Strongly Correlated Electrons · Cross-listed from quant-ph
All-Electric Quantum State Transfer via Spin-Orbit Phase Matching
Madhumita Sarkar, Roopayan Ghosh, Charles G. Smith et al. (+2 more)
Semiconductor hole-
spin qubits offer a promising route to
quantum computation due to their weak hyperfine interaction, and strong intrinsic
spin-orbit coupling enabling electric control of
qubits. Scalable architectures, however, require coherent long-distance
quantum state transfer, which is hindered in these systems by
spin-orbit induced anisotropic exchange. Here we show that this limitation can be overcome by using an all-electric control protocol. By tuning the electric field strength, we identify discrete
spin-orbit phase-matching conditions that restore near-perfect state transfer, independent of the rotation axis. Complementarily, controlling the electric field direction aligns the
spin-orbit axis, suppressing excitation non-conserving processes and enabling robust transfer without fine tuning. Our results establish that electrical control of
spin-orbit phases through either magnitude tuning or axis
alignment as a practical route for robust
quantum information transport in hole-
spin quantum dot arrays.
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All authors Madhumita Sarkar, Roopayan Ghosh, Charles G. Smith, Maksym Myronov, Sougato Bose
Strongly Correlated Electrons
Corner Charge Fluctuations in Higher Dimensions
Xiao-Chuan Wu, Pok Man Tam, Xuyang Liang et al. (+4 more)
Measuring charge fluctuations within a subregion provides a powerful probe of
quantum many-body systems. In two spatial dimensions, the shape dependence of the dimensionless corner contribution encodes universal data of
quantum critical points and reveals observables of
quantum geometry in various
quantum phases. Here, we systematically extend this framework to higher dimensions. In three dimensions, we derive the universal angle dependence associated with trihedral corners of a generic parallelepiped and
benchmark the predictions against Monte Carlo simulations of
lattice models at the O(3)
quantum critical point. We further identify a wedge-corner contribution that directly probes the
quantum metric, supported by numerical results for a
lattice Weyl semimetal model. More generally, we obtain angle functions for polyhedral corners of arbitrary parallelotopes in general dimensions and clarify the scaling of the corner contribution across phases of matter. While
insulators and conformal critical points exhibit similar behavior across dimensions, metals display a characteristic even-odd dimensional effect.
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All authors Xiao-Chuan Wu, Pok Man Tam, Xuyang Liang, Zenan Liu, Dao-Xin Yao, Zheng Yan, Shinsei Ryu
Quantum Gases · Cross-listed from quant-ph
Universal Spin Squeezing Dynamical Phase Transitions across Lattice Geometries, Dimensions, and Microscopic Couplings
Arman Duha and Thomas Bilitewski
Recent work has identified a dynamical squeezing phase transition in power-law interacting
bilayer XXZ
spin models, separating a fully collective phase with Heisenberg-limited squeezing from a partially-collective phase with universal critical scaling. Here we test and establish the universality of this transition along two qualitatively different microscopic axes:
lattice geometry, by studying square, triangular, and honeycomb $2\mathrm{D}$
bilayers as well as $1\mathrm{D}$ ladders, and a
symmetry-preserving rescaling $\lambda$ of the interlayer couplings relative to the intralayer ones. Combining a Bogoliubov instability analysis with discrete truncated Wigner simulations, we find that the transition persists across all four
lattice geometries and over a wide range of $\lambda$ with critical exponents consistent within error, providing strong evidence for a genuine non-
equilibrium universality class. The Bogoliubov theory recovers the previously identified scaling $a_Z^* \propto L$ in the long-range interacting regime $\alpha < d+2$, and yields an analytical scaling $a_Z^* \propto L^{2/(\alpha-d)}$ for the critical aspect ratio with system size for $\alpha>d+2$, with $\alpha$ the power-law exponent in dimension $d$. This uncovers a previously unrecognized sub-linear regime for short-range interactions. By tuning $\lambda$ we vary the interlayer coupling strength at fixed layer spacing, demonstrating that the dynamical transition can be driven purely through interaction engineering without modifying the underlying geometry. These findings provide a versatile route toward controlling
entanglement generation in Rydberg-array, polar molecule, and trapped-ion platforms with applications in
quantum sensing and simulation.
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Strongly Correlated Electrons · Cross-listed from hep-th
A Twist on Scattering from Defect Anomalies
Andrea Antinucci, Christian Copetti, Giovanni Galati et al. (+1 more)
In the presence of extended defects, familiar incoming particles can scatter into exotic outgoing states created by twist operators. We show that one possible mechanism driving these "categorical scattering" processes is the presence of localized 't Hooft anomalies on the defect's worldvolume. Defect anomalies trap non-trivial charges at junctions between the
symmetry lines and the interface, opening new transmission channels that would naively appear to violate selection rules. After outlining the general mechanism, we investigate several concrete examples with defects, interfaces, and boundaries. For models of massless
chiral fermions already studied in the literature, we show that the emergence of twist operators can be understood as a consequence of defect anomalies. We then introduce new massive integrable theories in which a similar phenomenon occurs, and we explicitly solve the associated scattering problem, obtaining new integrable solutions. Finally, we construct
lattice spin chains with defects where similar physics is expected to arise.
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All authors Andrea Antinucci, Christian Copetti, Giovanni Galati, Giovanni Rizi
Strongly Correlated Electrons · Cross-listed from hep-th
Non-Invertible Symmetries and Boundaries for Two-Dimensional Fermions
Guillermo Arias-Tamargo, Philip Boyle Smith, Rishi Mouland et al. (+1 more)
We study the relation between boundary conditions and categorical
symmetries of two-dimensional fermionic conformal field theories. We determine all anomaly-free invertible global
symmetries of two free complex Weyl
fermions, which take the form $\mathbb{Z}_k$ for each primitive Pythagorean triple $a^2 + b^2 = k^2$. The theory is self-dual under gauging any of these
symmetries, and so to each there is associated a non-invertible topological defect. We study the properties of these lines, and show that any conformal boundary condition of two Dirac
fermions that preserves a $U(1)^2$
symmetry can be found by dressing a trivial Dirichlet boundary with one of them. We discuss two microscopic descriptions of these defects:
fermions coupled to a
quantum-mechanical rotor degree of freedom; and an abelian gauge theory that realises symmetric mass generation in a half-space.
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All authors Guillermo Arias-Tamargo, Philip Boyle Smith, Rishi Mouland, Maxwell L. Velásquez Cotini Hutt
Mesoscale and Nanoscale Physics
Fermi Surface Geometry from Charge Fluctuations in Three-Dimensional Metals
Pok Man Tam, Yarden Sheffer, Xiao-Chuan Wu et al. (+2 more)
For three-dimensional non-interacting multi-band metals, we show that important information about the shape and the
quantum geometry of
Fermi surfaces is encoded in the subleading logarithmic term of bipartite charge fluctuations. This logarithmic term is related to the dimensionless $|\mathbf{q}|^3$-coefficient of the structure factor in momentum space, and both quantities can be expressed as
Fermi surface integrals of the
Fermi surface
curvature tensor and the
quantum metric tensor. When the real-space partition surface is a quadric (i.e., sphere or ellipsoid), the logarithmic coefficient satisfies a topological bound depending only on the Euler characteristic and the Chern number of the
Fermi surface, illustrating a non-trivial interplay between
topology and
quantum topology in multi-band metals.
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All authors Pok Man Tam, Yarden Sheffer, Xiao-Chuan Wu, F. D. M. Haldane, Shinsei Ryu
Strongly Correlated Electrons
Quantum Monte Carlo fermion spectroscopy of a non-compact CP$^1$ model
Xu Zhang and Nick Bultinck
We study a model describing electrons coupled to anti-
ferromagnetic spin fluctuations, and consider the situation where hedgehog defects in the order parameter field are suppressed. Without hedgehogs, the bosonic sector of the theory can be taken to realize the physics of the non-compact CP$^1$ theory with a deconfined U$(1)$ gauge field. After strongly coupling the
boson to
fermion spins, we simulate the single-particle spectral properties of a hedgehog-suppressed electron-
boson model defined on a
bilayer square
lattice with
Quantum Monte Carlo, and interpret the results in terms of an effective theory with fractionalized spinon and chargon excitations. As one of our main results we show that the electron gap on top of the half-filled
insulator with gapless
photon fluctuations closely resembles the mean-field dispersion of an electron in an anti-
ferromagnetic spin background, even though the system fully preserves both the translation and
spin rotation
symmetry. Finally, we discuss potential implications of our results for the high-temperature
superconductors.
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Materials Science
Rongzai agent: A Large Language Model-Based Autonomous Assistant for Rietveld Refinement of Neutron Diffraction Data
Qingmeng Li, Hao Wang, Dongbo Xiong et al. (+11 more)
Neutron diffraction (ND) is an indispensable technique for determining atomic positions (especially light elements) and thus serves as a critical probe for revealing microscopic structures in materials science. However, traditional Rietveld refinement of ND data relies heavily on manual operation of specialized software, which is time-consuming, labor-intensive, and highly dependent on user expertise, severely hindering automated analysis. The automation of Rietveld refinement has long been a long-standing and challenging problem in crystallography. To address this challenge, this paper presents the Dr.Sai-Rongzai
agent, an autonomous refinement assistant based on a large
language model (LLM), a specialist knowledge base, and the GSAS-II refinement engine, achieving for the first time an intelligent refinement that integrates knowledge-driven decision-making. The
agent accomplishes a fully automated workflow from natural
language task parsing to autonomous decision-making, execution of refinement strategies, and report generation. Evaluation on five representative samples shows that the Rongzai
agent achieves lower Rwp values than human specialists on three samples (2.88% vs. 4.42%, 5.06% vs. 5.40%, 7.60% vs. 9.00%), while on the other two samples its results are very close to those of the specialists. The
agent is currently deployed at the China Spallation
Neutron Source (CSNS) and is open for external user registration, providing an intelligent and user-friendly analytical tool for materials research. This work fully leverages the cutting-edge advantages of LLM, offers a new path to solve the long-standing problem of automated refinement, takes a key step toward intelligent and fully automated crystallographic analysis, and holds great potential to accelerate AI for Science discoveries in
neutron-based materials characterization.
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All authors Qingmeng Li, Hao Wang, Dongbo Xiong, Jiajun Zhong, Wenhai Ji, Hao Hu, Yiyu Zhang, Bolun Zhang, Hong Wang, Yongfeng Zhu, Rong Du, Zhengde Zhang, Fazhi Qi, Junrong Zhang
Quantum Gases
Nagaoka supermetal in the particle-doped triangular Hubbard model
Rui Cao, Xiangyue Zhang, Hui Tan et al. (+4 more)
While the interplay of correlations and
geometric frustration in doped Mott
insulators provides a fertile ground for exotic
quantum phases, the nature of the metallic state emerging upon particle doping remains poorly understood. In this work, we investigate the triangular-
lattice Hubbard model with particle doping and provide compelling evidence for an intrinsic, interaction-driven
quantum state, which we term the Nagaoka supermetal. This state is characterized by a sublinear temperature dependence in the DC resistivity, along with singular behaviors in the charge compressibility and zero-frequency spectral weight. To understand the origin of these singular properties, we derive an effective low-energy model and demonstrate that a higher-order Van Hove singularity emerges from the reconstructed dispersion. This singularity gives rise to a power-law divergence in the density of states, capturing the anomalous properties observed in the supermetallic regime. Our findings offer a new perspective on non-
Fermi liquid states in geometrically frustrated systems and are directly accessible in current ultracold atom experiments.
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All authors Rui Cao, Xiangyue Zhang, Hui Tan, Jian-Shu Xu, Yuan-Yao He, Jianmin Yuan, Yongqiang Li
Materials Science · Cross-listed from cs.LG
Reducing cross-sample prediction churn in scientific machine learning
Gordan Prastalo and Kevin Maik Jablonka
Scientific machine learning reports predictive performance. It does not report whether the same prediction would survive a different draw of training data. Across $9$ chemistry
benchmarks, two classifiers trained on independent bootstraps of the same training set agree on aggregate accuracy to within $1.3\text{--}4.2$ percentage points but disagree on the class label of $8.0\text{--}21.8\%$ of test molecules. We call this gap cross-sample prediction churn. The standard parameter-side techniques (deep ensembles, MC dropout,
stochastic weight averaging) do not reduce this gap; two data-side methods do. The first is $K$-bootstrap bagging, which cuts the rate $40\text{--}54\%$ on every
dataset at no accuracy cost ($K{\times}$-ERM compute). The second is twin-bootstrap, our proposal: two networks trained jointly on independent bootstraps with a sym-KL consistency loss between their predictions, which at matched $2{\times}$-ERM compute reduces churn a further median $45\%$ beyond bagging-$K{=}2$. Cross-sample prediction churn deserves a column alongside predictive performance in scientific-ML
benchmark reports, because without it the parameter-side and data-side methods are indistinguishable on the metric they actually differ on.
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Strongly Correlated Electrons
Parallel Scan Recurrent Neural Quantum States for Scalable Variational Monte Carlo
Ejaaz Merali, Mohamed Hibat-Allah, Mohammad Kohandel et al. (+2 more)
Neural-network
quantum states have emerged as a powerful variational framework for
quantum many-body systems, with recent progress often driven by massively parallel architectures such as
transformers. Recurrent neural network
quantum states, however, are frequently regarded as intrinsically sequential and therefore less scalable. Here we revisit this view by showing that modern recurrent architectures can support fast, accurate, and computationally accessible neural
quantum state simulations. Using autoregressive recurrent wave functions together with recent advances in parallelizable recurrence, we develop variational ansätze, called parallel scan recurrent neural
quantum states (PSR-NQS), which can be trained efficiently within variational Monte Carlo in one and two spatial dimensions. We demonstrate accurate
benchmark results and show that, with iterative retraining, our approach reaches two-dimensional
spin lattices as large as $52\times52$ while remaining in agreement with available
quantum Monte Carlo data. Our results establish recurrent architectures as a practical and promising route toward scalable neural
quantum state simulations with modest computational resources.
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All authors Ejaaz Merali, Mohamed Hibat-Allah, Mohammad Kohandel, Richard T. Scalettar, Ehsan Khatami
Materials Science
Chiral molecule-induced contributions to ferromagnetic resonance
Jurgen Lindner, Pedro Contreras-Gallardo, Abhishek Singh et al. (+7 more)
Despite extensive research on chirality-driven
spin selectivity, most studies have focused on static
magnetic properties, while the influence of chirality on the dynamic
magnetic response remains largely unexplored. Here, we investigate how
chiral molecular interfaces affect magnetization dynamics in thin Co/Ni multilayers with perpendicular
magnetic anisotropy using broadband
ferromagnetic resonance spectroscopy. A comparison between bare (reference) films and molecule-functionalized (hybrid) samples reveals no measurable changes in either the resonance field or the linewidth that could be attributed to the presence of the
chiral environment. Motivated by our findings we develop a macrospin description that distinguishes
equilibrium modifications of the
magnetic free-energy landscape (MIPAC-type effects) from non-
equilibrium, CISS-induced
spin torques. Our analysis shows that
equilibrium modifications primarily shift the resonance condition via changes to the free energy landscape and thereby the effective field, whereas damping-like non-
equilibrium torques provide a distinct channel for varying the effective damping rate. This approach establishes clear criteria for disentangling
chiral-interface-induced energy modifications from torque-driven dynamical effects in
ferromagnetic resonance experiments.
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All authors Jurgen Lindner, Pedro Contreras-Gallardo, Abhishek Singh, Ruslan Salikhov, Anna Semisalova, Olav Hellwig, Rodolfo Gallardo, Anna Lewandowska-Andralojc, Kilian Lenz, Aleksandra Lindner
Mesoscale and Nanoscale Physics
Magnetization-dependent and stacking-tunable Edelstein effect in two-dimensional magnet 2H-VTe2
Weiyi Pan and Jaroslav Fabian
The Edelstein effect in
magnetic systems enables magnetization switching via the coupling between current-induced
spin accumulation and intrinsic
magnetic order, and is therefore highly promising for next-generation spintronic devices. Realizing and manipulating the Edelstein effect in two-dimensional (2D)
magnetic systems is particularly desirable for achieving high-efficiency and multifunctional spintronic applications. In this work, based on first-principles calculations and
symmetry analysis, we demonstrate that the Edelstein effect can intrinsically arise in the 2D in-plane
ferromagnetic semiconductor 2H-VTe2, with its behavior strongly dependent on the magnetization orientation. For monolayer 2H-VTe2 with D3h
crystal symmetry, under an applied current along the +x direction, only the time-reversal-even z component and the time-reversal-odd y(x) component of the
spin accumulation are allowed when the magnetization is aligned along +x (+y). For
ferromagnetic bilayer 2H-VTe2 in AB or BA stacking, where the
crystal symmetry is reduced to C3v, additional
spin components emerge with the presence of in-plane magnetization. Specifically, for magnetization along +x (+y), besides dSz_even and dSy_odd (dSz_even and dSx_odd), extra components such as dSy_even and dSz_odd (dSy_even) become allowed. Notably, these additional components can be reversibly switched by changing the stacking configuration from AB to BA via interlayer sliding. Our results not only deepen the understanding of current-induced
spin accumulation in 2D
magnetic systems from both
symmetry and first-principles perspectives, but also identify 2H-MX2 materials as a promising platform for realizing intrinsic and tunable Edelstein effects in high-efficiency
spin-orbit torque devices.
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Mesoscale and Nanoscale Physics
A. M. Zimmerman, Saeed Fallahi, Sergei Gronin et al. (+13 more)
Hybrid
superconductor-
semiconductor nanostructures are a central component for research spanning condensed matter physics and
quantum information processing. Continued progress relies critically on the ability to characterize, control, and optimize several intrinsic material properties including
spin-orbit coupling, band offsets, and disorder in a device-relevant stack that necessarily couples the electronic states of a superconducting metal film and a
semiconductor. Here we report a new method to extract fundamental material parameters utilizing simple Shubnikov-de Haas (SdH) oscillation measurements in
heterostructures in which metallic electronic states are coupled to a two-dimensional electron gas (2DEG) residing in an InAs
quantum well beneath an aluminum thin film. Proper analysis of the full magnetoresistance data facilitates extraction of the
quantum well carrier density,
spin-orbit coupling strength, and both transport and
quantum scattering times. Most importantly, the extracted scattering times in the 2DEG are impacted by the metal-
semiconductor coupling strength allowing us to quickly gain information on proximity-induced superconducting gap without any fabrication or mK measurements. The wealth of information that is accessed with these simple measurements positions this methodology as an important tool for hybrid materials optimization.
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All authors A. M. Zimmerman, Saeed Fallahi, Sergei Gronin, Tyler Lindemann, Patrick Sohr, Ray Kallaher, Alejandro Alcaraz Ramirez, Georg W. Winkler, Samuel M. L. Teicher, William Cole, Sebastian Heedt, Eoin O'Farrell, Gijs de Lange, Roman Lutchyn, Michael J. Manfra, John Watson
Disordered Systems and Neural Networks
Do Hopfield Networks Dream of Stored Patterns? A Statistical-Mechanical Theory of Dreaming in Multidirectional Associative Memories
Adriano Barra, Fabrizio Durante, Andrea Ladiana et al. (+1 more)
We introduce the Dreaming $L$-directional Associative
Memory (DLAM), a multi-layer Hebbian architecture in which off-line dreaming and supervised heteroassociative coupling coexist within a single energy function, placing our approach within the framework of energy-based models (EBMs). The replica-symmetric free energy, derived via the Guerra interpolation scheme, yields self-consistency equations governing the order parameters across the control-parameter space. The effective local field decomposes into signal, intra-layer dreaming noise, and inter-layer noise. Dreaming improves
retrieval by differentially attenuating high-
eigenvalue interference modes of the empirical correlation
matrix, suppressing inter-pattern crosstalk while preserving the signal. Dreaming and inter-layer coupling prove synergistic, opening
retrieval regions unreachable by either mechanism alone, as confirmed by Monte Carlo simulations for $L=3$. Their interplay is most pronounced on pattern disentanglement: given a mixture state as input, the network splits the constituent patterns one-per-layer, recovering each modality-specific pattern from a common cue that simultaneously blends noisy evidence from all sensory channels. Phase diagrams are planar projections of the hyperspace $(\alpha,\beta,\rho,t)$-where $\alpha$ is the storage load, $\beta$ the fast-noise inverse temperature, $\rho$ the
dataset entropy, and $t$ the sleeping time. In the $(\rho,t)$-plane, the diagrams reveal a data-computation trade-off: off-line consolidation substitutes for additional training data, extending to heteroassociative architectures a phenomenon previously established for autoassociative networks. Enriching the standard Hopfield model with heteroassociativity and dreaming gives rise to EBMs capable of complex tasks beyond classical pattern recognition, contributing to a modern theory of neural information processing.
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All authors Adriano Barra, Fabrizio Durante, Andrea Ladiana, Michela Marra Solazzo
Mesoscale and Nanoscale Physics
Enhanced Near-Field Thermal Radiation Driven by Multiple Corner and Edge Modes in Subwavelength Square Nanowires
Jose Ordonez-Miranda, Minggang Luo, Michele Diego et al. (+4 more)
We demonstrate that the near-field thermal radiation between subwavelength SiC nanowires with square cross sections is dominated by multiple corner and edge resonances rather than the single surface-
phonon-polariton channel of planar surfaces. Fluctuational electrodynamics simulations reveal that these resonances lie within the SiC Reststrahlen band,
redshift for thinner nanowires, and yield a four-fold enhancement of thermal conductance. This maximum enhancement occurs when the separation gap nearly matches the nanowire thickness, balancing dimensional confinement and interwire coupling. These findings establish square nanowires as a versatile platform for geometrycontrolled near-field heat transfer in nanoscale heat management and energy conversion.
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All authors Jose Ordonez-Miranda, Minggang Luo, Michele Diego, Roman Anufriev, Victor Guillemot, Masahiro Nomura, Sebastian Volz
Materials Science
Giant optical spin-orbit interactions in ferroelectric van der Waals waveguides
Ding Xu, Saeed Rahmanian Koshkaki, Vicente Galicia et al. (+14 more)
Optical
spin-orbit interactions (SOI) link photonic
spin to momentum, offering a route toward on-chip polarization control and beam steering. Nevertheless, achieving sufficient optical SOI and nonlinearities on sub-micrometer scales - a prerequisite for dense photonic integration - remains an outstanding challenge. Here, we show that highly birefringent van der Waals (vdW) waveguides provide an ideal, chip-compatible platform to address this limitation. We focus on the ferroelectric
semiconductor NbOI2, which exhibits record optical nonlinearities and dielectric anisotropy. Using femtosecond optical microscopy, we image light propagation and harmonic conversion beyond the total internal reflection barrier over tens of micrometers in NbOI2 slab waveguides. We report
giant optical
spin-splitting through the optical
spin Hall effect, which facilitates spatial separation of optical
spin currents on sub-micrometer scales, in quantitative agreement with a microscopic light-matter interaction model. We further leverage optical
spin-momentum locking to realize polarization-controlled waveguide steering. We generalize these observations across various vdW waveguides and empirically confirm a scaling law linking dielectric anisotropy to
geometric spin-splitting. Our results establish highly anisotropic vdW waveguides as an ideal platform for densely integrated opto-spintronic technologies.
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All authors Ding Xu, Saeed Rahmanian Koshkaki, Vicente Galicia, Chun-Ying Huang, Victoria Quirós-Cordero, Jakhangirkhodja A. Tulyagankhodjaev, André Koch Liston, Daniel G. Chica, Emma Lian, Amirhosein Amini, Yongseok Hong, Taketo Handa, P. James Schuck, Xiaoyang Zhu, Xavier Roy, Arkajit Mandal, Milan Delor
Materials Science
Nonlinear dynamic elastic moduli from equilibrium stress fluctuations
F. E. Garbuzov and Y. M. Beltukov
Fluctuation formulas for elastic and viscoelastic
moduli allow their computation from
equilibrium molecular dynamics simulations, avoiding explicit nonequilibrium deformation protocols. While such expressions are well established for the quasi-static
moduli, and also the linear dynamic
moduli, no fluctuation formula exists for the nonlinear time-dependent
moduli that govern anharmonic viscoelastic response under finite time-dependent strains. In this work we derive transient-time correlation function expressions for both the linear and the nonlinear dynamic
moduli, starting from the DOLLS/SLLOD equations of motion for irrotational motion. The resulting formulas involve
equilibrium time correlations of the stress tensor and Born-kinetic terms, and they recover the known quasi-static and linear dynamic results in the appropriate limits.
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Statistical Mechanics · Cross-listed from quant-ph
Berry-Phase-Induced Chirality in Thermodynamics
Zhaoyu Fei and Yu-Han Ma
Geometric phases are foundational to isolated
quantum systems, yet their thermodynamic role in open systems remains unrevealed Developing a dissipative adiabatic perturbation expansion, we discover a Berry-phase-induced
chiral work difference that survives decoherence. This chirality evolves from an interferometric thermodynamic Aharonov-Bohm effect in the
unitary regime to a fringe-free signal in the dissipative regime. We illustrate this framework in a two-level system and assess its experimental feasibility. Our findings clarify the role of
quantum geometry in the
geometric formulation of thermodynamics.
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Soft Condensed Matter
Theory of fracture initiation and propagation in viscoelastic media
Giuseppe Carbonea, Cosimo Mandriotab, Guido Violanob et al. (+2 more)
Crack initiation and propagation are fundamental problems in materials science, often leading to catastrophic failure. While fracture in elastic solids occurs instantaneously above a critical load, viscoelastic materials may sustain high loads for a finite time before cracks start to propagate. This phenomenon, known as delayed fracture, has been widely observed experimentally but is still only partially understood theoretically. In this study, we present a rigorous framework based on the Lagrange–d'Alembert principle of virtual work (PVW) to predict both the viscoelastic delay time and the subsequent crack
evolution under arbitrary loading histories. We derive how the delay time depends on the applied remote load and validate the theory through quantitative comparison with experiments, using directly measured delay times together with DMA-based viscoelastic characterization of the material. Very good agreement is obtained over a broad range of loading and delay times. Our results also show that crack propagation starts at finite speed and that load-dependent steady-state conditions are soon established. Finite element analyses further support the proposed framework and clarify the role of finite-ranged adhesion forces at fixed adhesion energy, showing that shorter interaction ranges yield results in quantitative agreement with theory. We also present, for the first time, a rigorous J-integral formulation valid for linear viscoelastic solids under arbitrary, time-varying loading histories. The result restores path independence and yields a generalized Griffith criterion that naturally predicts delayed fracture initiation in non-conservative materials. Remarkably, fracture initiation can be described without specifying the detailed stress distribution within the process zone, as long as it remains small relative to the crack length.
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All authors Giuseppe Carbonea, Cosimo Mandriotab, Guido Violanob, Luciano Afferrante, Nicola Menga
Materials Science
High-Pressure XRD Study of Ti-3Al-2.5V Titanium Alloy: Intermediate Transition Pressure and Composition Trends in Ti-Al-V Alloys
D. Errandonea, R. Turnbull, P. Botella et al. (+3 more)
High-pressure X-ray diffraction experiments were performed on Ti-Al-V
alloys to investigate the effect of composition on structural stability, focusing on Ti-3Al-2.5V and comparing with pure Titanium and Ti-6Al-4V. Measurements using different pressure-transmitting media show a phase transition in Ti-3Al-2.5V at 17-19 GPa, intermediate between pure Ti (5-10 GPa) and Ti-6Al-4V (~30 GPa). Despite variations arising from the choice of pressure medium, the transition pressure shows a clear and systematic increase with higher Al and V content. Equation-of-state analysis indicates that the bulk modulus remains nearly unchanged across compositions. This suggests a decoupling between elastic properties and phase stability, with alloying primarily affecting the transition pressure rather than compressibility. These results highlight the role of composition in tuning high-pressure phase transformations in Ti-Al-V based
alloys.
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All authors D. Errandonea, R. Turnbull, P. Botella, R. Oliva, C. Popescu, S. MacLeod
Superconductivity
Nodal Topological Superconductivity Driven by Crystalline Antiunitary Symmetry in Altermagnets
Xiao Xiao and Arun Bansil
Topological superconductivity hosts protected quasiparticles and is central to topological
quantum computation, yet its realization in intrinsic materials remains challenging and often relies on engineered platforms. Here we uncover a
symmetry-constrained mechanism for nodal topological superconductivity in altermagnets. Focusing on fourfold rotational collinear altermagnets, we show that the native crystalline antiunitary
symmetry $\mathcal{T}C_{4z}$ generically forbids pure
spin-singlet pairing and selects pairing structures that admit Bogoliubov-de Gennes (BdG)
Hamiltonians with emergent
chiral symmetries. These
symmetries further give rise to robust nodal topological phases over broad parameter regimes, including a nodal-point phase hosting Majorana flat bands (MFBs) and two distinct nodal-loop phases with
chiral Majorana edge states. Notably, the nodal structure persists even after spontaneous breaking of the antiunitary
symmetry, indicating that the
topology originates from
symmetry-constrained pairing rather than direct
symmetry protection. Finally, we propose tunneling signatures that can distinguish these nodal phases and probe
symmetry breaking experimentally.
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Materials Science
Layer thickness dependent band gap of MBE grown single- to few-layer MoS$_{2}$
Maciej Bazarnik, Thorsten Deilmann, Marta Przychodnia et al. (+1 more)
In light of the rise of transition metal dichalcogenides as 2D
semiconductors for device applications, band engineering becomes very important from an application point of view. In many of these materials, such as the canonical example of MoS$_{2}$, the
semiconductor band gap depends on the layer number. It changes from indirect to direct as it evolves from a bulk
semiconductor to a monolayer. Interestingly, it was predicted and experimentally confirmed that, by thinning the material from bulk to a
bilayer, the indirect transition shows a strong blue-shift. Here, we present the results of scanning tunnelling spectroscopy measurements on MoS$_{2}$ that has been grown in situ via molecular beam epitaxy on
graphene on Ir(111) at thicknesses ranging from 1 to 5 layers. We find a drastic decrease of the band gap with increasing layer number, to values even below the band gap in bulk. We also observe that the pinning of the conduction band vanishes above 4 layers. Comparing our experimental data with density functional theory and GW calculations indicates that an additional screening is introduced by the sample growth conditions.
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All authors Maciej Bazarnik, Thorsten Deilmann, Marta Przychodnia, Anika Schlenhoff
Statistical Mechanics
Thermodynamic Geometry of two-dimensional square-well fluids
Jaime Jaramillo-Gutiérrez and José Torres-Arenas
Thermodynamic geometry of two-dimensional fluids has been investigated using a square-well model as a prototype fluid. A comparison with the three-dimensional case is performed in the subcritical and supercritical domains of thermodynamic space. In the subcritical region, it is found that the R-crossing method has a narrower range of validity for two-dimensional fluids compared to three-dimensional ones. On the other hand, in the supercritical region, an analysis of different Widom lines, including the R Widom line, shows that for two-dimensional fluids these lines extend further into the supercritical region than their three-dimensional counterparts. A similar behavior is observed for the validity of the Clausius–Clapeyron equation in two-dimensional fluids.
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Materials Science
OpenAaaS: An Open Agent-as-a-Service Framework for Distributed Materials-Informatics Research
Peng Kang, Bixuan Li, Xiaoya Huang et al. (+5 more)
The Materials Genome Initiative catalyzed the proliferation of centralized platforms–SaaS, PaaS, and IaaS–that aggregate computational and experimental resources for accelerated materials discovery. In parallel, breakthroughs in large
language models (LLMs) and autonomous
agents have created powerful new
reasoning capabilities for scientific research. Yet a critical "last mile" problem remains: while we possess world-class models and vast repositories of materials data, we lack the organizational infrastructure to compose these capabilities securely across institutional boundaries. The development of structural and functional materials for harsh service environments–high-temperature
alloys, radiation resistant steels, corrosion-resistant coatings–remains characterized by long-term iteration, mechanistic complexity, and high domain expertise–demands that exceed both monolithic
agent systems and traditional centralized platforms. To address this gap we propose OpenAaaS, an open-source hierarchical and distributed
Agent-as-a-Service framework that enables organized multi-
agent collaboration for intelligent materials design. OpenAaaS is built on a single foundational principle: code flows, data stays still. A Master
Agent plans and decomposes complex research tasks without requiring direct access to subordinate
agents' managed data and computational resources. Sub-
agents, deployed as near-data execution nodes, retain full sovereignty over local
datasets, proprietary
algorithms, and specialized hardware. This architecture guarantees that raw data never leaves its domain of origin while enabling cross-scale, cross-domain secure integration of previously isolated materials intelligence silos. We validate the framework through two representative case studies: (i) AlphaAgent, an evidence-grounded materials literature analysis executor that achieves 4.66/5.0 on deep analytical questions against single-pass RAG baselines; and (ii) an ultra-large-scale hexa-high-
entropy alloy descriptor database service that demonstrates secure near-data execution and domain-specific scientific workflows under strict data-sovereignty constraints. OpenAaaS establishes a principled pathway toward "organized research" via
agent collectives, offering a scalable foundation for next-generation materials intelligent design platforms. All source code is available at https://github.com/Wolido/OpenAaaS.
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All authors Peng Kang, Bixuan Li, Xiaoya Huang, Shuo Shi, Weiqiao Zhou, Zhen Li, Yu Liu, Lei Zheng
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Deep Learning as Neural Low-Degree Filtering: A Spectral Theory of Hierarchical Feature Learning
Yatin Dandi, Matteo Vilucchio, Luca Arnaboldi et al. (+2 more)
Understanding how deep neural networks learn useful internal representations from data remains a central open problem in the theory of deep learning. We introduce Neural Low-Degree Filtering (Neural LoFi), a stylized limit of gradient-based training in which hierarchical feature learning becomes an explicit iterative spectral procedure. In this limit, the dynamics at each layer decouple: given the current representation, the next layer selects directions with maximal accessible low-degree correlation to the label. This yields a tractable surrogate mechanism for deep learning, together with a natural kernel-space interpretation. Neural LoFi provides a mathematically explicit framework for studying multi-layer feature learning beyond the lazy regime. It predicts how representations are selected layer by layer, explains how emergence of concepts arises with given sample complexity, and gives a concrete mechanism by which depth progressively constructs new features from old ones through low-degree compositionality. We complement the theory with mechanistic experiments on fully connected and convolutional architectures, showing that Neural LoFi improves over lazy random-feature baselines, recovers meaningful structured filters, and predicts representations aligned with early gradient-descent feature discovery with real
datasets.
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All authors Yatin Dandi, Matteo Vilucchio, Luca Arnaboldi, Hugo Tabanelli, Florent Krzakala
Materials Science
Magnetocaloric Effect in Nanostructured $La_{0.6}Sr_{0.4}Fe_{1-x}Co_{x}O_3$
Fabiana N. Morales Alvarez, Mariano Quintero and Joaquín Sacanell
This work presents a systematic study of the magnetocaloric effect in the nanostructured perovskite series $La_{0.6}Sr_{0.4}Fe_{1-x}Co_{x}O_3$ (x = 0, 0.2, 0.5, 0.8, and 1.0), synthesized by a pore-wetting method using polymeric membranes with pore diameters of 200 nm and 800 nm. All samples were calcined at 1000{\deg}C. Structural characterization was made by X-ray diffraction and confirmed the formation of a single-phase perovskite with distorted rhombohedral
symmetry, without detectable secondary phases. We observed significant influence of substitution of Fe by Co on the morphology, as the analysis by scanning electron microscopy revealed a clear
evolution from smaller to larger particles and from thin to thicker nanotubes, as the Co content increased.
Magnetic measurements showed that the cationic substitution enhances
ferromagnetic coupling, increasing both the saturation magnetization (MS) and the Curie temperature (TC). The magnetocaloric properties, determined through the Maxwell relations, exhibit a maximum
entropy change of 1.13 J/(kg K) under an applied field of 3 T for the sample with x = 1. These results demonstrate that the combination of Co doping and controlled nanostructuring effectively optimizes the magnetocaloric response.
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Strongly Correlated Electrons
Lieb-Schultz-Mattis theorem from gauge constraints
Bhandaru Phani Parasar
We construct a $\mathbb{Z}_2 \times \mathbb{Z}_2$ gauge theory coupled to matter on a one-dimensional chain, aiming to study the ground-state physics in the Gauss law subspace. We show that the theory in the Gauss law subspace has a U$(1)$
symmetry whose generator commutes with
lattice translations, but anticommutes with the
lattice reflection operator. This leads to a Lieb-Schultz-Mattis (LSM)
theorem that always rules out a trivial gapped ground state in the Gauss law subspace, if the
hamiltonian is invariant under translations and reflection. Any point in the parameter space must realize either a spontaneously
symmetry broken (SSB) ground state, or a gapless ground state. Imposing the Gauss law is pivotal for the existence of the U$(1)$
symmetry, and hence of the LSM
theorem. We thus demonstrate a novel mechanism to obtain an LSM-type
theorem, wherein the
symmetry responsible for the
theorem originates from the kinematic constraints of a gauge theory. We identify a point in the parameter space at which the system is gapless. At the gapless point, the excitations admit a description in terms of free Dirac
fermions with a constraint on the total
fermion number. The asymptotic behavior of the two-point correlation function of the simplest local gauge-invariant quantity at the gapless point is found to be $ \propto \cos{(\pi r)}\,r^{-2/9}$, where $r$ is the
lattice separation between the two points. This model is also a natural platform to study phase diagram topological defects residing in families of SSB phases.
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Materials Science · Cross-listed from physics.geo-ph
Assessing foundational atomistic models for iron alloys under Earth's core conditions
Tianqi Wan, Liangrui Wei, Zepeng Wu et al. (+2 more)
We assess the capability of recently developed foundational atomistic models (FAMs) to simulate iron
alloys under the extreme pressures and temperatures of Earth's core. Static equations of state for hexagonal close-packed (hcp) and body-centered cubic (bcc) iron, computed using 17 FAMs, are benchmarked against ab initio calculations. Two representative models, MatterSim and MACE, are further evaluated for their ability to reproduce
phonon spectra,
liquid structure, and melting relations of iron at core conditions. While both models capture several key properties, MACE substantially overestimates the stability of bcc iron and fails to correctly describe the stability of hcp iron. Their performance is also examined for binary
liquids, superionic phases, and a seven-component Fe-Ni-Si-S-O-H-C
liquid. Although these FAMs were not explicitly trained on data from core conditions, they can reproduce several structural and dynamical properties across a wide range of compositions. However, none of the tested models consistently reproduces all first-principles
benchmarks. By analyzing the origins of these discrepancies, we identify several limitations of current FAMs, particularly the lack of an explicit treatment of thermal electronic excitations, which significantly affect phase stability and thermodynamic properties under core conditions. We further discuss directions for improving FAMs to enable predictive simulations of core-forming materials under extreme conditions.
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All authors Tianqi Wan, Liangrui Wei, Zepeng Wu, Renata M. Wentzcovitch, Yang Sun
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Ghost State of Light
R. M. de Boer, C. Toebes, Jan Klars et al. (+1 more)
We report the observation of a long-lived non-stationary state of light in a single-mode optical cavity. The observed state is a ghost of a saddle-node bifurcation which creates a bottleneck in phase space. While such ghosts are known to exist, accessing them is challenging because it requires a mechanism that steers the relaxation pathway away from the true attractor and into the bottleneck where the ghost emerges. Here we identify such a mechanism, namely a nonlinear response with
memory. Our experimental system leverages this mechanism, enabling us to observe ghost states with lifetimes exceeding the cavity
photon lifetime by more than ten orders of magnitude, even in the presence of strong fluctuations. The ghost manifests as a plateau in the relaxation dynamics of the cavity transmission, reminiscent of prethermalization. We show how the ghost lifetime depends on the
memory time and the distance to the bifurcation, and we observe signatures of scaling in the distribution of ghost lifetimes at fixed driving conditions. Our work establishes minimal conditions for realizing parametrically long-lived non-stationary states.
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All authors R. M. de Boer, C. Toebes, Jan Klars, S. R. K. Rodriguez