistent results across techniques. Because this interaction is often extracted experimentally from bubble domain expansion, we investigate whether bubble textures alone contain sufficient and reliable information for data driven DMI inference. We therefore develop a compact convolutional neural network trained on a comprehensive micromagnetic dataset of magnetic bubble domains designed to emulate magneto optical Kerr effect imaging, including structural non uniformity, additive noise, and image pixelation. The proposed network demonstrates strong robustness against sample inhomogeneities, noise, and reduced spatial resolution. Furthermore, it exhibits reliable generalization by accurately predicting DMI values outside the trained interval. These results support the use of machine learning as a fast and quantitative tool to characterize magnetic textures with interfacial DMI.
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All authors Davi Rodrigues, Andrea Meo, Ali Hasan, Edoardo Piccolo, Adriano Di Pietro, Alessandro Magni, Marco Madami, Giovanni Finocchio, Mario Carpentieri, Michaela Kuepferling, Vito Puliafito

Materials Science · Cross-listed from physics.flu-dyn

Interplay between Temperature Oscillations and Melt Pool Dynamics in 3D Manufacturing Techniques

Stepan L. Lomaev, Georgii A. Gordeev, Marat A. Timirgazin et al. (+2 more)

The aim of this paper is coupling of temperature oscillations and melt pool dynamics experimentally observed in laser melting. The literature survey has shown that the developed explanations are mainly focused on the capillary and hydrodynamic aspects of the problem. As shown, complete analysis is only possible if the temperature oscillations are properly accounted for. Specifically, this effect is a governing mechanism that controls the melt pool dynamics via feedback coupling of heating, evaporation, capillarity and free-surface contraction. The present study suggests a physically consistent model validated on the detailed data of the time-resolved absorptance measured in [Phys. Rev. Appl. 10, 044061 (2018)]. An analytical equation is derived for oscillation spectra within this approach. It has been proved that the surface oscillations can be initiated without the keyhole effect. However, keyhole formation can cause additional modes to appear in the oscillation spectrum. The practical results include the formulas that are convenient for real-time monitoring of the surface temperature and characteristic flow velocity in the molten pool using the measured absorptance spectra. The impact of the temperature coefficient of surface tension on the maximal temperature, pool length, natural frequency of the free surface oscillations, and attenuation coefficient is thoroughly studied. All results are presented as closed-form formulas suitable for design of industrial laser systems.
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All authors Stepan L. Lomaev, Georgii A. Gordeev, Marat A. Timirgazin, Dinara R. Fattalova, Mikhail D. Krivilyov

Soft Condensed Matter · Cross-listed from physics.flu-dyn

Simulating the swimming motion of a flagellated bacterium in a microstructured bio-fluid

Arjun Sharma, Sabarish V. Narayanan, Sarah Hormozi et al. (+1 more)

We develop a numerical framework to simulate the locomotion of a flagellated bacterium with a spheroidal head (such as Escherichia coli) in biological fluids like mucus, which are entangled polymer solutions exhibiting elasto-viscoplastic (EVP) rheology and porous microstructure. To account for the scale disparity between the large bacterial head and the slender flagellar bundle, whose thickness is comparable to the pore size, we employ a two-fluid model in which the bundle directly drives the solvent and exchanges momentum with the polymer phase via drag proportional to their relative velocity. The numerical implementation combines a finite-difference discretization of the two-fluid equations with a slender-body theory (SBT) to model flagellar forcing. A key observation is that the coupled mass and momentum equations for these inertialess flows, together with SBT, are linear in the pressure and velocity fields and in the force distribution along the flagellar bundle. By treating the polymer stress as a body force, we decompose the flow field and hydrodynamic moments into three additive contributions: kinematic (motion), flagellar forcing, and polymer stress. This decomposition allows several components of the flow to be precomputed and enables the determination of swimming velocity via a resistivity formulation driven by polymer-induced forces, which greatly improves computational efficiency during transient calculations of the polymer stress and the resulting flow. We validate the method and use it to analyze how polymer microstructure and its interactions with the bacterial head and tail affect motility in complex biofluids.
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All authors Arjun Sharma, Sabarish V. Narayanan, Sarah Hormozi, Donald L. Koch

Soft Condensed Matter

The effects of ionic valency and size asymmetry on counterion adsorption

Or Ben Yaakov, Haim Diamant, Rudolf Podgornik et al. (+1 more)

We study the effect of asymmetry in solvent and ionic size on the equilibrium properties of multivalent ionic solutions near a charged surface. For a single ionic species in solution, we derive a generalized Grahame equation at the charged surface. For general size ratio between the ions and the solvent, we obtain analytical results for the concentration profiles as a function of the distance from the surface. For weak surface charge and small ion-to-solvent size ratio, the profile follows the classical Poisson-Boltzmann equation in dilute solution conditions. However, for high surface charge and large ionic size, the concentration profile saturates near the surface, leading to distinctive dependencies of the solution properties on the surface charge density and size asymmetry. Furthermore, the crossover between dilute and saturated regimes depends on the surface charge and ionic size asymmetry. We suggest that a solution containing multiple ionic species of different valencies and sizes stratifies close to the surface in the saturation regime. This leads to the formation of layers that are ordered according to the ions' valency-to-size ratio.
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All authors Or Ben Yaakov, Haim Diamant, Rudolf Podgornik, David Andelman

Strongly Correlated Electrons · Cross-listed from math-ph

The Full Set of KMS-States for Abelian Kitaev Models

Danilo Polo Ojito and Emil Prodan

We first prove that the subalgebra $\mathcal{C}$ generated by the vertex and face operators of an abelian Kitaev model is a $C^\ast$-diagonal of the UHF algebra $\mathcal{A}$ of quasilocal observables. This gives us access to the Weyl groupoid $\mathcal{G}_\mathcal{C}$ associated with the $C^\ast$-inclusion $\mathcal{C} \hookrightarrow \mathcal{A}$, which supplies a valuable presentation of $\mathcal{A}$ as a groupoid $C^\ast$-algebra where the dynamics of the model are generated by a groupoid 1-cocycle $c_H$. Making appeal to the notion of $(c_H,\beta)$-KMS measures for this groupoid, we identify the full set of KMS states of the model and prove its uniqueness for $\beta \in [0,\infty)$. Furthermore, we show that its limit at $\beta \rightarrow \infty$ exists and coincides with the unique frustration-free ground state of the model.
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Materials Science

Neural operator accelerated atomistic to continuum concurrent multiscale simulations of viscoelasticity

Tanvir Sohail, Burigede Liu and Swarnava Ghosh

We present a neural-operator-accelerated concurrent multiscale framework that couples atomistic simulations with continuum finite-element analysis for history-dependent materials, thereby making atomistic-continuum multiscale simulations of viscoelastic materials tractable. The approach replaces direct molecular dynamics (MD) evaluation of the constitutive response with a Recurrent Neural Operator (RNO) surrogate trained on atomistic simulations. The surrogate learns the strain-history-to-stress operator from molecular dynamics simulations and provides a discretization-independent approximation of the atomistic constitutive mapping, enabling efficient evaluation of stresses and latent internal variables at each quadrature point. The framework is implemented within an explicit finite-element solver, where the constitutive update reduces to inexpensive operator evaluations rather than repeated MD solves. Memory effects are represented through learned internal states, and transfer learning across temperature enables the surrogate to capture thermally dependent viscoelastic behavior. The method is assessed using polyurea through cyclic loading, Taylor impact, and plate impact simulations and compared with an experimentally calibrated viscoelastic polyurea model and a Johnson-Cook model. The neural-operator surrogate reproduces correct viscoelastic response while enabling atomistically informed dynamic simulations at scales that are not tractable with direct MD-FEM coupling.
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Superconductivity

Unified pressure and field response across distinct charge-order regimes in Ti-doped CsV$_3$Sb$_5$

P. Kràl, S.S. Islam, Andrea N. Capa Salinas et al. (+10 more)

Understanding the phase diagram of kagome superconductors from a microscopic perspective is crucial for clarifying the interplay between charge order and superconductivity. Ti-doped CsV$_{3}$Sb$_{5}$ exhibits a nonmonotonic temperature-doping phase diagram in which both $T_{\rm c}$ and the charge-order temperature initially decrease with doping, followed by a crossover from long-range to short-range charge order and a subsequent increase in $T_{\rm c}$. Here, we report a muon spin rotation ($\mu$SR) study of Ti-doped CsV$_{3}$Sb$_{5}$ at two representative compositions: underdoped (Ti$_{0.05}$-CVS) and optimally doped (Ti$_{0.22}$-CVS). Using zero-field, high-field, and high-pressure $\mu$SR, we find spontaneous time-reversal-symmetry (TRS) breaking in the normal state of both compositions, strongly enhanced by an applied magnetic field and associated with long-range and short-range charge-order correlations, respectively. In the superconducting state, both samples exhibit anisotropic nodeless pairing with low superfluid density. Hydrostatic pressure substantially enhances both $T_{\rm c}$ and the superfluid density (by $\sim$2.5), revealing a linear correlation between them and pointing to unconventional pairing. Above $\sim$1 GPa, a crossover from anisotropic to isotropic nodeless pairing is observed. Despite the different nature of charge order in the two doping regimes, the superconducting responses are remarkably similar, suggesting that the competition between superconductivity and charge order occurs on a local scale, largely independent of the long-range coherence of the charge-ordered state.
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All authors P. Kràl, S.S. Islam, Andrea N. Capa Salinas, J.N. Graham, O. Gerguri, A. Doll, J. Krieger, T.J. Hicken, G. Simutis, H. Luetkens, R. Khasanov, S.D. Wilson, Z. Guguchia

Superconductivity

Correlated charge order intertwined with time-reversal symmetry-breaking nodal superconductivity in the dual flat band kagome superconductor CeRu$_{3}$Si$_{2}$

O. Gerguri, P. Kràl, M. Spitaler et al. (+19 more)

Kagome materials provide a powerful platform for exploring how flat electronic bands promote symmetry-breaking quantum states, yet studies have so far focused mainly on kagome-derived $d$-electron flat bands. In this paper, we introduce CeRu$_{3}$Si$_{2}$, a kagome superconductor in which our first-principles calculations show the coexistence of Ru $d$-orbital kagome flat bands and heavy-fermion flat bands derived from Ce$^{4+}$ $4f$-states. X-ray diffraction reveals a dominant 1/2 charge order with a much weaker 1/3 component persisting up to room temperature. Theoretical calculations further highlight the correlated nature of these charge-order states. Deep within the charge-ordered state, magnetoresistance emerges below 80 K and strengthens further below 30 K. Zero-field muon spin-rotation measurements show no time-reversal symmetry (TRS) breaking in the normal state, in contrast to LaRu$_{3}$Si$_{2}$ and YRu$_{3}$Si$_{2}$. However, an applied magnetic field induces weak magnetism. Across the $A$Ru$_{3}$Si$_{2}$ family ($A$ = La, Y, and Ce), the superconducting transition temperature $T_{\rm c}$ scales linearly with the onset temperature of normal-state TRS breaking $T_{\rm {TRSB}}$ and the magnitude of the field-induced magnetic response, revealing a direct positive correlation between normal-state symmetry breaking and superconductivity. Furthermore, we identify that CeRu$_{3}$Si$_{2}$ is the first 132-type kagome compound to host nodal superconductivity together with spontaneous internal magnetic fields, providing clear evidence for intrinsic TRS breaking in the superconducting state. These results establish CeRu$_{3}$Si$_{2}$ as a unique platform where intertwined kagome $d$- and heavy fermion $f$-electron flat bands generate a rich hierarchy of electronic orders.
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All authors O. Gerguri, P. Kràl, M. Spitaler, M. Salamin, J.N. Graham, A. Doll, I. Biało, I. Plokhikh, J. Krieger, T.J. Hicken, J. Oppliger, L. Martinelli, A. Steppke, N. Shepelin, R. Khasanov, M.v. Zimmermann, B. Monserrat, H. Luetkens, J. Chang, F.O. von Rohr, Sun-Woo Kim, Z. Guguchia

Soft Condensed Matter

Shear-induced self-diffusivity in dilute suspensions with repulsive interactions

Anu V S Nath, Pijush Patra and Anubhab Roy

In a dilute non-Brownian suspension undergoing simple shear, pairwise hydrodynamic interactions are fore-aft symmetric at zero Reynolds number and produce no net cross-streamline displacement. A weak central repulsive force between particles breaks this symmetry, deflecting trajectories and generating irreversible transverse displacements that cumulatively yield a shear-induced self-diffusivity. We derive, via matched asymptotic expansions in the limit of weak repulsion, closed-form scaling laws for the gradient and vorticity components of this diffusivity. The gradient component exhibits a logarithmic enhancement relative to the vorticity component, a structural anisotropy that persists for all monotonically decaying repulsive potentials. The specific interaction enters only through integral functionals of the force profile weighted by hydrodynamic mobility functions, establishing that the scaling is universal across physically distinct mechanisms, such as electrical double-layer repulsion, steric interactions, or any other short-range central force. We validate the asymptotic predictions against full numerical trajectory integration for the representative case of electrostatic repulsion, modelled using the Gouy-Chapman description of the electrical double layer, and find excellent agreement in the expected regime.
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Materials Science

Spin waves and instabilities in the collinear four component antiferromagnetic materials

Pavel A. Andreev

The small amplitude perturbations of spins are considered in the four component antiferromagnetic materials with the equilibrium state of form up-up-down-down (uniaxial samples). Other configurations for the four component antiferromagnetic materials and two component antiferromagnetic materials are briefly considered for the comparison with main regime. Dispersion dependencies of two spin waves existing in the system are found if equilibrium spins are parallel to the anisotropy axis. Dispersion equation leading to a possibility of four spin waves is derived if equilibrium spins are perpendicular to the anisotropy axis. It is found that at least one solution has negative frequency square for all possible modules and signs of the anisotropy constants. Calculations are made for the one dimensional chain of classical spins in the approximation of the nearest neighbours interaction. Next, we also addressed the nearest neighbours interaction approximation in the limit of the continuous medium (for the Landau–Lifshitz–Gilbert equation). Mostly applied form of the Landau–Lifshitz–Gilbert equation goes beyond the nearest neighbours interaction approximation. The difference is described. Required assumptions are described.
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Mesoscale and Nanoscale Physics

Spin–valley–resolved tunneling through magnetic barriers in WSe$_2$

Rachid El Aitouni, Clarence Cortes, David Laroze et al. (+1 more)

We investigate the influence of a magnetic field on the electronic properties of WS$e_2$ with a focus on spin-orbit coupling, spin and valley polarization, and conductance. We solve the eigenvalue equation analytically and use the continuity equation to determine the transmission probability based on current densities. We calculate the conductance using Büttiker formula. Our numerical results indicate that transmission through the $K$ valley is more likely than through the $K'$ valley. For both valleys, the Klein tunneling effect is clearly observed. The conductance is affected by an increase in the magnetic field because it alters the energy levels of fermions via the Zeeman effect. These modifications enable the confinement of fermions within the barrier. Spin and valley polarization are also influenced by the magnetic field. As the field intensity increases, it steers the fermions and determines which channel can cross the barrier. This adds another tool of controlling fermions, paving the way for relevant applications in valleytronics and valley filtering for information storage.
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All authors Rachid El Aitouni, Clarence Cortes, David Laroze, Ahmed Jellal

Materials Science

Chemical Medium-Range Order Enables Stoichiometric Rigidity

Kejun Liu

Maxwell counting predicts an isostatic threshold at $\langle r\rangle = 2.4$ for covalent network glasses, but which structural correlations actually produce rigidity near this point is still unclear. In this work, we test four candidates: enthalpic stress, chemical defects, geometric interlocking, and medium-range order (MRO). We use a locally tree-like configuration model as a zero-MRO baseline and apply perturbations to test each candidate. We find that (i) enthalpic stress delays rigidity rather than enabling it; (ii) chemical defects require fractions ($\sim$40%) far above experimental values ($\sim$16% in GeSe$_2$); (iii) geometric linking density does not govern the threshold location, which is instead set by loop-induced redundancy; and (iv) only phenomenological MRO proxies recover rigidity at experimentally accessible strengths. Consequently, chalcogenide intermediate-phase data and amorphous SiO$_2$ ring statistics positively implicate chemical MRO, while DNA spatial networks independently rule out pure geometric entanglement. We conclude that rigidity near the Maxwell threshold requires chemistry-specific correlations beyond pure connectivity.
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Other Condensed Matter

Direct and inverse photoemission spectra from the screened multichannel Dyson equation

Pina Romaniello and J. Arjan Berger

We present the screened multichannel Dyson equation for the simulation of both direct and inverse photoemission spectra from first principles. The screened multichannel Dyson equation improves upon the standard multichannel Dyson equation by correctly including the screening of all particle-particle and electron-hole interactions due to the presence of the other electrons. Using the example of bulk silicon, we demonstrate that the screened multichannel Dyson equation can capture the main features of the direct and inverse photoemission spectra. In particular, it captures the correct position of the silicon plasmon satellite, unlike standard many-body approaches such as $GW$, which strongly overestimates the binding energy of this satellite. Finally, we show that also the standard multichannel Dyson equation and the second-Born approximation strongly overestimate the binding energy of the plasmon satellite, thus demonstrating the importance of properly screening all particle-particle and electron-hole interactions.
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Statistical Mechanics · Cross-listed from physics.med-ph

Deep brain microelectrode signal: $q$-statistical approach

Ana Luiza Souza Tavares, Henrique Santos Lima, Artur Pedro Martins Neto et al. (+2 more)

We characterize the amplitude statistics of intraoperative microelectrode recordings (MERs) obtained during deep brain stimulation (DBS) surgery in 46 patients with Parkinson's disease, using 184 recordings equally balanced between inside and outside the subthalamic nucleus (STN). The probability density of every recording is quantitatively well described by a $q$-Gaussian (grounded on a nonadditive entropic functional), $\rho(x) \propto [1 + \beta(q-1) x^2]^{-1/(q-1)}$, with $q > 1$ in all cases, reflecting persistent long-range temporal correlations inconsistent with Gaussian dynamics. Within the superstatistics framework, the slowly fluctuating local variance visible in the raw MER signals is a physical mechanism that directly generates the $q > 1$ form. Beyond individual fits, $q$ and $\beta$ collapse across all 184 recordings onto the single functional constraint $q = 3 - 1.85\,\beta^{-0.33}$ ($R \approx -0.91$), a reduction to one effective degree of freedom that is the quantitative hallmark of near-critical dynamics, previously identified in scale-free network growth and in acoustic precursors of material fracture. The index $q$ is statistically indistinguishable across the STN boundary ($\langle\bar{q}_\text{out}/\bar{q}_\text{in} \rangle = 1.03$), while the inverse-widthparameter shows a modest systematic difference ($\langle\bar{\beta}_\text{out}/\bar{\beta}_\text{in} \rangle = 1.18$). Since $q > 1$ is expected for any brain structure exhibiting long-range correlations, healthy or pathological, it is the tight $q(\beta)$ coupling, not $q > 1$ per se, that constitutes the candidate near-criticality signature of the parkinsonian cortico-basal-ganglia-thalamocortical loop.
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All authors Ana Luiza Souza Tavares, Henrique Santos Lima, Artur Pedro Martins Neto, Bruno Duarte Gomes, Constantino Tsallis

Strongly Correlated Electrons · Cross-listed from math-ph

Quantum Hall States response to toroidal geometry deformation

Bruno Mera, José M. Mourão, João P. Nunes et al. (+1 more)

In this paper, we apply techniques of geometric quantization to study the response of the integer and fractional quantum Hall effects to toroidal geometry deformation. The main method is that of using complex time Hamiltonian evolution to induce the geometry change and then the associated generalized coherent state transforms (gCST) to find the evolution of the Laughlin states. We consider two kinds of deformations. The first are flat toroidal deformations. Although Laughlin states for all flat toroidal geometries have been thoroughly studied before, we believe that our approach via the gCST is novel. It also serves as a testing ground to study the non-flat Kähler deformations. The Hamiltonians used in the flat deformations are quadratic in the generators of translations and therefore non periodic. The second kind of deformations involve nonflat Kähler toroidal deformations, generated by global, thus bi-periodic, Hamiltonians on the torus. The corresponding imaginary time flows are (elliptic curve modulus) $\tau$-preserving Mabuchi geodesics in the space of Kähler metrics on the torus, hitting a curvature singularity in finite imaginary time. By restricting to $S^1$-invariant deformations we find explicit analytic expressions for the evolution of the toroidal geometry and of the Laughlin states all the way to the singularity.
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All authors Bruno Mera, José M. Mourão, João P. Nunes, Carolina Paiva