Materials Science
Quasiparticle phono-conversion: filming carriers coalescing into excitons
Enrico Perfetto, Takumi Fukuda, Xing Zhu et al. (+12 more)
Condensed matter physics is replete with phenomena involving high-energy free particles coalescing into low-energy bound few-particle states. While the cooling of the individual particles is well understood, the crucial step by which cold free carriers form a bound state remains elusive, involving complex energy and momentum relaxation pathways. Here, by combining ultrafast time- and momentum-resolved photoemission spectroscopy on a monolayer WSe$_2$ with the first-principles excitonic-Bloch equations, we resolve the conversion of initially free electrons and holes at the bandedges into bound
excitons. With unprecedented energy resolution, we observe the transient coexistence of free-carrier and excitonic bands, accompanied by a transfer of spectral weight between the two. We establish the phononic origin of
exciton formation and ascribe this coexistence to a sequential relaxation cascade toward the lowest-energy excitonic states, wherein intermediate states remain weakly populated. The efficiency of this process is controlled by valley multiplicity, large-momentum
phonon emission and
spin-flip processes. By elucidating how bound states emerge from their elementary constituents, our results point to strategies for engineering
exciton formation, with direct implications for optical materials and devices that operate with
excitons or free carriers.
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All authors Enrico Perfetto, Takumi Fukuda, Xing Zhu, Jacques Hawecker, Harley Suchiang, Joanna Nadolna, Nanami Tomoda, Suji Park, Houk Jang, Kenji Watanabe, Takashi Taniguchi, Michael K. L. Man, Julien Madéo, Keshav M. Dani, Gianluca Stefanucci
Superconductivity
B. J. Ramshaw
The confirmation of a bulk, topological
superconductor is a central goal of modern
quantum materials research. Despite decades of searching, no confirmed examples yet exist. A primary difficulty is that most experimental signatures of topological superconductivity are ambiguous and indirect. I review efforts to narrow the search for a
chiral topological
superconductor using measurements of elastic
moduli. In principle, these experiments can provide unambiguous thermodynamic evidence for multi-component superconductivity—a pre-requisite for
chiral superconductivity in 2D and quasi-2D materials. Despite the potential strength of this program, the results are still negative. I provide a pedagogical introduction to multi-component order parameters,
chiral topological superconductivity, and how superconducting order parameters couple to strain. I discuss ongoing efforts in heavy
fermion, iron pnictide, and Kagome
superconductors, and suggest routes for speeding up the search process, as well as other experimental tools that should be developed for the pursuit of this goal.
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Quantum Gases · Cross-listed from quant-ph
Noise-aware emulation and cross-device validation of neutral atom analog quantum processing units
Constantin Dalyac, Sergi Julià-Farré, Lucas Leclerc et al. (+26 more)
Analog
quantum processors based on Rydberg atom arrays are a powerful platform for many-body
quantum simulation, combinatorial optimization, and graph machine learning. As these devices become increasingly accessible, establishing confidence in their outputs requires predictive models that quantitatively connect microscopic hardware imperfections to empirical results. Here, we present a noise-aware emulation framework that propagates the dominant noise mechanisms throughout the full computation cycle to predict device behavior. We validate the framework by benchmarking two representative protocols,
quantum annealing and post-quench dynamics, on three Pasqal
quantum processors where classical simulations still provide ground truth. Across all three devices, the measured observables fall within the uncertainty envelopes predicted by the emulator. Beyond reproducing the data, the framework isolates which physical mechanism dominates in each operating regime, provides quantitative guidance for
algorithm design and hardware improvements, and establishes a foundation for verifying analog processors in regimes beyond classical reach.
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All authors Constantin Dalyac, Sergi Julià-Farré, Lucas Leclerc, Vittorio Vitale, Boris Albrecht, Lucas Béguin, Kemal Bidzhiev, Petru Borta, Clémence Briosne-Frejaville, Daniel J. Campbell, Dorian Claveau, Makrem Chatti, Antoine Cornillot, Julius de Hond, Anita Devi, Thomas Eritzpokhoff, Gaétan Hercé, Fergus Hayes, Soufiane Kaghad, Arun Kumar Abhimanyu, Lucas Lassablière, Mauro Mendizabal, Anton Quelle, Julien Ripoll, Henrique Silvério, Joseph Vovrosh, Guillaume Villaret, Adrien Signoles, Alexandre Dauphin
Soft Condensed Matter
Thermodynamics and Kinetics of a Three-Arm Star Polymer Translocating through a Nanopore
Bhavesh R. Sarode and Harshwardhan H. Katkar
In this work, voltage-driven translocation of uniformly charged long linear and three-arm
star polymers through narrow nanopores is investigated. Langevin dynamics simulation is performed using a coarse-grained model of the
polymer and a semi-implicit representation of the nanopore. The mean translocation time of a linear
polymer is found to be inversely proportional to the applied voltage over a wide range of voltages. In contrast, the mean translocation time of a three-arm
star polymer of the same molecular weight exhibits a pronounced deviation from this scaling relation below a threshold voltage. The threshold voltage is found to be nearly independent of the molecular weight of the
polymer, but depends on the size of the nanopore and salt concentration. Metadynamics simulation is used to estimate the free-energy landscape for the translocation of the three-arm
star polymer. Below the threshold voltage, the free energy exhibits a pronounced second barrier resulting from an entropic contribution and electrostatic interactions between segments of the trailing arm inside the nanopore. A Fokker-Planck model developed using the estimated free-energy accurately predicts the deviation from the scaling relation below the threshold voltage and shows a remarkable agreement with the Langevin dynamics simulation results using a voltage-independent fitting parameter. The agreement between the theory and the Langevin dynamics simulation results is seen for different nanopore radii, molecular weights of the
polymer and salt concentrations studied. A simple extension of the free energy landscape is suggested to predict translocation kinetics for higher molecular weights of the
polymer without performing additional computationally expensive simulations.
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Quantum Gases
FFLO transition and quantum criticality in polarized Fermi gases
Francesco Pirolo, Leonardo Pisani and Pierbiagio Pieri
We investigate the zero-temperature transition from the polarized normal phase to the FFLO state in a two-dimensional
Fermi gas by means of a diagrammatic t-
matrix approach. We first show that the standard non-self-consistent theory produces an unphysical phase diagram because of a severe violation of the Luttinger
theorem. Motivated by this observation, we introduce a minimal self- consistent extension that largely restores compliance with the Luttinger
theorem while preserving the analytical simplicity of the original formalism. This leads to a physically consistent phase diagram over the whole interaction range. Building on this improved description, we characterize the
quantum critical behavior of the FFLO transition through the quasiparticle decay rates, quasiparticle weights, momentum distributions, and the critical dynamics of both fermionic and bosonic degrees of freedom. We further compare the two- and three-dimensional systems, showing that their critical properties can be understood within a unified geometrical picture based on the nesting of the majority and minority
Fermi surfaces. Finally, for the three-dimensional case, we demonstrate within the Hertz-Millis framework that vertex corrections are irrelevant, thereby placing the FFLO
quantum phase transition in the mean-field universality class, in close analogy with itinerant antiferromagnets.
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Strongly Correlated Electrons
Coupled Spin-Density-Wave and Bond-Order Driven Metal-Insulator Transition in Altermagnetic CsCr$_2$S$_2$O
Chenchao Xu, Wansheng Bai, Guo-Xiang Zhi et al. (+4 more)
A metal-
insulator transition (MIT) driven by bond order (BO) coupled with a secondary
spin-density wave (SDW) is identified in CsCr$_2$S$_2$O. Such coupling is enabled as a result of the broken time-reversal
symmetry due to the pre-existing C-type
antiferromagnetic (C-AFM) order. First-principles calculations reveal an orbital-selective physics that Cr-$d_{yz}$ orbitals form local moments and establish the altermagnetic order, while the Cr-$d_{xz}$ orbitals remain metallic and hybridize with S-$p_z$. Thus the low-energy physics is governed by the Cr-$d_{xz}$ and S-$p_z$ orbitals. On-site interactions then enhance a secondary SDW ($s$SDW) instability of the itinerant $d_{xz}$ electrons, which couples to the Cr-$d_{xz}$-S-$p_z$ bonding order. The resulting coupled $s$SDW-BO simultaneously produces experimentally observed structural distortion, charge disproportionation, local Cr-moment modulation, and gap opening. Our results establish an orbital-selective mechanism upon which pre-existing altermagnetism and electronic correlations cooperate to drive a structural MIT.
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All authors Chenchao Xu, Wansheng Bai, Guo-Xiang Zhi, Yi Liu, Xiaoqun Wang, Jianhui Dai, Chao Cao
Soft Condensed Matter
Influence of Rotational Diffusion on Macromolecular Self-Assembly Kinetics
Prabeen Kumar Pattnayak, Aloke Kumar and Gaurav Tomar
Macromolecular self-assembly underlies a plethora of biological processes and provides a versatile route for fabricating functional soft materials. The kinetics of self-assembly in solution are inherently
stochastic and are fundamentally governed by the interplay of translational and rotational
diffusion of the constituent macromolecules. While most computational studies model macromolecules as patchy spherical colloids, thereby neglecting the influence of
polymer architecture and internal conformational dynamics, the role of these factors in macromolecular self-assembly kinetics remains poorly understood. Here, we investigate the self-assembly of two patchy macromolecules with different architectures, namely linear chains and
star polymers with four and seven arms. The hydrodynamic radii of the macromolecules are chosen to be nearly identical, thereby matching their translational
diffusion coefficients and thus isolating the influence of rotational
diffusion on the self-assembly process. The binding probability of the patchy macromolecules is found to depend strongly on their internal architecture. Furthermore, reactive path density analysis reveals that self-assembly pathways are influenced by the rotational
diffusion coefficient of the individual macromolecules. Overall, this study establishes a bridge between the
equilibrium dynamics of macromolecules and their self-assembly kinetics, highlighting the importance of
polymer internal architecture in the process of self-assembly.
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Mesoscale and Nanoscale Physics
Current-based RF charge sensing in a carbon nanotube
Marta Cagetti, Stefan Forstner, Victor Champain et al. (+8 more)
Ultra-sensitive charge detection is a widely used tool for
quantum electronics with applications in
quantum information processing and in probing the physics of condensed matter systems. Existing approaches require either an impedance-matched resonant
circuit, or millimeter-scale proximity between amplifier and sample, both adding complexity and constraining device design. In this work, we introduce a current-mode charge sensor in a suspended carbon nanotube, operating at the $1.25$ MHz resonance of an RLC tank
circuit and achieving a charge sensitivity of $0.15~\mu e/\sqrt{\mathrm{Hz}}$. We utilize it to measure a double
quantum dot (DQD) electrostatically defined in the same nanotube, revealing a highly regular charge stability diagram. We perform single-shot readout of the DQD charge state at an integration time of $3.56~\mu\mathrm{s}$, without any false assignments over $10^{7}$ measurements and a signal-to-noise ratio of 17 exceeding the state of the art.
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All authors Marta Cagetti, Stefan Forstner, Victor Champain, Roger Tormo-Queralt, Christoffer B. Møller, Sergio L. De Bonis, Chandan Samanta, Elsa Vázquez-Rodriguez, Eneko Mateos-Madinabeitia, David A. Czaplewski, Adrian Bachtold
Materials Science
Charge-to-spin conversion in epitaxial and polycrystalline Bi and Bi/Ag layers
Federica Nasr, Emir Karadža, Santos F. Alvarado et al. (+9 more)
Bi is predicted to be an efficient generator of
spin-orbit torques (SOTs), with charge-to-
spin conversion efficiency comparable to those of prototypical heavy metals, such as Ta, W, and Pt. However, experimental reports provide widely scattered interconversion efficiencies, while the origin of the large conversion signal in Bi/Ag
bilayers remains controversial. Here, we investigate charge-to-
spin conversion in epitaxial and polycrystalline Bi-based
magnetic heterostructures by measuring the damping-like SOT using magneto-optic Kerr effect magnetometry, complemented by structural and spectroscopic analyses and harmonic
Hall resistance measurements. We show that inserting an Ag spacer between Bi(001) and metallic ferromagnets (FeCo or Ni) enhances the SOT efficiency by more than one order of magnitude, reaching an effective
spin Hall conductivity of approximately $2 \times 10^5 (\hbar/2e)$ S/m, in excellent agreement with theoretical expectations for bulk Bi. This enhancement can be consistently explained by the preservation of the structural and chemical integrity of Bi, otherwise compromised by the direct deposition of a
ferromagnetic overlayer, rather than by Rashba
spin-orbit coupling at the Bi/Ag interface. Comparative studies across epitaxial, polycrystalline, and intentionally surface-oxidized Bi films, beyond oxygen doses known to destroy Bi(001) surface states, reveal that structural disorder has a negative impact on the SOT efficiency and indicate a dominant bulk contribution to
spin-current generation in Bi/Ag
heterostructures, yielding an effective Bi
spin Hall angle of approximately 1. By establishing a direct correlation between atomic-scale integrity and charge-to-
spin conversion, this study provides design principles to improve the reliability of Bi-based SOT devices and offers a robust framework for interpreting
spin-charge interconversion in Bi and Bi/Ag systems.
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All authors Federica Nasr, Emir Karadža, Santos F. Alvarado, Federico Binda, Tobias Goldenberger, Carlo Zucchetti, Myriam H. Aguirre, Paolo Moras, Andrey V. Matetskiy, Polina M. Sheverdyaeva, Paul Noël, Pietro Gambardella
Mesoscale and Nanoscale Physics
Effects of gold cluster intercalation in graphene: stationary waves and modified QPI features
Cristina Bena, Marion Cranney, Poonam Kumari et al. (+2 more)
Gold intercalation beneath epitaxial
graphene on SiC produces a cluster phase with unusual standing waves and quasiparticle-interference (QPI) features concentrated near the
graphene M points. We show that this can be explained by Au intercalation below
graphene hollow sites, which induces a local scattering potential on the six surrounding carbon atoms. Within a T-
matrix treatment, this ring-like scatterer produces elliptical QPI structures centered near M, in agreement with the experimental FT-STS measurements. We further show that these QPI features naturally generate the nearly stationary standing-wave patterns observed in real space. Finally, we compute the local-density-of-states contrast on and off a small cluster and show that its sign and magnitude are strongly energy dependent, consistent with the experimental observations.
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All authors Cristina Bena, Marion Cranney, Poonam Kumari, Alberto Zobelli, Laurent Simon
Mesoscale and Nanoscale Physics
An iterative method bridging DFT, disorder averaging, and experiment in intercalated materials: application to Au-intercalated graphene
Poonam Kumari, Alberto Zobelli, Igor de Melo Froldi et al. (+3 more)
Intercalation can strongly modify the electronic dispersion of a host material, as directly revealed by angle-resolved photoemission spectroscopy (ARPES). We develop a general iterative method combining density functional theory (DFT), tight-binding (TB), disorder averaging within the self-consistent T-
matrix approximation (SCTMA), and experiment, to construct an effective model of the intercalated system. DFT identifies the relevant microscopic degrees of freedom and constrains selected model parameters, while comparison of SCTMA calculations with experiment guides their further refinement. We apply this method to
graphene intercalated with Au clusters and show that it reproduces the main ARPES signatures of the Au-cluster phase, including the broadening of the V12an Hove singularity and the emergence of kink-like features in the dispersion. The essential microscopic ingredients identified by the analysis are the hybridization between selected intercalant orbitals and the
graphene states, together with an intercalation-induced local scattering potential.
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All authors Poonam Kumari, Alberto Zobelli, Igor de Melo Froldi, Adeline Crepieux, Laurent Simon, Cristina Bena
Materials Science
Intertwined magnetoresistance and Hall multifunctionality in a non-coplanar magnetic Weyl semimetal DyB4
Long Chen, Yulin Shen, Songxue Chi et al. (+4 more)
Anomalous magneto-transport responses provide complementary probes of orbital motion, momentum-space
topology, and real-space
spin chirality, yet their integration into a single material remains rare because their underlying requirements often compete. A promising materials-design strategy is to realize a
magnetic Weyl semimetal that combines linearly dispersive high-mobility bands with tunable non-coplanar magnetism while limiting
spin-dependent scattering. Here we identify DyB4, a frustrated rare-earth tetraboride, as a
magnetic Weyl semimetal candidate that embodies this strategy and hosts intertwined magnetoresistance and
Hall multifunctionality.
Neutron diffraction reveals a sequence of field-tunable
magnetic states, including non-coplanar
spin configurations and PT-
symmetry-broken phases. First-principles calculations identify steep linear dispersions and field-induced Weyl points near the
Fermi level. Magneto-transport measurements establish a rare fourfold combination of extremely large magnetoresistance,
chiral-anomaly-like negative magnetoresistance, large anomalous
Hall conductivity arising from cooperative intrinsic Berry
curvature and skew scattering, and scalar-
spin-chirality-driven topological
Hall responses. This multifunctionality arises from the distinct yet weakly coupled roles of itinerant carriers and localized 4f moments, which enable high-mobility transport, field-induced Weyl
topology, and non-coplanar magnetism. DyB4 therefore provides a 4f-electron platform for correlating orbital transport, momentum-space Berry
curvature, and real-space
spin chirality, suggesting a route toward multifunctional
magnetic topological materials.
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All authors Long Chen, Yulin Shen, Songxue Chi, Seunghoon Song, Yang Zhang, Jian Liu, Haidong Zhou
Statistical Mechanics
Synchronization, Kinematic Waves and Spike-Phase-Separation in Feedback Ising Neural Networks on Heterogeneous Graphs
Anna Poggialini, Irem Topal, Fabrizio Lombardi et al. (+1 more)
Structural heterogeneity constrains collective dynamics in complex systems. However, its analytical tractability out of
equilibrium remains limited. In this work, we study a class of kinetic Ising neural networks driven out of
equilibrium by a homeostatic feedback loop between the neuronal excitability and the population firing rate. Using a Curie-Weiss heterogeneous mean-field approximation validated by Monte Carlo simulations, we provide an analytical characterization of how a macroscopic synchronized limit cycle emerges via an Andronov-
Hopf bifurcation on heterogeneous networks. We derive closed-form phase boundaries and show that the onset of oscillations is explicitly controlled by network heterogeneity through the degree moment ratio. Degree heterogeneity decouples the spiking rate per
neuron m from the spiking rate per synapse u, generating physical phenomena absent in homogeneous systems. These include (i) kinematic waves of sequential, degree-ordered activations propagating from the network periphery to the hubs, and (ii) a low-temperature phase-separated state emerging via a pitchfork bifurcation. We prove that for highly heterogeneous
topologies, this phase-separated fixed point stabilizes and dynamically destroys the synchronized limit cycle. These results provide a mathematical framework for understanding how heterogeneity regulates macroscopic oscillations and out-of-
equilibrium transitions in neural networks
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All authors Anna Poggialini, Irem Topal, Fabrizio Lombardi, Daniele De Martino
Materials Science
"Anomalous Solid Solution" in Ultra-High Melting Point Oxides: A New Strategy for Developing Ultra-High Temperature Thermal Protection Coatings
Yubo Wang, Hong Meng, Pengfei He et al. (+7 more)
The high-temperature performance of ultra-high temperature ceramics (UHTCs) in atmospheric environment is fundamentally governed by their melting points of oxidation products. Typical high-melting-point
oxides, such as ZrO2, undergo phase transformations at elevated temperatures, leading to structural instability. Although doping with rare-earth or transition-metal cations can suppress these transformations, it often results in a reduction in melting point, thereby limiting practical service temperature. Here, ytterbia-stabilized zirconia (YbSZ) coatings are prepared via atmospheric
plasma spraying, achieving a remarkable increase in the melting point of ZrO2 to approximately 2850 $^\circ\mathrm{C}$ and raising the ultimate
plasma and oxyacetylene ablation temperature up to nearly 2780 $^\circ\mathrm{C}$ and 3200 $^\circ\mathrm{C}$, which is the highest temperature resistance property as reported. Notably, this performance enhancement originates from a synergistic mechanism of strengthened ionic-covalent mixed bonding and improved oxygen vacancy stability. Based on these findings, the concept of "anomalous solid solution" is firstly proposed to be used in the area of ultra-high temperature protection, which provides new insights into the compositional design of UHTC systems.
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All authors Yubo Wang, Hong Meng, Pengfei He, Shujun Hu, Chuan Sun, Ximing Duan, Xiaopeng Lu, Dingwang Yuan, Wangyu Hu, Xiubing Liang
Statistical Mechanics
Interacting Quantum Symmetric Exclusion Process
Denis Bernard, Friedrich Hübner and Stefano Scopa
We introduce and solve the Interacting
Quantum Symmetric Exclusion Process (IQSEP), a family of models describing the
stochastic quantum hopping of charged particles along the edges of a
lattice, with hopping amplitudes that depend on the occupations of neighbouring sites. In the absence of interactions, they reduce to the standard
quantum simple symmetric exclusion process, exhibiting coherent diffusive transport. For interactions of order one, they capture incoherent diffusive transport and its fluctuations, characterized by density-dependent diffusivity and mobility, making contact with the macroscopic fluctuation theory. By rescaling the interaction strength appropriately with the
lattice mesh, we define a mesoscopic scaling regime that retains a finite coherence length in the continuous thermodynamic limit. This regime interpolates between coherent behavior at small length scales and incoherent behavior at large scales. The resulting scaling theory accounts for fluctuations of
quantum coherences in interacting diffusive systems, going beyond the scope of standard fluctuating hydrodynamics.
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Materials Science
Negative Thermal Expansion in Cubic Ice: A Collective Quantum Effect of the hydrogen-bond network
Loan Renaud, Tomasz Poreba, Richard Gaal et al. (+3 more)
We report
neutron powder diffraction measurements and path-integral molecular dynamics simulations of stacking-disorder-free cubic ice I$_c$, produced by topotactic degassing of C2 hydrogen hydrate. Across the cryogenic stability range, ice I$_c$ exhibits a density maximum near 70 K, closely matching that of hexagonal ice I$_h$ despite their different long-range stacking sequences. Negative thermal expansion in ice I is therefore not specific to hexagonal stacking, but arises from the shared open tetrahedral hydrogen-bond network. Simulations with the MB-pol potential quantitatively reproduce the experimental anomaly only when
nuclear quantum effects are included. The density maximum coincides, within the temperature resolution, with maximal anisotropy of the
proton quantum distribution.
Neutron-derived displacement parameters independently reveal a strongly enhanced transverse
proton displacement, while
phonon calculations identify low-frequency transverse modes with the most negative Grüneisen parameters. Together, these results establish the negative thermal expansion of ice I as a collective
quantum effect governed by
nuclear statistics and the dynamics of the hydrogen-bond network.
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All authors Loan Renaud, Tomasz Poreba, Richard Gaal, A. Marco Saitta, Michele Casula, Livia Eleonora Bove
Soft Condensed Matter
Rheology of dense suspensions of granular spherocylinders by particle-based simulation
Alex Dixon, John Hone, Gavin Melaugh et al. (+1 more)
Dense suspensions of rod-shaped granular particles are widespread in nature and manufacturing, where their fluid mechanical properties are often paramount. We have developed a particle-based simulation that models such suspensions under simple shear flow, providing predictions of the viscosity and microstructure for a given solids volume fraction and particle aspect ratio. The model tracks the trajectories of spherocylindrical rods under the action of short-range frictional contact and hydrodynamic forces, inspired by similar tools that have generated new insight into suspensions of granular spheres. It incorporates new schemes for the computation of lubrication forces between spherocylinders and the dynamic determination of the timestep. For aspect ratios up to 20, the model predicts a viscosity spike at shear start-up, giving way to steady state viscosities that increase systematically with volume fraction and aspect ratio. Likewise, particle
alignment increases with volume fraction up to an aspect-ratio-dependent critical point. Our model corroborates the limited experimental rheology data available for suspensions of granular rods, and offers a tool for fundamental exploration of the fluid mechanics, microstructure and rheology of this widespread material.
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All authors Alex Dixon, John Hone, Gavin Melaugh, Christopher Ness
Materials Science · Cross-listed from physics.app-ph
Vibe-FDTR: An agent-oriented framework for reproducible frequency-domain thermoreflectance data analysis
Fuwei Yang, Weiheng Li and Bai Song
Frequency-domain thermoreflectance (FDTR) is a
laser pump-probe technique widely used to measure thermal properties at the micro- and nanoscale; however, it relies on a complex data analysis procedure that demands substantial domain expertise and is susceptible to subtle human errors. Here, we present Vibe-FDTR, an
agent-oriented framework that enables large
language model (LLM)
agents to perform reliable and reproducible FDTR analyses directly from natural
language requests. This framework couples a configuration-driven FDTR code package, which enforces physical and parametric consistency, with procedural
agent skills that translate user intentions into organized and verifiable analysis steps. We evaluate Vibe-FDTR using a controlled
benchmark with two levels: synthetic single-step tasks and real-data multi-step tasks based on measurements of gold-coated graphite samples. Across the two levels,
agents using Vibe-FDTR achieve success rates of 100% and 98.9%, respectively. In sharp contrast, ablating skills (Code-
agent) reduces performance to 91.4% and 36.7%, which drops further to 38.6% and 0% when the domain package is also omitted (
Agent-only). Beyond success rate, Vibe-FDTR also reduces computational cost by 87.7% relative to the Code-
agent variant and cuts execution time by more than 60%. Finally, an optional expert mode supports experimental planning via autonomous sensitivity and uncertainty evaluations, and formulates physically grounded recommendations for underspecified tasks. These results demonstrate that encapsulating domain code and expert knowledge into
agent skills offers a promising route toward low-barrier, autonomous, and trustworthy thermal metrology.
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Mesoscale and Nanoscale Physics · Cross-listed from math-ph
Consistent symmetry breaking and topological phases
Yuezhao Li and Guo Chuan Thiang
Operators invariant under a
symmetry group are also invariant under any finite-index subgroup. The equivariant indices of such operators must be consistent under
symmetry breaking. We use this principle to establish a canonical weak/strong dichotomy for equivariant indices, building on an idea originating in the theory of topological
insulators in solid-state physics. We also study the relationship to coarse-
geometric, or macroscopic, indices.
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Disordered Systems and Neural Networks
Semi-supervised Hopfield model: Theoretical and Numerical results
Linda Albanese, Andrea Ladiana and Andrea Lepre
In the daily practice of Machine Learning, fully labeled
datasets are a luxury: labels demand expensive and time-consuming human annotation, whereas raw, unlabeled data can be harvested automatically and in bulk. Semi-supervised learning, where the network jointly exploits the few labeled and the many unlabeled examples at its disposal, is the standard answer to this asymmetry, yet a statistical mechanical theory of semi-supervised Hebbian learning is still lacking. In this paper we fill this gap for the Hopfield network: we prescribe a synaptic coupling given by the convex combination, weighted by a mixing parameter \lambda in [0,1], of the supervised and unsupervised Hebbian kernels built from the same archetypes, and we solve for the emergent computational capabilities of the resulting network. A signal-to-noise analysis yields the one-step Mattis magnetization and the learning threshold, i.e. the minimum
dataset size for stable
retrieval. Using Guerra's interpolation, we then derive the Replica Symmetric quenched pressure in the high-storage regime, treating the correlated disorder generated by the supervised and unsupervised channels through a particular eigen-channel decomposition. The resulting phase diagram shows that a mixed strategy outperforms both pure protocols. Finally, we prove that the quenched pressure is convex in \lambda, so thermodynamics cannot select an interior mixture: \lambda is therefore a learning hyperparameter. All the analytical findings are successfully checked against extensive Monte Carlo simulations.
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Statistical Mechanics
From Exponential to Gaussian Tails: Fractal Wavefront Scaling and the $\kappa$-Weibull Distribution at Phase Transitions
O.V. Pavlovsky and M.Yu. Satleikin
The paper examines the features of critical
evolution in an active medium modeled by a cellular automaton. The system evolves according to
stochastic rules, exhibiting two qualitatively distinct dynamical regimes: one of fading activity and another of all-filling activity waves. Each regime is characterized by its own fractal dimension and fluctuation statistics, both of which are analyzed in detail. Within the critical interval, the system displays a nontrivial fractal dimension and a fluctuation distribution that bridges the two regimes. This bridging behavior arises because, in the critical interval, the dynamics are governed by avalanches.
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Statistical Mechanics
Three-Dimensional Kardar–Parisi–Zhang Scaling in Polariton Condensates
Junhui Cao, Denis Novokreschenov, Artem Alexandrov et al. (+2 more)
Kardar–Parisi–Zhang (KPZ) universality provides an example of macroscopic scaling generated by microscopic violation of detailed balance. While one- and two-dimensional realizations have been explored in driven condensates and growing interfaces, demonstrating KPZ scaling in three spatial dimensions remains a major challenge. Here we propose a three-dimensional
exciton-polariton
crystal as a platform for observation of 3D KPZ universality. Starting from a
stochastic driven-dissipative Gross-Pitaevskii equation for a condensate formed in a three-dimensional photonic-
crystal lower-polariton band, we eliminate the massive density and reservoir modes and obtain an effective $3+1$-dimensional KPZ equation for the condensate phase. Numerical simulations of both the KPZ equation and the full driven-dissipative polariton model show an intermediate-asymptotic regime in which the first-order coherence obeys $-\ln |\gone(0,\Delta t)|\propto |\Delta t|^{2\beta}$ and $-\ln |\gone(\Delta r,0)|\propto |\Delta r|^{2\chi}$, with exponents consistent with the $3+1$ KPZ
benchmarks $\beta= 0.1845$, $\chi= 0.3135$. Our results identify three-dimensional polariton
crystals as a controllable
quantum fluid route to higher-dimensional nonequilibrium universality.
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All authors Junhui Cao, Denis Novokreschenov, Artem Alexandrov, Timothy Halpin-Healy, Alexey Kavokin
Strongly Correlated Electrons
Thermal spin transport in easy-planar $d$-wave altermagnets controlled by magnetic field
Yuliia I. Gusieva, Kostiantyn V. Yershov, Jeroen van den Brink et al. (+1 more)
Altermagnets constitute a novel class of collinear
spin-compensated materials in which
magnon branches are
spin-split even in the non-relativistic limit. The latter is the result of a more complex
symmetry operation (compared to conventional antiferromagnets) that connects the two sublattices. Altermagnetic splitting strongly affects the
magnon transport properties, leading, in particular, to the thermal
magnon splitter effect in easy-axial $d$-wave altermagnets. Whether this effect also appears in easy-planar systems is not obvious, since the
magnon branches do not carry a constant
magnetic moment in this case. Here, we consider the easy-planar $d$-wave altermagnet of a rutile-type, e.g., NiF$_2$, and demonstrate the emergence of the altermagnetically generated
magnon magnetic moment, which is momentum-dependent and possesses $d$-wave
symmetry. This then leads to the
spin-splitter effect, i.e., the emergence of a
magnon-driven
spin current (the flow of
magnetic moment) in response to the applied temperature gradient. We also demonstrate that the corresponding thermal
spin conductivity can be effectively tuned by an external
magnetic field perpendicular to the easy plane.
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All authors Yuliia I. Gusieva, Kostiantyn V. Yershov, Jeroen van den Brink, Volodymyr P. Kravchuk
Materials Science · Cross-listed from physics.optics
Spin-canting-induced Giant Nonlinear Optical Magnetochirality in a 2D Ferrotoroid
Shian Xia, Sheng Liu, Wenhe Jia et al. (+9 more)
Achieving magnetically switchable
chiral light emission is an important goal for 2D opto-spintronics. However, conventional strategies face a fundamental trade-off between dynamic tunability and polarization contrast. Nonlinear optics, particularly the emerging mechanism of
chiral second-harmonic generation (SHG), offers a distinct strategy to bypass this restriction, yet its experimental realization remains elusive due to stringent
symmetry requirements. Here, we report
giant nonlinear optical magnetochirality in a centrosymmetric 2D ferrotoroid,
bilayer (2L) CrSBr. We reveal that a field-induced
spin-canting state breaks the parity-time (PT)
symmetry of the unperturbed
antiferromagnetic (AFM) ground state, activating a
spin-chirality-driven i-type susceptibility. The coherent interference between this emergent i-type and intrinsic c-type SHG susceptibilities generates a macroscopic circularly polarized SHG signal whose helicity is magnetically switchable. Leveraging this sensitive mechanism, we uncover remanent
magnetic states after field saturation that evade conventional linear probes. By exploiting the non-
volatility of these states, we demonstrate magneto-optical
memory and logic operations. Our work establishes a general
symmetry-driven strategy for tailoring nonlinear magnetochirality, while providing a sensitive optical probe for subtle
spin textures in the 2D limit.
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All authors Shian Xia, Sheng Liu, Wenhe Jia, Fanglu Qin, Xuanji Wang, Haixiang Luo, Yue Sun, Vanessa Li Zhang, Wenduo Chen, Jiazheng Qin, Cheng-Wei Qiu, Ting Yu
Statistical Mechanics · Cross-listed from quant-ph
Scaling theory of decoherence in Dicke superradiance
Nico S. Bassler, Julian Lyne and Javier Cuerda
The survival of many-body coherence depends on the competition between correlation buildup and decoherence. In Dicke superradiance, collective emission builds up correlations, producing a peak intensity scaling as $N^2$ for $N$ emitters. We develop a scaling theory including local dephasing and spontaneous emission and obtain fully collective, partially collective, and independent-emitter scaling regimes. The boundary of the fully collective regime defines a continuous phase transition in a transient observable. Local decoherence can prevent $N^2$ scaling despite increasing $N$.
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Strongly Correlated Electrons
Many-Body Amplification of Ligand Instabilities Driving Verwey-Type Transitions in Altermagnet CsCr$_2$S$_2$O
Xiuhua Chen and Yilin Wang
Altermagnet CsCr$_2$S$_2$O undergoes a Verwey-type metal-to-
insulator transition (MIT), accompanied by a
lattice distortion and stripe charge order on the Cr sublattice. Intriguingly, the atomic distortions occur exclusively at the ligand sites rather than the Cr sites, leaving the origin of the pronounced Cr charge disproportionation unresolved. Using density functional theory plus dynamical mean-field theory (DFT+DMFT) calculations, we identify an orbital-selective Mott state in which the correlated metallic $d_{yz}$ orbital governs the low-energy physics. We show that S-site distortions produces only a small bare charge asymmetry between the Cr sublattices through Cr-$d_{yz}$–S-$p$ hybridization. Dynamical electronic correlations, however, dramatically amplify this asymmetry, producing pronounced differentiation in both the charge occupancy and correlation strength of the $d_{yz}$ orbitals. The resulting site-dependent
spin polarization ultimately drives the MIT. In contrast, replacing S with Te substantially weakens this correlation-amplification effect and preserves a metallic state. Our work reveals a hidden, correlation-amplified feedback loop between ligand instabilities and electronic
symmetry breaking in this altermagnetic family, highlighting ligand engineering as an effective route toward robust metallic altermagnetism.
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Materials Science
Mapping the influence of symmetry breaking in structure-property relationships of ABO$_3$ perovskites
Panupol Untarabut, Sylvian Cadars, Fabien Pascale et al. (+5 more)
Perovskite
oxides have emerged as an important class of material with promising energy applications owing to their compositional and structural flexibility, which enables stabilization of both low- and high-
symmetry phases and gives rise to diverse physical properties. Under ambient conditions, most perovskites adopt low-
symmetry structures characterized by octahedral tilting and B-site displacements. Despite their importance, computational studies have largely focused on the ideal cubic phase as modeling these distortions remains challenging. The difficulty stems from the absence of a quantitative framework capable of capturing composition-dependent distortions that can occur through multiple non-equivalent atomic displacement modes, often requiring computationally expensive large supercells to explore the structural landscape. Consequently, the influence of distortions on the stability and properties of low-
symmetry perovskites remains insufficiently understood. In this work, we develop an efficient computational framework for the rapid construction and exploration of composition-dependent structural models across both low- and high-
symmetry phases. Using $\textit{symmetry constrained templates}$ and $\textit{unconstrained supercell templates}$, we systematically investigate 15 representative compositions to uncover relationships between composition, supercell size and shape, and distortion patterns. Based on these insights, we propose a robust and computationally inexpensive protocol for rapid structural exploration and assess the influence of different distortion modes on key physical properties.
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All authors Panupol Untarabut, Sylvian Cadars, Fabien Pascale, Sébastien Lebègue, Olivier Masson, Samuel Bernard, Assil Bouzid, Santanu Saha
Materials Science
PASS: Perturbation augmented space group structure sampling for transferable Fe-O machine learning interatomic potential
Zixiong Wei, Fei Shuang and Poulumi Dey
Accurate atomistic modelling of iron (Fe) oxidation requires a reliable interatomic potential, which necessitates an extensive and representative first-principles
dataset for training the interatomic potential. However, Fe-oxygen (O) system is known for its structural and
magnetic complexity, rendering the generation of high-quality
dataset challenging. In this work, we propose the Perturbation Augmented Space group structure Sampling (PASS) method to generate extensive and representative
dataset consisting of small-
cell structures with less than 10 atoms. We present a systematic approach to developing a first of its kind transferable machine learning interatomic potential (MLIP) for Fe-O system based on the atomic cluster expansion (ACE) framework. We thoroughly validate the accuracy and capability of the ACE MLIP across both pure Fe and Fe-O systems through bulk, surface, and interface properties. We showcase the formation of FeO-like structure in large-scale Fe oxidation simulation using the ACE MLIP. This work demonstrates that the PASS method yields an accurate and transferable MLIP which is capable of capturing the reactive complexity of
oxide growth while remaining computationally practical for extended systems.
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Quantum Gases
Observation of Moiré Time Crystal in Floquet-driven Rydberg Atomic Gases
Shuai Shi, Dong-Yang Zhu, Yu Yang et al. (+8 more)
A Moiré time
crystal is a non-
equilibrium quantum phase emerging from the coherent interference of two distinct frequencies, at least one being the intrinsic oscillation of a
symmetry-broken time
crystal. Its hallmark is an ultra-long beat period, reflecting a time-domain mapping of the Moiré fringes that arise from mismatched spatial
lattices. However, to date, no experimental realization of such a Moiré time
crystal has been reported. In this work, by applying a bichromatic driving field with two distinct frequencies, we demonstrate that the interplay between long-range Rydberg interactions and dissipation gives rise to a unique comb-like Moiré pattern characterized by a beat-note comb, which superimposes subharmonic periodicity and fundamental frequencies. This Moiré pattern formed by two mismatched drives is staggered in the spectrum as the frequency of one driver changes. We experimentally map the phase diagram of the system and identify a robust region where the Moiré temporal order persists against perturbations in
laser detuning. The reported Moiré time
crystal not only provides a controllable platform for exploring emergent slow-fast dynamics and synthetic space-time
symmetries but also opens avenues for engineering complex temporal order in driven
quantum many-body systems.
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All authors Shuai Shi, Dong-Yang Zhu, Yu Yang, Chu-Rong Pan, Jing-Wen Tang, Ya-Peng Zhang, Yan-Li Zhou, Wei-Tao Liu, Li-Hua Zhang, Bang Liu, Dong-Sheng Ding
Statistical Mechanics
Mpemba effect in a chemomechanical model of the Kinesin molecular motor
Karthik Cheruvary and Arnab Pal
The Mpemba effect, wherein a system prepared farther from
equilibrium relaxes faster than one initially closer to
equilibrium, has been extensively investigated in a wide range of physical systems. In contrast, its role in biologically relevant non-
equilibrium processes remains largely unexplored. Here, we investigate anomalous relaxation in the six-state chemomechanical network model of the Kinesin molecular motor under both
equilibrium and non-
equilibrium conditions. We first establish the existence of the Mpemba effect in chemical
equilibrium and show that many of its qualitative features can be understood from the underlying free-energy landscape. We then examine the effects of mechanical and chemical driving, showing that breaking detailed balance primarily reshapes the Mpemba phase diagram without qualitatively altering the relaxation phenomenology over the physically relevant parameter regime. Finally, we demonstrate that the relaxation of the motor velocity also mirrors the anomalous relaxation of the underlying
stochastic dynamics, thereby identifying an experimentally accessible signature of the Mpemba effect. Our results establish molecular motors as a promising baseline for studying anomalous relaxation in living systems and suggest a broader framework for exploring the Mpemba effect in non-
equilibrium biochemical networks.
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