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Physics Condensed Matter

cond-mat Watch Condensed Matter

Sunday 7 June

Materials Science

Chiral-Angle-Controlled Spin Splitting and Spin Transport in Nanotubes Rolled from d-wave Altermagnets

Ersoy Sasioglu, Tom. G. Saunderson, Börge Göbel et al. (+2 more)

Altermagnets combine compensated collinear magnetic order with momentum-dependent spin splitting in the electronic band structure. Here, we show that rolling a two-dimensional (2D) $d$-wave altermagnet into a nanotube converts this momentum dependence into chiral-angle-controlled one-dimensional (1D) spin splitting through dimensional projection. A minimal tight-binding model reveals a characteristic nodal–antinodal dependence on the chiral angle $\theta$, with the central circumferential subband exhibiting a $\cos(2\theta)$ scaling and the projected spin splitting vanishing for the nodal orientation and reversing sign between orthogonal antinodal orientations. First-principles calculations for V$_2$O and representative symmetric and Janus systems demonstrate that this nodal–antinodal selection rule persists despite curvature-induced structural asymmetry and magnetic moment imbalance. We further show that the projected electronic structure produces chiral-angle-controlled spin-polarized transport: antinodal nanotubes exhibit spin-polarized transmission, whereas the nodal nanotube remains conducting with identical spin-channel transmission. These results demonstrate how dimensional projection can translate the momentum-space spin splitting of a 2D altermagnet into geometrically controlled electronic and transport properties in nanotubes.
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All authors Ersoy Sasioglu, Tom. G. Saunderson, Börge Göbel, Ingrid Mertig, Samir Lounis

Disordered Systems and Neural Networks · Cross-listed from quant-ph

Quantum resource localizability transitions in deep thermalization

Xiaozhou Feng, Chang Liu, Zihan Cheng et al. (+2 more)

We investigate how quantum resource constraints affect deep thermalization, the emergence of universal local wavefunction distributions from partial measurements of a quantum many-body state. Quantum resources, such as non-stabilizerness (magic), coherence, asymmetry, imaginarity, and non-Gaussianity, are essential for quantum information processing, and constraints on their global abundance can reshape these emergent distributions. To address this question, we develop a unified framework for deep thermalization within general quantum resource theories (QRTs). Our central result is that QRTs fall into two classes: “smoothly localizable” (SL) QRTs, where the resource content of local post-measurement states changes continuously with the global resource density, set by the initial state and measurement basis, yielding continuously tunable wavefunction distributions; and “threshold localizable” (TL) QRTs, where the local resource content jumps discontinuously from minimal to near-maximal past a critical global resource threshold, producing a sharp transition between a resourceless, “deep-ergodicity breaking” distribution and a resourceful, maximally random one. We trace this SL-TL dichotomy to an information-theoretic mechanism, block sharpening: by viewing each QRT as coherence between blocks in Hilbert space, we show that the local resource content depends on the measurement's ability to collapse an initial superposition into a single resourceless block. Our theory is analytically tractable and quantitatively predicts the phase boundaries across all studied QRTs, which we validate with extensive numerical simulations. Finally, we highlight two consequences: a novel magic transition in zero-rate quantum error-correcting codes–previously believed to occur only at finite rates–and new implications for quantum resource certification protocols based on post-measurement state ensembles.
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All authors Xiaozhou Feng, Chang Liu, Zihan Cheng, Wen Wei Ho, Matteo Ippoliti

Statistical Mechanics

Wave Resistance for Stochastic Motion at Interfaces

Maxence Arutkin, Shlomi Reuveni and Elie Raphael

Wave resistance is the drag generated by the wave radiation that a source moving at a fluid interface sustains. Under stochastic trajectories, the mean drag is controlled by the ensemble-averaged surface profile built from the trajectory history. We show that the result is a finite resistance below the deterministic radiation threshold and a regularization of the singular response at the minimum phase velocity of the capillary-gravity waves. We derive explicit scaling laws for drifted Brownian trajectories, including a universal high-diffusivity decay. For drifted Lévy flight, we find the mean wave resistance in closed-form, extending wave-drag theory to non-Gaussian trajectories.
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Quantum Gases

Ultracold Amplification Proposal for Parity Violation in Chiral Molecules

Daniel Martínez-Gil, Pedro Bargueño and Salvador Miret-Artés

We propose a theoretical mechanism to indirectly detect the small parity-violating energy difference (PVED) between chiral enantiomers through a macroscopic enantiomeric excess observed in an ultracold gas. We consider that chiral molecules are formed resonantly via ultracold collisions of achiral diatomic molecules, with PVED inducing a slight asymmetry in the resonance energies of right- and left-handed configurations. After formation, chiral molecules evolve within a Bose-Einstein condensate (BEC), incorporating nonlinear interactions, tunneling between enantiomeric states, intrinsic PVED, and thermal conversion rates. These collective dynamics enable amplification of the microscopic bias into a global population imbalance. Using coupled rate equations, we show that, under realistic regimes, a complete enantiomeric excess can be achieved even for extremely small intrinsic asymmetries. We illustrate the model with concrete examples (HSOH, H$_2$Se$_2$, H$_2$Te$_2$), predicting observable enantiomeric excesses under plausible experimental conditions. We also consider non-PVED effects that could be amplified under the proposed mechanism, including electric and magnetic fields as well as thermal fluctuations, the latter being illustrated through the aforementioned molecular examples. Overall, our results suggest that ultracold physics could provide a new pathway to probe molecular parity violation, a fundamental weak effect that remains experimentally undetected.
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Disordered Systems and Neural Networks

Statistical Mechanics of Random Matrices

Isaac Pérez Castillo

These lecture notes are based on the lectures on Statistical Mechanics of Random Matrices delivered at the Spring College on the Physics of Complex Systems, held at the Abdus Salam International Centre for Theoretical Physics, Trieste, Italy, from 19 February to 15 March 2024. Their aim is to present a statistical-mechanics route to the spectral theory of sparse and diluted random matrices, with emphasis on cavity and replica methods, resolvent techniques, population dynamics, typical spectral densities, spectral-count fluctuations and large deviations, conditioned spectra, and non-Hermitian extensions. The written form of the notes has been deliberately expanded beyond the material actually covered during the lectures. This is partly because a set of lecture notes can afford a more systematic development than a sequence of blackboard lectures, and partly because several natural continuations of the material become clearer once the central methods have been introduced. Consequently, not every topic discussed here was presented during the College. The additional material is included to give a more coherent account of the subject and to indicate directions that, hopefully, can be covered in greater detail in future lectures or schools. Since these are lecture notes rather than a state-of-the-art review, the choice of topics is necessarily selective and is naturally tilted towards the author's own work and collaborations on this subject. I have nevertheless tried, within the limits of this format, to place the material in contact with the broader literature and to represent the surrounding state of the art as fairly as possible. Inevitably, some relevant contributions may be missing or treated too briefly; such omissions are unintentional and reflect the pedagogical scope of the notes rather than a judgement on their importance.
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Soft Condensed Matter

Discovering and decoding latent mean-field structure with variational autoencoders

Marco Biroli, Max Welling and Vincenzo Vitelli

Generative models are increasingly used to capture correlations in many-body systems, but the representations they learn remain largely opaque to physical interpretation. Here, we establish an intuitive criterion that quantifies the capacity of a variational autoencoder (VAE) to faithfully reconstruct the joint probability distribution of a many body system. In a nutshell, a bound on the VAE capacity is obtained by comparing the rate of the latent channel to the bipartite mutual information of the data. Using this bound, we show that the conditionally independent decoder of any successful VAE is structurally identical to a finite-size mean-field factorization. Hence, a successful reconstruction is direct evidence for a latent mean-field theory and the microscopic parameters of that theory can be read off the trained decoder. We validate these conclusions on a hierarchy of solvable models with scalar (Curie-Weiss), vector (Hopfield) and tensor (Maier-Saupe) order parameters, recovering the full Hopfield pattern matrix from equilibrium samples alone. We find that, when applied to Salamander retinal recordings, a two-latent VAE reproduces the population statistics with only two effective collective variables allowing us to recover the `stored patterns' of the neural population and write a generalized Hopfield model which correctly models the experimental data.
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Disordered Systems and Neural Networks

Dynamical cavity method for continuous-time complex systems on sparse random graphs

Fernando L. Metz and Isaac Pérez Castillo

Dynamical mean-field theory (DMFT) reduces dense high-dimensional disordered dynamics to a self-consistent effective stochastic process. For sparse and heterogeneous networks, however, local fields contain finitely many strong inputs, so the Gaussian closure mechanisms of dense DMFT need not apply. We develop a continuous-time cavity derivation of sparse-network DMFT at the level of path measures for stochastic dynamics with general pairwise interactions on sparse random graphs. The cavity equations are exact on trees and yield the finite-time thermodynamic description on locally tree-like graphs. They show explicitly how reciprocity changes dynamical closure: fully directed graphs recover the sparse directed path-probability equation, whereas reciprocal or bidirected edges require conditional path kernels driven by the imposed history of the receiving node. Ensemble averaging gives laws over path-probability messages, with barycenters and higher-message moments closing by multilinearity and independence of incoming branches. A causal discrete-time derivation yields the corresponding population-dynamics representation, distinguishing trajectory populations for directed graphs from conditional branch-law or finite-depth tree populations for reciprocal graphs. We also formulate finite-memory numerical closures and test them in an additive-input recurrent neural network specialization. Finally, high-connectivity limits are obtained as projections of the sparse path-measure theory, clarifying when dense drift, noise, and response channels reduce to standard low-dimensional DMFT and when path-level descriptions remain essential.
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Materials Science

Information Entropy Based Crystal Structure Prediction of Chemically Disordered Alloys via Graph Convolutional Neural Networks

Suman Chabri and Gautam Anand

The phase prediction of chemically disordered alloys poses a significant computational challenge due to the combinatorial complexity of such materials. The high-throughput compositional exploration of chemically disordered alloys, including high-entropy alloys, requires an approach to efficiently explore the potential energy landscape of such complex materials. Additionally, a metric to quantify the potential energy landscape explored for phase prediction of the compositions needs to be defined. We propose an information-theoretic approach to phase prediction in chemically disordered alloys in the present work. We demonstrate the applicability of alchemical Monte Carlo sampling using an efficient Graph Convolutional Neural Network-Based machine learning model. We additionally demonstrate the applicability and limitations of the Bond Disproportion Vector (BDV) as a low-computational-cost descriptor and benchmark it against the state-of-the-art Smooth Overlap of Atomic Positions (SOAP) descriptor. We show the applicability of an information entropy-based metric for the phase prediction of binary (CoNi, MoW, FeNi and TaW), ternary (CoCrNi, CrFeNi), quaternary (CoCrFeNi) and quinary ($\mathrm{Al_x(CoCrFeNi)_{1-x}}$) alloys. Information entropy-based phase prediction can be applicable in challenging cases where conventional approaches are not feasible.
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Mesoscale and Nanoscale Physics · Cross-listed from q-bio.BM

Protein Dynamics Beyond Structure Prediction

Juliette Griffié, Sviatlana Shashkova, Antonio Ciarlo et al. (+40 more)

The ability to predict protein three-dimensional structures from amino acid sequences is a landmark achievement in molecular biology, where recent deep learning approaches such as AlphaFold are the culmination of decades of work. Yet, the quantitative understanding of how protein sequences give rise to dynamic conformational changes and higher-order assemblies remains unsolved. Folding and conformational states are dynamic, stochastic processes, shaped by sequence, energy, co-translational constraints, chaperone machineries, and the physicochemical conditions of the cellular environment. Recent advances now position the field to move beyond static structural endpoints toward a mechanistic understanding of folding dynamics in living systems. Single-molecule techniques enable time-resolved observation of folding trajectories and intermediate states hitherto hidden by traditional structural biology approaches, while computational innovations and data-driven approaches offer new ways to integrate heterogeneous data across scales. In this Roadmap, we review the current conceptual landscape of protein folding, examine the experimental and theoretical gaps that remain, and discuss emerging strategies that integrate high-resolution measurements with multiscale modeling. We outline a roadmap toward a quantitative and predictive science of protein folding dynamics, conformational kinetics, and macromolecular self-assembly. Realizing this vision would transform our understanding of the dynamics of molecular self-organization, from the folding of individual polypeptides to the emergence of dynamic macromolecular complexes. This will enable rational control of folding and misfolding in health and disease, extend protein engineering principles beyond static structural design, and establish a mechanistic foundation for predictive and personalized interventions in proteostasis-related disorders.
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All authors Juliette Griffié, Sviatlana Shashkova, Antonio Ciarlo, Sreekanth K. Manikandan, Claes Andréasson, Malin Bäckström, Tristan Bereau, Hjalmar Brismar, Carlos Bustamante, Marta Carroni, Roberto Covino, Andreas Dahlin, Sebastian Deindl, Lucie Delemotte, Arne Elofsson, John Eriksson, Giovanna Fragneto, Anders Gunnarsson, Per Hammarström, Caroline Ingre, Christian Kaiser, Petronella Kettunen, Mark C. Leake, Benjamin Loos, Anna Månberg, Antonia S. J. S. Mey, Richard Neutze, Thomas Nyström, Karl Palmås, Charley Schaefer, Markus J. Tamás, Nicola Ticozzi, Tomás S. Pilvelic, Jacopo Sacquegno, B.M. Tijms, Gunnar von Heijne, Björn Wallner, Vitali Zhaunerchyk, Simon Olsson, Joana B. Pereira, Julia Fernandez-Rodriguez, Fredrik Westerlund, Giovanni Volpe

Superconductivity

Coexistence of High Temperature Superconductivity and Antiferromagnetic Order in a Cuprate with Multiple Hole Fermi Pockets

Xiangyu Luo, Yinghao Li, Hao Chen et al. (+23 more)

The intricate relationship between high temperature superconductivity and antiferromagnetic order in cuprates, and the fundamental origin of electron pairing remain open questions. By utilizing high-resolution laser-based spatially-resolved angle-resolved photoemission spectroscopy, we investigate the seven-layer $Bi_{2}Sr_{2}Ca_{6}Cu_{7}O_{18+\delta}$ (Bi2267) and identify a cuprate system that consists of multiple hole Fermi pockets. The observed Fermi pockets exhibit pronounced momentum-, temperature- and Fermi surface-dependent energy gaps. Crucially, high temperature superconductivity with a critical temperature ($T_{\mathrm{c}}$) of $\sim$75 K emerges in a system with multiple Fermi pockets and the presence of strong antiferromagnetic order and correlations. In particular, substantial electron pairing is observed along the Fermi pocket with an energy gap up to $\sim$42 meV in lightly-doped CuO$_{2}$ planes ($p\sim$0.05). These findings challenge the conventional understanding of the roles of the nodal and antinodal electronic states in driving high-temperature superconductivity. They show that superconductivity and antiferromagnetism can coexist in a cuprate with multiple Fermi pockets, offering further insights into the pairing mechanism in cuprate superconductors.
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All authors Xiangyu Luo, Yinghao Li, Hao Chen, Yiwen Chen, Jumin Shi, Taimin Miao, Bo Liang, Wenpei Zhu, Neng Cai, Xiaolin Ren, Yingjie Shu, Chaohui Yin, Jiuxiang Zhang, Chengtian Lin, Shenjin Zhang, Zhimin Wang, Fengfeng Zhang, Feng Yang, Qinjun Peng, Zuyan Xu, Guodong Liu, Xintong Li, Hanqing Mao, Tao Xiang, Lin Zhao, X. J. Zhou

Materials Science

Nonperturbative isotope effect on light-matter interaction in boron arsenide

Huan Wu

The interaction of light and matter under strong isotope disorder gives rise to unconventional physics that goes beyond the quantum perturbation theory. In boron arsenide, the large mass difference between the two stable boron isotopes presents a paradigmatic case where perturbation theory fails, yet a unified theoretical framework across the perturbative and nonperturbative regime has remained elusive. Here, we develop a nonperturbative approach to capture isotope-disorder effect in boron arsenide, which fundamentally alters light-matter interactions. We reveal that coherently mixed vibrations between two boron isotopes reshape the dielectric function in the nonperturbative regime. The nonperturbative isotope interactions dictate the properties of coupled surface phonon polaritons and near-field radiative heat transfer. Two-fold tuning of radiative heat flux is achieved by modulating the surface phonon polariton resonance via isotope engineering. This work establishes a unified framework connecting the perturbative and nonperturbative limits, enabling quantitative predictions across weak to strong disorder regime.
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Mesoscale and Nanoscale Physics

Novel 2D Altermagnetic Vanadium Oxide with a Buckled Lieb Structure

Tamer Taşk{\i}ran, Soheil Ershadrad, Biplab Sanyal et al. (+1 more)

Altermagnetism has recently emerged as a highly promising phase for spintronics, offering the combined advantages of both antiferromagnets and ferromagnets. Here, using a first-principles analysis based on density functional theory (DFT), we identify a monolayer V$_2$O crystal in a buckled Lieb lattice as a promising two-dimensional altermagnetic material. The structural and thermal stability of V$_2$O is verified through calculations of the crystal's formation energy, phonon structure, room-temperature ab initio molecular dynamics, and stiffness matrix. The system is found to exhibit auxetic behavior with a negative Poisson's ratio. Our calculations indicate an antiferromagnetic ground state with a local magnetic moment of $2.79\,\mu_{\mathrm{B}}$ per V atom and a magnetocrystalline anisotropy that favors an out-of-plane easy axis. The electronic structure exhibits a momentum-dependent spin splitting of 1.2 eV, which is a characteristic of altermagnets. Inclusion of spin-orbit coupling breaks the symmetry of the quadratic band crossing near the Fermi level, resulting in a large Berry curvature and significant intrinsic spin Hall conductivity around $40\,(\hbar/e)\,\mathrm{S\,cm^{-1}}$. The results demonstrate that monolayer V$_2$O serves as a robust room-temperature altermagnetic platform, exhibiting magnetic anisotropy and spin-dependent transport responses.
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All authors Tamer Taşk{\i}ran, Soheil Ershadrad, Biplab Sanyal, Cüneyt Şahin

Strongly Correlated Electrons

Inhomogeneous Coulomb Models Without Defects are Sick: Domain Wall Energies Scaling as Volume (not Boundary Area)

Garry Goldstein

In this work we show that coulomb models, ones that obey a $\nabla\cdot\left\langle \mathbf{B}\right\rangle =0$ divergence free constraint - for $\left\langle \mathbf{B}\right\rangle $ being some coarse grained variables related to the microscopic degrees of freedom of the lattice system - are sick without the inclusion of defects with $\nabla\cdot\mathbf{B}\neq0$. We show that for generic boundaries (ones where the fluxes of the pseudo-magnetic fields on the boundary do not cancel: $\left(\left\langle \mathbf{B}_{R}\right\rangle -\left\langle \mathbf{B}_{L}\right\rangle \right)\cdot\mathbf{n}\neq0$ - here $\mathbf{n}$ is the unit normal and $\left\langle \mathbf{B}_{R/L}\right\rangle $ are the two ground state pseudo-magnetic fields on either side of the domain wall) without the inclusion of defects, sharp domain walls (on the order of the width of a unit cell) between different phases of the system cost energy proportional to system size (not boundary area). We present several different examples of this phenomena in the square lattice six vertex model, in quantum dimers and in classical spin ice in the presence of magnetic fields. We also show by example that the condition $\left(\left\langle \mathbf{B}_{R}\right\rangle -\left\langle \mathbf{B}_{L}\right\rangle \right)\cdot\mathbf{n}=0$ is a necessary but not sufficient condition for the boundaries to be compatible - that is domain wall energy to scale with domain wall area and not system size. To further present the importance of boundary conditions in Coulomb systems we show that system boundaries, even ones that satisfy $\int_{\partial V}\mathbf{B}\cdot\mathbf{n}=0$, have thermodynamic consequences - that is there is a cost, extensive in system size, to the Helmholtz free energy.
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Materials Science

Divergent Coherent Phonon Responses Across the Metal-Insulator Crossover

Felix Hoff, Timo Veslin, Tim Bartsch et al. (+3 more)

Ultrafast laser control of material properties hinges on understanding light-matter interactions. We use two experimentally accessible response functions, laser fluence induced phonon softening and the amplitude of coherent reflectance oscillations, to compare how strongly different materials respond to ultrafast photoexcitation. Comparing a diverse set of materials, we find that only a narrow class, including Sb, GeTe, and Bi2Te3, shows exceptional responses such as pronounced phonon softening and a giant increase of reflectance oscillations with increasing fluence. These response functions peak in an intermediate conductivity regime of about 102 - 104 S/cm, at the crossover between localized and delocalized electronic states. The corresponding class of solids also shows other unconventional properties including high dielectric constants, enhanced Born effective charges, coordination numbers exceeding the 8-N rule and uncommon bond rupture. This suggests that these materials employ a unique bonding mechanism, coined metavalent bonding. Frozen-phonon DFT calculations show that the strong fluence dependence arises from Peierls-like instabilities, leading to large deformation potentials and anharmonic double-well potentials. These findings identify metavalent bonding as a design principle for enhanced coherent phonon control and provide a quantitative framework for identifying materials with exceptional ultrafast responses.
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All authors Felix Hoff, Timo Veslin, Tim Bartsch, Carl-Friedrich Schön, Dante M. Kennes, Matthias Wuttig

Statistical Mechanics · Cross-listed from quant-ph

Hidden Conformal Boundary Data in Finite-Temperature Stabilizer Entropy

Reyhaneh Khasseh and M. A. Rajabpour

We study the finite-temperature stabilizer Rényi entropy of the open critical quantum spin chains. At Rényi index one half, this observable probes the distribution of thermal Pauli-string expectation values and can be written as a sum over absolute values of all square minors of a finite-temperature correlation matrix for the transverse-field Ising chain. We show that this exponentially large sum is exactly reducible to a single Pfaffian. The Pfaffian representation reveals a block Toeplitz–Hankel structure and allows us to extract the large-size scaling in several thermal regimes. In the crossover window where the inverse temperature is proportional to the system size, the stabilizer entropy factorizes into a saturated extensive contribution and a universal finite-size scaling function. We find that this scaling function is a level-eight eta quotient, rather than the ordinary free-boundary Majorana thermal factor. The deviation is exponentially hidden at low temperature but controls the high-temperature crossover, where it gives a Cardy-like asymptotic for the Pauli-string expectation-weight spectrum. These results show that finite-temperature stabilizer entropy reveals hidden defect-like conformal data invisible to ordinary thermodynamic probes.
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Statistical Mechanics · Cross-listed from quant-ph

Another Legacy of Andrzej Kossakowski: A Self-Contained Derivation of the GKLS Equation

Gen Kimura

This note is written for the special issue of OSID dedicated to the 50th anniversary of the Gorini–Kossakowski–Lindblad–Sudarshan equation. Its purpose is not to give a comprehensive historical review, but rather to reconstruct, in a self-contained way, one logical route leading to the GKLS generator. The emphasis is placed on Kossakowski's structural insight: the combination of Markovianity, complete positivity, trace preservation, and the infinitesimal structure of quantum dynamical semigroups naturally leads to the celebrated form of the generator. I also include a few personal recollections of Andrzej Kossakowski, under whose guidance I spent one year as a postdoctoral researcher in 2003–2004.
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Materials Science

V-Doped Niobate Nanosheets for Enhanced Photocatalytic Activity

M. Tuğrul Avcu and Uğur Ünal

V-doped [Ca$_{2}$Nb$_{3-x}$V$_{x}$O$_{10}$]$^{-}$ (x = 0, 0.15, 0.3, 0.6, 0.75) nanosheets were produced by solid state reaction followed by protonation and exfoliation by tetrabutylammonium ions. 2D nanosheets have improved photocatalytic activity due to their small thickness that reduces electron-hole recombination, larger surface area that increases photocatalytic sites, and decreased band gap from added V. V-doping has caused the wide band gap of 3.54 eV of undoped nanosheets to decrease to 2.60-2.88 eV range. 10 vol% methanol was used as a hole scavenger in the hydrogen evolution reactions, and 3 wt% Pt was deposited on nanosheets as a co-catalyst. Under a full-spectrum Xe light, [Ca$_{2}$Nb$_{2.7}$V$_{0.3}$O$_{10}$]$^{-}$ has produced 4.7 times the H$_{2}$ yield as undoped nanosheets with a 11.3 mmol/g/h production rate, [Ca$_{2}$Nb$_{2.7}$V$_{0.3}$O$_{10}$]$^{-}$ with Pt co-catalyst has produced 2.9 times the H$_{2}$ yield as undoped Pt-loaded nanosheets.
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Strongly Correlated Electrons

Microscopic universal theory of symmetry-enriched topological quantum spin liquids

Yingcheng Li and Liujun Zou

An ultimate theory of a phase of matter should describe all its universal properties via quantities that are measurable numerically and experimentally. In this work, we present a microscopic universal theory of symmetry-enriched topological quantum spin liquids (TQSLs) in two spatial dimensions, which directly utilizes microscopically measurable quantities to describe the universal properties. This theory applies to generic TQSLs, which can be Abelian or non-Abelian, chiral or non-chiral. The symmetries are also general, which can include both internal and lattice symmetries, unitary and anti-unitary symmetries, and discrete and continuous symmetries. There can be spin-orbit coupling, the microscopic degrees of freedom may transform linearly or projectively under the symmetries, and the symmetries can permute anyons. The input of the theory is some microscopic states with anyons, operators that control the dynamics of anyons, and symmetry actions in the TQSL, and its output is a set of data characterizing the universal properties, whose underlying mathematical structure is a generalization of category theory. Based on this theory, we find an explicit bijective map between the universal data characterizing a TQSL with a symmetry described by a group $G$, where the symmetry actions may include both lattice and internal symmetries, and the corresponding universal data for a TQSL with only an internal symmetry group $G$, and thus establish a precise crystalline equivalence principle. We demonstrate our theory in symmetry-enriched TQSLs realized on quantum processors based on superconducting qubits, trapped ions, and Rydberg atoms, and in each example we verify the Lieb-Schultz-Mattis anomaly matching condition. Our theory provides a solid basis for identifying and manipulating symmetry-enriched TQSLs, which further paves the way for fault-tolerant quantum computation based on these systems.
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Materials Science

Dimensionality-Driven Charge Stabilization of Group-IV Color Centers in Diamond Ultrathin Films

Jijun Huang, Bing Huang and Song Li

Neutral group-IV vacancy (XV, X = Si, Ge, Sn, and Pb) centers in diamond are emerging solid-state spin-photon interfaces because of their favorable spin coherence and inversion symmetry-protected optical transitions. However, stabilizing their neutral charge state typically requires stringent Fermi-level engineering in high purity boron-doped diamond, which poses significant materials-growth challenges. Here, we demonstrate that dimensional confinement in diamane provides an alternative route to charge-state stabilization without intentional doping. Using first-principles calculations, we show that quantum confinement and surface termination cooperatively tune the host band gap and shift the occupied defect states upward from the valence-band edge, thereby enlarging the thermodynamic stability window of the neutral charge state and suppressing valence-band assisted excitation pathways. We further reveal that the thickness and surface termination of diamane enable systematic tuning of the electronic structure, zero-field splitting, and spin-orbit coupling of XV centers while largely preserving their optical transition energies. Among the structures considered, hydrogenated diamane offers the most favorable balance between charge-state stability and magneto-optical performance. More broadly, our findings establish dimensional confinement as a general strategy for engineering the charge, optical, and spin properties of solid-state quantum defects.
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Soft Condensed Matter

On the correlation lengths of confined spheres in a cylindrical pore

Ana M. Montero

We investigate the structural correlations of hard spheres confined within a narrow cylindrical pore in the quasi-one-dimensional regime, where interactions are restricted to nearest neighbors. Using a Laplace-space formulation of the radial distribution function (RDF), we determine the correlation lengths and oscillation frequencies associated with its long-distance decay. In addition to the global RDF, we analyze transverse-resolved RDFs that account for the positions of particle pairs across the pore cross section. While these observables are associated with the same underlying pole spectrum, their residues depend on the transverse configuration and can vanish due to symmetry. As a result, different particle-pair configurations may be governed by different leading poles and display different correlation lengths and oscillation frequencies. In particular, the global RDF does not always reflect the longest-ranged correlations found in transverse-resolved observables. We examine how this behavior depends on density and confinement. In the strong-confinement limit, the system approaches the Tonks-gas behavior at finite pressure, and the differences between the RDFs disappear.
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Soft Condensed Matter

Shear Banding in Amorphous Solids as a Nonlinear Screened Soft Mode Instability

Yang Fu, Yuliang Jin, Avanish Kumar et al. (+1 more)

Shear banding is a well-known and widespread instability in strained solids: under external strain, the deformation localizes along a line in two dimensions or a plane in three dimensions. Developing a proper theoretical description of this phenomenon is key to understanding mechanical failure in solid materials. Very recently, a nonlinear theory extending classical elasticity to include plastic deformations as topological charges was proposed, offering detailed predictions on the nature and consequences of the shear-banding instability. The theory derives a Hessian operator whose lowest eigenvalue vanishes at the onset of instability, and the corresponding critical eigenmode describes the displacement field across the shear band. The resulting soft mode possesses the selected localization scale and subsequently saturates into a finite-width shear band. The aim of this Letter is to examine this theory numerically, establishing the role of topological screening and nonlinear instability as the mechanisms governing shear banding during athermal quasistatic deformation. We show that the displacement profile around the shear band is directly determined by the screening parameter and the nonlinear coefficient, thereby quantitatively verifying the theoretical predictions. Our results demonstrate that shear banding differs fundamentally from fracture: it arises from a nonlinear instability of an elastic field screened by plastic deformations. This establishes topological screening as the essential mechanism governing shear banding in amorphous solids.
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All authors Yang Fu, Yuliang Jin, Avanish Kumar, Itamar Procaccia

Mesoscale and Nanoscale Physics

Topological bound states in the continuum with controllable multiplicity

Ya-Ping Lou and Wei Jia

Bound states in the continuum (BICs) are spatially localized states embedded in the continuous spectrum without hybridizing with extended bulk modes. Recent advances in topological band theory have greatly enriched the understanding of BICs, which gives rise to boundary-localized topological BICs with extremely high robustness against disorders. However, there remains a challenge in realizing corner-localized topological BICs in a three-dimensional system due to the absence of both realistic theoretical models and effective topological characterization schemes. In particular, how to engineer a controllable number of corner-localized topological BIC is still an open question. Here, we propose that the corner-localized topological BICs can emerge in a class of generalized breathing pyrochlore lattice with general inter-cell hoppings. We further show that the number of BICs at each corner can be arbitrarily adjusted by changing the parameters of inter-cell hoppings. Remarkably, although these corner-localized topological BICs are intertwined with a substantial number of bulk modes, we can accurately characterize them through the polarized topological charges, which are nodal points with topological properties in Brillouin zone and are measurable in experiments. We also reveal three types of topological phase transitions of corner-localized BICs, which are associated with the different ways of closing the bulk energy gap and can be intuitively captured by the polarized topological charges. This work not only promotes the theoretical research of corner-localized topological BICs, but also opens an avenue for their experimental observation in the future.
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Statistical Mechanics

What Is a Pattern in Statistical Mechanics? Formalizing Structure and Patterns in One-Dimensional Spin Lattice Models with Computational Mechanics

Omar Aguilar

This work formalizes the notions of structure and pattern for three distinct one-dimensional spin-lattice models (finite-range Ising, solid-on-solid, and three-body), using information-theoretic and computation-theoretic methods. We begin by presenting a novel derivation of the Boltzmann distribution for finite one-dimensional spin configurations embedded in infinite ones. We next recast this distribution as a stochastic process, thereby enabling us to analyze each spin-lattice model within the theory of computational mechanics. In this framework, the process's structure is quantified by excess entropy (predictable information) and statistical complexity (stored information), and the process's structure-generating mechanism is specified by its epsilon-machine. To assess compatibility with statistical mechanics, we compare the configurations jointly determined by the information measures and epsilon-machines to typical configurations drawn from the Boltzmann distribution, and we find agreement. We also include a self-contained primer on computational mechanics and provide code implementing the information measures and spin-model distributions.
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Superconductivity

First-Principles Investigation of Electron–Phonon Coupling and Intrinsic Two-Gap Superconductivity in Hexagonal BAs3 Monolayer

Jakkapat Seeyangnok and Udomsilp Pinsook

Two-dimensional superconductors with multiband electronic structures provide an ideal platform for exploring anisotropic and multigap superconductivity in the reduced-dimensionality limit. Here, we investigate the structural, electronic, vibrational, and superconducting properties of a hexagonal BAs$_3$ monolayer using first-principles calculations combined with density functional perturbation theory and fully anisotropic Migdal–Eliashberg theory. The optimized structure is found to be dynamically and thermally stable, as confirmed by phonon calculations and ab initio molecular dynamics simulations. Electronic structure calculations reveal an intrinsic metallic state with multiple bands crossing the Fermi level and several disconnected Fermi-surface sheets derived primarily from hybridized B-$p$ and As-$p$ orbitals. The electron–phonon interaction is dominated by low-frequency As-derived phonon modes, yielding a total electron–phonon coupling constant of $\lambda=0.75$. Solving the anisotropic Eliashberg equations predicts a superconducting critical temperature of $T_c=3.4$ K. The momentum-resolved superconducting gap exhibits a pronounced two-gap character with gap magnitudes of $\Delta_1=0.75$ meV and $\Delta_2=0.51$ meV at $T=1$ K. The superconducting gaps remain finite over the entire Fermi surface, demonstrating a fully gapped nodeless superconducting state. Analysis of the momentum-dependent electron–phonon coupling reveals that the two-gap superconductivity originates from sheet-dependent pairing interactions associated with distinct Fermi-surface sheets. Our results establish monolayer BAs$_3$ as an intrinsic anisotropic two-gap superconductor and expand the growing family of boron-based two-dimensional superconductors.
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Materials Science

First-Principles Insights into Surface and Ligand Effects in Stoichiometric HgTe Quantum Dots

Raagya Arora, Patrick J. Lohr, Dibyajyoti Ghosh et al. (+2 more)

HgTe quantum dots are promising mid-infrared nanomaterials owing to their exceptional bandgap tunability, yet their electronic structure is strongly influenced by surface coordination and ligand passivation at ultrasmall sizes. Here, we employ atomistic simulations to systematically investigate stoichiometric HgTe nanoclusters with sizes 0.86 to 1.85 nm. The in silico exploration uncovers a transition from confinement-dominated electronic structures with delocalized frontier states in small self-passivated clusters to surface influenced characteristics in larger nanoclusters. Increased coordination and bond-length inhomogeneity in the larger nanoclusters generate localized near-gap states centered on undercoordinated surface atoms. At intermediate sizes, the band edge states become spatially separated on different regions of the cluster without forming deep gap states, marking the onset of surface induced electronic asymmetry. In larger clusters (1.8 nm), common neutral ligands like amines, thiols, phosphines, and alcohols effectively eliminate surface-derived localized states by restoring local coordination and altering the band edge electronic structure through ligand surface hybridization. The sensitivity of the bandgap to ligand identity and binding site underscores the interplay between surface coordination and ligand chemistry in shaping the electronic structure of these nanoclusters. These insights provide an atomistic understanding of size-dependent electronic structures in ultrasmall HgTe clusters. The study further establishes neutral ligands as powerful chemical handles for engineering frontier electronic states relevant to infrared optoelectronic functionality.
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All authors Raagya Arora, Patrick J. Lohr, Dibyajyoti Ghosh, Jennifer Hollingsworth, Sergei Tretiak

Materials Science

Thermal Processing Limits in Oxide-Channel Ferroelectric Field Effect Transistors

Lance Fernandes, Yu-Hsin Kuo, Chengyang Zhang et al. (+15 more)

In this work, we report a systematic study of the impact of high-temperature post-capping thermal annealing on the memory characteristics of Oxide-semiconductor channel ferroelectric field-effect transistors (OS-FeFETs). Using an identical engineered ferroelectric gate stack 8nm Hf0.5Zr0.5O2 (HZO) / 3 nm Al2O3 / 8 nm HZO (8/3/8) and a hybrid capping layer (3 nm HfO2 + 3 nm Al2O3), 10 percent Ga doped InO (IGO) channel and 4 percent W doped InO (IWO) channel FeFETs remain functional after annealing at temperatures up to 650 C for durations of up to 30 min and 10 min, respectively; further annealing results in irreversible loss of conduction and device failure. Detailed electrical analysis reveals that the MW enhancement originates from a preferential positive shift in the erased-state threshold voltage, while the programmed-state threshold voltage remains comparatively stable. Grazing-incidence X-ray diffraction measurements further indicate structural evolution in the IWO and IGO oxide channels with increasing annealing temperature, supporting the observed electrical trends.
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All authors Lance Fernandes, Yu-Hsin Kuo, Chengyang Zhang, Priyankka Ravikumar, Ranie Jeyakumar, Dyutimoy Chakraborty, Jiayi Chen, Taeyoung Song, Kai Ni, Woohyun Hwang, Kwangyou Seo, Suhwan Lim, Wanki Kim, Daewon Ha, Julia Medvedeva, Suman Datta, Shimeng Yu, Asif Khan

Saturday 6 June

Soft Condensed Matter

Kinematic Inconsistencies and Initial-Value Boundary Paradoxes in Rate-Dependent Viscoelastic Yield Stress Models

Lalit Kumar

We present a rigorous analysis of the mathematical boundaries and kinematic consistency of a recently proposed rate-dependent relaxation time framework intended to unify pre- and post-yield dynamics in yield-stress fluids. By evaluating the governing constitutive equations under an idealized transient creep protocol from a state of physical rest, we show that the model encounters an unavoidable boundary paradox. To avoid predicting perfectly rigid solid behavior or falling into a division-by-zero mathematical singularity under a constant applied stress below the yield threshold ($\sigma \le \sigma_y$), the framework requires an unphysical, instantaneous velocity or strain-rate step at $t = 0^+$. We show that assuming a non-zero initial strain rate explicitly violates momentum conservation and fluid inertia. Consequently, the framework preserves the piecewise, discontinuous drawbacks of classic viscoplastic models.
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Statistical Mechanics

Quantum Otto and Carnot Cycles via Skew Ising Model

Neda Valizadeh, Nayyere Einali Saghavaz, Zahra Ebadi et al. (+1 more)

We investigate the thermodynamic performance of quantum heat engines and refrigerators based on a two-spin system subject to a skew magnetic field. The working substance is described by an interacting spin model that incorporates both spin–spin coupling and anisotropy induced by a tilted magnetic field. We analyze and compare quantum Carnot and Otto cycles, showing that the Carnot cycle exhibits a universal, entropy-driven behavior with smooth phase boundaries, while the Otto cycle displays a much richer structure governed by the interplay between the energy spectrum and nonequilibrium population differences. In particular, we identify a crossover in both efficiency and coefficient of performance as a function of the interaction strength, which arises from the competition between the interaction energy scale and the magnetic field. We further demonstrate that the skew angle induces state hybridization, modifying both the energy levels and occupation probabilities. Our results highlight that interactions and anisotropy, when properly tuned, can enhance thermodynamic performance, and emphasize the importance of multi-level effects in the design of quantum thermal machines.
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All authors Neda Valizadeh, Nayyere Einali Saghavaz, Zahra Ebadi, Hosein Mohammadzadeh

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

All-electron Dynamical Bethe-Salpeter Equation for Extended Systems with Atom-centered Orbital Basis

Ruiyi Zhou, Songrui Liu, Jianhang Xu et al. (+2 more)

Solving Bethe-Salpeter equation (BSE) for the two-particle Green's function is the most widely used approach for taking into account the particle-hole (exciton) interaction in electronic excitation in the context of the many-body theory based on Green's function. In BSE calculations, the static approximation to the screened Coulomb interaction kernel is commonly employed. However, when the excitonic character is significant as typically indicated by a large exciton binding energy, dynamical screening effects become non-negligible, rendering the static approximation questionable. Because of the large computational cost due to the dense Brillouin zone integration necessary for convergence, solving the dynamical BSE for extended systems remains a significant challenge, especially when combined with GW calculation for the calculation of quasi-particle energies. In this work, we formulate the plane-wave based effective dielectric function method [Zhang, et al., Phys. Rev. B 107, 235205 (2023)] for the dynamical BSE calculation using atom-centered orbitals as basis functions. We implement this approach in our recently developed all-electron numerical atom-centered orbital (NAO) implementation of BSE@GW [Zhou, et. al. J. Chem. Theory Comput. 21, 291 (2025)] for extended systems. We validate our all-electron NAO-based implementation of the dynamical BSE method, and we then discuss its realistic application to molecular crystal of naphthalene by performing the dynamical BSE@G0W0 calculation.
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All authors Ruiyi Zhou, Songrui Liu, Jianhang Xu, Yi Yao, Yosuke Kanai

Statistical Mechanics

A spectral model of power-law decay in natural and engineered systems

Balázs Sándor, Márk Honti and Henrique Santos Lima

We present a first-principles spectral mechanism for the emergence of nonextensive $q$-exponential dilution and power-law relaxation in non-ideal transport systems. By modeling an incompletely mixed reactor as a layered diffusion matrix with an absorbing boundary, we demonstrate that macroscopic power-law tails depend on the geometric interaction between the initial tracer placement and the domain's boundary configuration. For a one-dimensional system, an asymmetric, volumetrically distributed initial concentration profile projects onto the low-wavenumber eigenmodes, generating an emergent Gamma distribution of relaxation rates; at an infinitesimal boundary layer thickness ($\Delta z \to 0$), this profile yields the nonextensive $q$-exponential decay function exactly across the entire temporal domain with $q = 5/3$. Extended to $d$ dimensions under a highly localized, boundary-adjacent singular initial condition, the resulting scaling exponents and corresponding $q$ values depend explicitly on the spatial configuration of the absorbing boundaries. However, in the one-dimensional limit ($d=1$), these distinct initial states and boundary formulations intersect, rendering the $q=5/3$ exponent geometrically invariant. Our approach establishes a clear connection between linear diffusion transport and nonextensive statistical mechanics, showing how heavy-tailed transport can be derived from boundary geometry and spectral dimensionality.
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