Materials Science
Modelling magnetic material properties with uncertainty-aware neural networks
Clemens Wager, Heisam Moustafa, Alexander Kovacs et al. (+10 more)
Machine learning is increasingly used to accelerate materials discovery across large compositional and structural design spaces, but limited and heterogeneous data make reliable uncertainty estimation essential. In this work, we investigate uncertainty quantification for permanent magnet modeling across three complementary studies. First, on a public Curie temperature surrogate
dataset, we
benchmark Gaussian process regression, random forest bagging, and dropout-based
Bayesian neural networks and show that calibration, sharpness, and confidence curve diagnostics reveal differences in uncertainty quality that are not visible from point-prediction metrics alone. Second, we transfer this framework to the prediction of intrinsic
magnetic properties in Nd2 Fe14 B-based magnets. Third, we extend the same uncertainty-aware perspective to coercivity prediction from microstructural information using a graph neural network. Together, these studies show that uncertainty quantification improves the trustworthiness of
magnetic material property predictions and can be transferred from composition-based surrogate models to more complex structure-sensitive learning tasks.
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All authors Clemens Wager, Heisam Moustafa, Alexander Kovacs, Qais Ali, Harald Oezelt, Hayate Yamano, Masao Yano, Noritsugu Sakuma, Hyuga Hosoi, Akihito Kinoshita, Tetsuya Shoji, Akira Kato, Thomas Schrefl
Mesoscale and Nanoscale Physics
Ferroelectric Altermagnetic Chern Insulator in magnetic field: electrical control of the Chern number
Meysam Bagheri Tagani and Carmine Autieri
We investigate electrically controllable Chern
topology in a two-dimensional compensated (d)-wave altermagnet described by a
lattice-regularized Bernevig–Hughes–Zhang model. In the altermagnetic reference state, the two Kramers sectors acquire momentum-dependent
spin splitting and opposite sector Chern numbers, while the combined $C_{4z}\mathcal T$
symmetry enforces a vanishing total charge Chern number. We show that this hidden topological structure can be activated by orbital-selective
magnetic coupling and independently tuned by ferroelectric orbital hybridization. The
magnetic coupling removes the sector cancellation and generates $C=\pm1$ and $\pm2$ phases, whereas the polar distortion shifts the Dirac gap closing away from high-
symmetry momenta and enables electrical transitions such as $C=0\rightarrow-1$ and $C=1\rightarrow2$. The resulting phases exhibit the expected
chiral edge-state multiplicity and quantized anomalous
Hall conductivity. Their
topology is further reflected in the orbital magnetization through the in-gap relation $\partial_\mu \widetilde M_z=-C$. Finally, we show that the Chern phases remain robust against transverse Kramers-sector mixing and
symmetry-allowed inversion-asymmetric
spin–orbit coupling. These results establish a
symmetry-based route to electrically tunable Chern insulating phases in compensated altermagnets.
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Soft Condensed Matter
Pinned Boundaries Delay Contraction and Shape Stress Relaxation in Active Gels
Aniket Marne, James Clarke, Aravind Rao et al. (+6 more)
Cells dynamically generate, transmit, and dissipate stress. Central to these processes is the actomyosin cortex, an active contractile material that drives cellular mechanical behavior. While prior studies have focused on freely contracting actomyosin systems, the role of mechanical constraints such as adhesion to boundaries remains less explored. To address this, we employ reconstituted actomyosin gels to investigate cellular contractility. We study contraction dynamics under pinned boundary conditions, where the gel is adhered transversely to two opposing surfaces, mimicking supracellular actomyosin networks in tissues and embryos. We find that pinned contraction leads to stress buildup, delaying contraction, producing intermittent dynamics, and generating spatially nonuniform strain fields. Stress is relieved through several pathways, including active-stress-driven symmetric constriction and defect-driven processes such as boundary detachment and internal rupture. We develop a hydrodynamic model incorporating elastic, viscous, and active stress contributions that distinguishes between stress-accumulation and stress-release phases and links variations in active stress to the observed intermittent dynamics. The model predicts distinct energy relaxation rates before and after detachment events, providing insight into stress dissipation. We compare experiments with numerical simulations, which reproduce the observed behavior and reveal how internal energy is generated and dissipated during stress buildup and relaxation. Together, our results demonstrate how boundary conditions and spatial heterogeneity govern the mechanical behavior of contractile active gels. These findings provide insight into stress regulation in cellular and tissue-scale systems and may inform the design of adaptive soft materials and bioinspired robotic systems.
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All authors Aniket Marne, James Clarke, Aravind Rao, Hyunjae Lee, Kyla Wong, Aditya Sriram, Rae Robertson-Anderson, Moumita Das, José Alvarado
Materials Science · Cross-listed from physics.geo-ph
Breakdown of the classical rupture theory and earthquake propagation in the "forbidden" super-Rayleigh range
Anna Pomyalov, Fabian Barras and Eran Bouchbinder
Earthquakes propagating faster than the shear wave-speed are commonly thought to undergo a super-shear transition upon which they discontinuously jump from the sub-Rayleigh regime to the super-shear one. The super-Rayleigh regime, i.e., the range of propagation speeds between the Rayleigh and shear wave-speeds, is regarded as "forbidden" by the two-dimensional classical rupture theory. Here, we revisit the assumptions underlying the classical theory and develop a rupture theory that takes into account the dependence of the fault strength (frictional resistance) on the slip rate. The theory quantitatively agrees with numerical simulations nearly up to the Rayleigh wave-speed. Yet, very close to the latter, two-dimensional rupture solutions change their character due to frictional rate nonlinearity and rupture continuously propagates through the "forbidden" super-Rayleigh range into the super-shear regime, without a sharp super-shear transition. These results demonstrate that frictional rate dependence, generically observed in experiments, can have profound implications for fast earthquake propagation.
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Soft Condensed Matter
On the flash temperature in accelerated sliding contacts
B.N.J. Persson
The temperature increase in the contact regions between solids in sliding contact can easily reach several hundred Kelvin and thereby dramatically affect friction and wear. Here I extend an earlier multiscale theory for the flash temperature (Ref. \cite{MP}) to the case of accelerated motion, and present numerical results illustrating the theory.
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Soft Condensed Matter
Nonlinear Mechanics and Predictable Bifurcation of Multi-Cell Kresling Origami Chains
Songlin Yue, Leo de Waal, David Garcia Cava et al. (+1 more)
Meta-structures that display axial-twist coupling can be achieved through the emerging kinematics in Kresling origami patterns. A central challenge in these structures is understanding their nonlinear mechanical behaviour, specifically their
equilibrium branches and bifurcation diagrams. This involves identifying relationships between desired responses and the
geometric variables that define the design space, including the Kresling polygon count, initial twist angle, height, radius, and crease lengths. As the number of constituent units increases in an n-layer chain, we track complex
equilibrium branches extending into the post-critical regime under successive instabilities, including branch-point bifurcations and limit-point instabilities. This work begins by establishing the relationship between the
geometric design variables and the response curves of the assembled chain by modelling the crease lines as axial-load-carrying elements. Subsequently,
equilibrium branches and instabilities are systematically investigated via continuation and bifurcation analysis, beginning with the single-layer system and progressively extending to two- and three-layer configurations. Finally, a generalisation strategy is proposed to extend these findings to an n-layer Kresling chain. This strategy enables the predictive construction of
equilibrium paths and the inverse design of multi-layer meta-structures, using prescribed critical points to control post-critical behaviour. It provides a foundation for the inverse design and optimisation of architected mechanical metamaterials with programmable responses.
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All authors Songlin Yue, Leo de Waal, David Garcia Cava, Marcelo A. Dias
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Large Fluctuations in Open Quantum Systems
V. Yu. Mylnikov, S. O. Potashin and A. Kamenev
We study statistics of atypical measurement outcomes in the steady states of driven open
quantum systems. In
equilibrium, the probability distribution over the phase space, as encoded in, e.g., the Wigner function, is analytic in the phase-space coordinates. We show that this property is generically lost in driven dissipative systems: their large-deviation function develops lines and surfaces across which its derivatives are discontinuous. As an illustrative example, we consider a parametrically driven Kerr oscillator coupled linearly and/or nonlinearly to a dissipative bath. Rare fluctuations in the amplitude and phase of the induced oscillations are governed by semiclassical instanton trajectories of the corresponding Keldysh-Lindblad action. We demonstrate that a given fluctuation can be realized through multiple distinct instanton trajectories. The competition between these trajectories leads to abrupt switching of the dominant instanton and, consequently, to non-analytic features in the large-deviation function.
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Superconductivity
Mathematical Basis for Analyzing Superconducting Phase Transitions Using Catastrophe Theory
Jiu Hui Wu, Hua Tian and Kejiang Zhou
We establish a rigorous mathematical bridge from
quantum many-body path integrals to the cusp catastrophe model by Lyapunov-Schmidt reduction, which provides a theoretical foundation for analyzing superconducting phase transition using the catastrophe theory. First, it is proved that, near the critical point the infinite-dimensional effective action is diffeomorphic to a finite-dimensional catastrophe. Secondly, starting from Ginzburg-Landau free energy functional, the Euler-Lagrange partial differential equation can be reduced to the cusp catastrophe model. Thirdly, the fermionic imaginary-time path integral to the cusp catastrophe is derived through the Hubbard-Stratonovich transformation, Matsubara frequency expansion, and Grassmann
algebra. Furthermore, we connect this framework with the adsorption potential theory we proposed, elucidating the catastrophic topological nature of the electron pairing mechanism in high-temperature superconductivity. The precise microscopic derivation of the adsorption potential from first-principles electronic structure calculations would strengthen the predictive power of the theory.
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Soft Condensed Matter
Shape-space dynamics and geometric pattern formation in nonreciprocal slender bodies
Balázs Németh, Mohamed Warda and Ronojoy Adhikari
Nonreciprocal interactions in active solids violate action-reaction
symmetry and produce a net response to strain. Assuming invariance under Euclidean
symmetries, we derive a shape-space formulation for the elastohydrodynamics of nonreciprocal slender bodies that separates intrinsic deformation from rigid motion. The resulting nonlinear reaction-advection-
diffusion system represents a
geometric flow whose activity-driven instabilities generate steady, oscillatory, and chaotic patterns. These manifest as rigid, swimming, and chaotic motion, linking nonreciprocal elastohydrodynamics to
geometric pattern formation and unifying recent observations in slender active structures.
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Materials Science
Bulk-like Compressibility of the Au-Au Metallic Bond in the Atomically Precise $\mathrm{Au}_{25}$ Cluster
Camino Martín-Sánchez, Khadijetou Ahmed Ethmane, Nicholas Giamboni et al. (+3 more)
We present a high-pressure single-
crystal X-ray diffraction study of the atomically precise $\mathrm{Au}_{25}(\mathrm{PET})_{18}^{q}$ cluster ($q=-1,0$) up to 10 GPa under strictly hydrostatic conditions. Our crystallographic analysis provides direct evidence for the pressure-induced phase transitions previously suggested by spectroscopic studies. Structural refinements reveal that the cluster accommodates compression through the reorganization of the flexible ligand shell and secondary distortions of the staple motifs, while the $\mathrm{Au}_{13}$ icosahedral core remains intact. Notably, the internal Au-Au distances exhibit a monotonic contraction that quantitatively mirrors the compressibility of bulk gold. This invariant
rigidity at the sub-nanometer scale demonstrates that the fundamental stiffness of the metallic bond is preserved regardless of size. Our findings reconcile previous contradictions in the elasticity of metal nanostructures by isolating the intrinsic mechanical response of the gold kernel from extrinsic structural and experimental artifacts.
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All authors Camino Martín-Sánchez, Khadijetou Ahmed Ethmane, Nicholas Giamboni, Latévi Max Lawson Daku, Céline Besnard, Thomas Bürgi
Mesoscale and Nanoscale Physics
Berry-phase-based Topological Charge in Quasicrystals and their Observable Features in Photonic System
Ziyi Chen, Jinyu Zou, Jinhua Gao et al. (+1 more)
Topological charges based on Berry phase play the fundamental role in the topological physics. However, such topological charges remain unexplored in quasicrystals, impeding the systematic understanding of topological states in such quasiperiodic systems. In this work, by deriving all the allowed topological charges according to group representation theory and the corresponding low-energy effective
Hamiltonians, we establish a universal framework for Berry-phase-based topological charges in two-dimensional quasicrystals. Taking the $C_{8v}$ quasicrystal as an example, we demonstrate and characterize a higher topological charge of $C=4$, which is inaccessible in conventional periodic systems. Applying our framework to photonic quasicrystals, we uncover that the circling of
photon momentum around the charge gives a $C$ times winding of the electromagnetic field distribution pattern. Such observable feature provides a direct experimental method to probe the topological charges. Our work paves the way for exploring topological charges in quasiperiodic matter, and fundamentally bridges periodic and quasiperiodic topological band theories.
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All authors Ziyi Chen, Jinyu Zou, Jinhua Gao, Gang xu
Statistical Mechanics
A stochastic model for elastoplastic contact of rough surfaces incorporating scale-dependent hardness
Yang Xu, Hengxu Song and Jianqiao Hu
The stress concentrations caused by inherent roughness of natural and manufactured surfaces often induce plastic deformation at contact interfaces, a challenge compounded by competing influences of the size effect of plastic deformation and self-affine rough surface topography. To address this, we developed a novel methodology based on
stochastic theory using compounded Chapman-Kolmogorov equations, for the first time, to solve elastoplastic contact problems involving scale-dependent hardness. Our approach formulates three integral equations describing the
evolution of probability density functions of elastic contact pressure, relative plastic contact area, and relative non-contact area across geometrical scales. We thoroughly investigate the effects of scale-dependent hardness on contact pressure distribution, relative elastic and plastic contact areas, and the area-to-load relationship. By adjusting various mechanical and material properties, our model predicts a smooth transition from linear elasticity to elastic-plastic behavior and finally to full plasticity. A key advancement is the derivation of a new topographic yield parameter incorporating a wider range of material and geometrical properties, aiding identification of contact status. Numerical solutions enable highly precise determination of elastic and plastic limits via curve-fitting, and we also provide a new diagram for rapid identification of contact status. This study pioneers a
stochastic process framework for applying the compounded Chapman-Kolmogorov equation to rough surface contact analysis, and the integral equations characterizing how interfacial properties evolve with scale could offer valuable insights for other multidisciplinary fields where multiscale roughness is critical, such as earthquakes, electrical contact, and contact electrification.
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Mesoscale and Nanoscale Physics
Spin-Orbit Torque and Magnetization Switching in 2D Ferromagnetic Devices
Bao-Huei Huang, Hong Guo and Yu-Hui Tang
Current-induced
spin-orbit torque has emerged as a powerful technique for manipulating magnetization switching of ferromagnet/nonmagnet (FM/NM) based
memory cell. By investigating nonequilibrium
spin torque effect in a van der Waals heterobilayer, trigonal $\text{Cr}_{3}\text{Te}_{4}/\text{PtTe}_{2}$, the first-principles
quantum transport calculations are applied to determine both local
spin induction, resulting from Rashba-Edelstein effect in the FM layer, and
spin current injection, flowing from the NM to the FM layer. Our work reveals that local
spin induction significantly generates the fieldlike torque, which primarily governs the switching current in systems with strong in-plane
magnetic anisotropy. Our work emphasizes the importance of optimizing
spin Hall effect in the NM layer for perpendicular
magnetic anisotropy (PMA)-based magnetization switching and maximizing the Rashba effect in the FM layer for in-plane
magnetic anisotropy (IMA)-based switching.
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Superconductivity
Ambient and Pressure Dependent Superconductivity with Hydrogen Storage Potential in Quaternary Hydride LiMgZr2H12: A Comprehensive First-principles Insights
Jubair Hossan Abir, Tauhidur Rahman, Salauddin Muhammad Anis et al. (+2 more)
Molecular hydrides have attracted relatively less
attention in the search for high Tc
superconductors because their hydrogen quasi-molecular units tend to be electronically inactive for superconductivity. In contrast, hydrogen rich compounds under high pressure have been widely considered strong candidates for achieving room-temperature superconductivity. However, their dependence on extreme pressure conditions significantly constrains their practical applicability. This work investigates hydrogen-rich superconducting materials that may be stable under ambient pressure conditions. Motivated by recent studies on the MgZrH2n family, a LiMgZr2H12 structure with Pmmm
symmetry was designed. The mechanical, thermodynamic, and dynamical stability of the compound, together with its electronic and optical properties, were systematically investigated using first-principles calculations. Li doping in LiMgZr2H12 significantly increases the hydrogen derived contribution near the
Fermi level (EF) and strengthens the electron-
phonon coupling constant ({\lambda}) compared with MgZrH6. LiMgZr2H12 exhibits a critical temperature of 72.76 K at ambient pressure, which is further enhanced by applying pressure. At 10 GPa the critical temperature increases to 77.3 K. Elastic property analysis shows that the material remains mechanically stable over the pressure range studied (0-10 GPa). It also behaves like a ductile material suitable for current carrying applications. The material has a high machinability index, which is much higher than that of stainless steels. In addition, LiMgZr2H12 exhibits a gravimetric hydrogen storage capacity of 5.36 wt%, indicating its potential as a promising candidate for hybrid hydrogen storage technologies. This work offers a new direction for designing high-Tc hydrides at ambient conditions.
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All authors Jubair Hossan Abir, Tauhidur Rahman, Salauddin Muhammad Anis, Saleh Hasan Naqib, Raihana Shams Islam
Materials Science
Integrated magnonic neural circuits based on nonlinear wave neurons
Mengying Guo, Xudong Jing, Kristýna Davidkova et al. (+11 more)
Artificial intelligence is driving intense interest in alternative computing hardware capable of neural information processing beyond conventional charge-based electronics. Among emerging approaches, wave-based computing promises highly parallel and energy-efficient operation, but scalable physical neural hardware has remained elusive because wave systems generally lack cascadable nonlinear
neurons with signal regeneration and phase-robust operation. Here we demonstrate integrated magnonic neural
circuits based on nonlinear threshold
neurons realized in nanoscale yttrium iron garnet waveguides. The
neurons perform weighted summation of multiple
spin-wave inputs, while a pump-controlled nonlinear activation defines continuously tunable firing thresholds. Owing to deeply nonlinear
spin-wave dynamics, the activated
neurons emit self-normalized outputs whose intensities are largely independent of the input amplitudes, while nonlinear phase self-adjustment suppresses sensitivity to the relative input phases, enabling deterministic
neuron-to-
neuron cascading without external signal restoration. We experimentally realize programmable threshold
neurons, reconfigurable weighted classification and deterministic cascading between sequential neuronal stages, and further demonstrate reconfigurable physical pattern recognition in a seven-
neuron integrated magnonic
circuit through experimental classification of the binary letter patterns 'HUST'. These results establish nonlinear
magnons as a scalable platform for integrated neural hardware and position nonlinear wave dynamics as a general paradigm for physical neuromorphic computing.
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All authors Mengying Guo, Xudong Jing, Kristýna Davidkova, Roman Verba, Zhenyu Zhou, Xueyu Guo, Carsten Dubs, Chuan Gao, Yiheng Rao, Kaiming Cai, Jing Li, Philipp Pirro, Andrii V. Chumak, Qi Wang
Materials Science
Observation of coherently modulated thermal phonon band and lifetime in superlattice
Yuxuan Liao, Hiroshi Uchiyama, Naomi Nagai et al. (+12 more)
Manipulating
phonon band structures through wave interference in artificial periodic nanostructures is of fundamental interest and forms the foundation of
phonon band engineering. Yet, direct observation of thermal
phonon wave interference has remained elusive despite half a century of extensive research. Here, utilizing inelastic x-ray scattering, we directly observed momentum-resolved coherently modulated thermal
phonon bands and lifetimes in a short-period GaAs/AlAs superlattice at 300 K. The modulation persists at even 500 K, demonstrating robust coherent thermal
phonon transport at high temperatures. Our measurements, combined with ab initio
lattice-dynamics calculations, further show that thermal
phonon interference expands the three-
phonon scattering phase space and strengthens anharmonic effects, highlighting the interplay between
phonon band modulation and anharmonicity. Our observations establish nanostructuring as a versatile route for engineering thermal
phonon bands and lifetimes at high temperatures across diverse applications.
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All authors Yuxuan Liao, Hiroshi Uchiyama, Naomi Nagai, Natalia Morais, Taiushun Manjo, Rulei Guo, Harsh Chandra, Ryohei Nagahiro, Bin Xu, Hiroshi Fukui, Daisuke Ishikawa, Alfred Q.R. Baron, Yasuhiko Arakawa, Kazuhiko Hirakawa, Junichiro Shiomi
Mesoscale and Nanoscale Physics
DSpinGNN: A Physics-Informed Equivariant Graph Neural Network for Dynamic Magnetic Exchange Prediction in Strain-Deformed Monolayer CrI$_3$
Isam A. Balghari, M. Faryad and M. Sabieh Anwar
Resolving the instantaneous, position-dependent isotropic
magnetic exchange coupling $J_{ij}$ across a dynamically deforming
crystal lattice requires a computational approach that simultaneously handles structural forces and
magnetic interactions at length scales inaccessible to first-principles methods. Here we introduce DSpinGNN, a bifurcated machine-learning architecture comprising an $E(3)$-equivariant graph neural network (E-GNN) for classical Langevin structural dynamics and a physics-informed $\Delta$-MLP that maps instantaneous local Cr-I-Cr bond geometry to isotropic exchange couplings, with the Goodenough-Kanamori superexchange relationship embedded as an analytical inductive bias. Trained on 345 DFT+U configurations of monolayer CrI$_3$ and evaluated on a strictly withheld 61-configuration test set, DSpinGNN simultaneously achieves an energy MAE of $1.1$ meV/atom, a force MAE of $6.5$ meV/Å, and an exchange coupling MAE of $0.18$ meV ($R^2 = 0.91$). Deployed at 400$\times$ scale in a 3,200-atom supercell under a collinear Ising-constrained adiabatic approximation at $5$ K, the model maps the local exchange response to a propagating biaxial strain wave. Wave reflection at periodic boundaries generates transient constructive interference regions where local compressive strain exceeds the DFT-established FM-to-AFM threshold, producing spatially heterogeneous exchange coupling textures that damp as the wave dissipates. Quantitative analysis yields a domain wall width of $\xi = 1.7 \pm 0.3$~nm and a constructive-interference oscillation period of $\tau = 0.27$~ps – mesoscopic observables inaccessible to direct DFT and constituting testable predictions for cryogenic
magnetic force microscopy. DSpinGNN provides a reproducible, transferable framework for mesoscale exchange mapping in strain-driven 2D
magnetic materials.
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Mesoscale and Nanoscale Physics
Consistent Evaluation of Operators Involving the Position Operator in the Bloch Representation: Application to the Orbital Moment
Daehyeon An, Junmo Jeon and Se Kwon Kim
The position operator plays a central role in condensed-matter observables such as velocity, orbital moment, and electric polarization. In solid-state physics, the evaluation of operators incorporating the position operator has not reached a consensus, as observed in the operator-level discrepancy between the local circulation of Wannier functions and the self-rotation of wave packets. Here, to achieve a consistent evaluation of such operators, we propose three rules for evaluating operators involving the position operator in the Bloch representation. The rules are devised to satisfy physical conditions: independence from the choice of unit
cell, preservation of Hermitian conjugacy for the product of operators, and recovery of the correct intraband velocity. We further address the gauge dependence of the position operator and introduce a scheme termed gauge filtration, which systematically removes gauge-dependent contributions from the operators containing the position operator. This methodology ensures that the quantities obtained from the operator evaluation correspond to observable physical phenomena. By applying our framework, we reconcile the results concerning the self-rotation of the wave packet and the local circulation of the Wannier function. We expect our proposal to establish a consistent framework for evaluating operators involving the position operator.
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Soft Condensed Matter
A quantitative approach to flowing supercooled liquids: From microscopic heterogeneities to rheology
Dong-Xu Yu and Zhe Wang
Soft glassy materials display rich and complex flow behaviors across both macroscopic and molecular scales, and a fundamental understanding of these phenomena remains an outstanding challenge. Here, we propose a theoretical model for the flow of supercooled
liquids – a typical class of glassy fluids – based on a two-state paradigm that conceptualizes the flow as a dynamic coexistence of transient solid-like and
liquid-like regions. The model rests on two essential physical ingredients: a correlation length that captures medium-range structural order, and a localized elasticity-mediated interaction that restricts stress propagation within solid-like regions. Remarkably, with all parameters determined solely from
equilibrium state, the model quantitatively reproduces rheological responses – including both steady-state and start-up shear – for a broad range of shear rates. Furthermore, it simultaneously captures the
evolution of molecular dynamic heterogeneity. This dual success – spanning macroscopic rheology and microscopic spatiotemporal fluctuations – underscores the pivotal role of structural and dynamic heterogeneities in governing the rheological response. Moreover, it provides a direct understanding of how the flow behaviors of a supercooled
liquid are embedded in its
equilibrium properties.
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Materials Science
Unveiling Orbital-mediated Ultrafast Demagnetization in Rare Earth-Transition-Metal Ferrimagnets
Jianwen Gao, Linlin Zhang, Mingli Ge et al. (+12 more)
The ultimate speed limit of
magnetic recording and spintronic devices is set by the efficiency of angular-momentum transfer during ultrafast demagnetization, yet its microscopic pathway in Rare-Earth-Transition-Metal (RE-TM) ferrimagnets remains debated. Here, we establish an orbital-mediated framework in which 3d
spin-orbit coupling (SOC) governs angular momentum (AM) dissipation. Strong 3d-SOC in RE-Co enables sub-picosecond, single-step demagnetization via direct orbital-to-
lattice transfer, whereas weak 3d-SOC in RE-Fe redirects AM into 4f orbitals, producing slower two-step dynamics. The second-stage rate scales with 4f-SOC strength, revealing a distinct orbital-mediated dissipation channel. Using time-resolved magneto-optical Kerr measurements, supported by an extended four-temperature model, corroborate this picture across diverse RE-TM systems (RE = Sm, Gd, Tb, Dy, Ho and TM = Fe, Co, CoNi). Our results identify the SOC-driven competition between 3d and 4f orbital channels as the universal mechanism governing ultrafast demagnetization in RE-TM ferrimagnets, enabling rational design of the switching speed for next-generation spintronic devices.
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All authors Jianwen Gao, Linlin Zhang, Mingli Ge, Runhua Zhang, Jinshan Wang, Hui Li, Xiaowei Zhou, Zhu Liu, Zongzhi Zhang, Li Xi, Yalu Zuo, Chenglong Jia, Feng Qiu, Shaojie Hu, Yang Ren
Materials Science
Chiral Magnons and Cycloidal Phonons in Altermagnetic CuF$_{2}$ Monolayer
Andrea M. León, Matías F. Torreblanca, Carmine Autieri et al. (+1 more)
Altermagnetism establishes momentum-dependent
spin splitting through non-symmorphic
crystal symmetries, yet whether these same
symmetries simultaneously govern
spin and
lattice collective excitations remains open. Here we show, using first-principles calculations and linear
spin-wave theory, that monolayer CuF$_2$ hosts both chirality-split
magnons and cycloidal
phonons controlled by the same $P2_1/c$
symmetry operations. The altermagnetic order drives strongly anisotropic
magnon chirality via symmetric anisotropic exchange, with Dzyaloshinskii–Moriya interactions acting as a weak secondary modulation. Crucially, the
phonon and
magnon chiral responses are directionally complementary: cycloidal
phonon angular momentum emerges precisely where
magnon chirality is
symmetry-suppressed, and vice versa. The
magnon bands further carry quantized Chern numbers $C^M = \pm 2$, confirming non-trivial altermagnetic
topology. These results establish monolayer CuF$_2$ as a platform where a single
symmetry framework engineers magnonic, phononic, and topological responses, providing a direct connection between altermagnetism and
spin-
lattice chirality in two-dimensional materials.
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All authors Andrea M. León, Matías F. Torreblanca, Carmine Autieri, Jhon W. González
Materials Science · Cross-listed from cs.LG
Range-Aware Bayesian Optimization for Discovering Diverse Designs within Target Property Windows
Shengli Jiang, Jason Wu, Charles M. Schroeder et al. (+1 more)
In many materials and product design problems, desirable candidates exhibit properties that fall within an acceptable range rather than achieve a single optimum. Recovering multiple, distinct solutions that satisfy such specifications is also practically valuable, as some candidates may be preferred for reasons of cost, processability, or robustness that are difficult to encode directly in an objective function. Here, we develop a range-aware
Bayesian optimization (BO) framework in which the acquisition function directly scores the posterior probability that a candidate satisfies a target range. The framework naturally extends to parallel pursuit of multiple distinct specifications over a shared candidate space. Across
benchmark tasks, range-aware acquisition consistently recovers larger and more diverse sets of valid designs than standard BO baselines and recent goal-seeking methods. Its utility is further demonstrated in two practically motivated design case studies involving optimizing reaction conditions for
polymer synthesis and sequence-defined oligomer discovery for prescribed optical absorption bands, supported by
quantum chemical calculations. These results suggest that range-aware BO can provide a practical and sample-efficient foundation for specification-driven design, particularly when design flexibility and solution diversity are important considerations.
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All authors Shengli Jiang, Jason Wu, Charles M. Schroeder, Michael A. Webb
Statistical Mechanics · Cross-listed from quant-ph
Diffusive Relaxation of Participation Entropy in U(1)-symmetric Dynamics
Hanchen Liu, Tianci Zhou and Xiao Chen
Participation
entropy (PE) quantifies the spread of a many-body wavefunction across configuration space. While PE relaxes rapidly in generic chaotic systems, we show that $\mathrm{U}(1)$ conservation laws slow it down by imprinting with the slow hydrodynamic modes. Using a cluster expansion around
equilibrium, we show that, after local density inhomogeneities decay, the leading PE deficit is dominated by squared connected density correlations. The long time relaxation is therefore controlled by diffusive correlation spreading, giving $\Delta S(t)\sim t^{-1/2}$ in the hydrodynamic regime and crossing over to $\sim \exp[-O(t/L^2)]$ when $t\geq L^2$. We confirm this
entropy correlation relation using exact computation and infinite system tensor network simulations in various
quantum $\mathrm{U}(1)$ conserving
circuits. Our results establish PE as a sensitive probe of hydrodynamic
memory and suggest that slow relaxation is a generic consequence of conservation laws.
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Mesoscale and Nanoscale Physics
Polarization-Resolved Photon Statistics of Cavity Quantum Materials
Benjamin Kass, Spenser Talkington and Martin Claassen
By forming hybrid light-matter states, optical cavities offer a route for engineering material properties, however, unambiguously probing the effects of light-matter coupling remains difficult. Here, we show that the polarization-resolved statistics of
photons transmitted through a cavity, measurable via $g^{(2)}$, provide one such diagnostic. By relating $g^{(2)}$ to matter correlation functions such as the Raman structure factor, we link
photon bunching and antibunching to material properties. By applying this method to the stripy-to-
antiferromagnetic transition in the Kitaev-Heisenberg
spin model, we find that polarization-dependent patterns of bunching and antibunching encode the
magnetic point-group
symmetries of each phase and characterize the behavior at the phase boundary. Finally, we predict measuring $g^{(2)}$ for output
photon pairs polarized orthogonal to the input field will isolate higher-order light-matter scattering processes that probe higher-order material correlations.
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Strongly Correlated Electrons
Invariants of Sequential Circuits and Generalized Non-Abelian Statistics
Shintaro Sato, Yoshimasa Hidaka and Ryohei Kobayashi
Non-invertible
symmetries in
quantum many-body systems generally give rise to sequential
unitary circuits that move
symmetry defects. In this paper, we investigate invariants defined by sequences of such
circuits, which move non-invertible defects and generate a Berry phase evaluated on
quantum states with defects. We show that this Berry phase generally defines an invariant under local deformations, provided that the sequential
circuits preserve the locality of those deformations. This invariant also rules out a short-range-entangled state that preserves the non-invertible
symmetry, thereby signaling the 't Hooft anomaly of a non-invertible
symmetry purely in terms of
unitary operators acting on a state. We then apply this framework to loop excitations in three spatial dimensions and identify a new loop excitation in the (3+1)D $\mathbb{D}_4$ topological order, which we dub a non-Abelian fermionic loop. Using the invariant of sequential
circuits, we characterize the statistics of non-Abelian fermionic loops. In addition, we find a new (3+1)D mixed topological order with a single non-Abelian fermionic loop, whose long-range
entanglement is protected by an invariant of sequential
circuits.
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Superconductivity
Unveiling the Interplay of Charge and Magnetic Excitations in HgBa$_2$Ca$_2$Cu$_3$O$_{8+\delta}$
Karn Rongrueangkul, Martina Fedele, Leonardo Martinelli et al. (+10 more)
Unraveling the mechanism that binds electrons into Cooper pairs in cuprate high-temperature
superconductors remains one of the most fundamental challenges in condensed-matter physics. While both
magnetic interactions and
lattice vibrations are known to govern key electronic properties, their possible cooperation has never been directly observed. We investigate HgBa$_2$Ca$_2$Cu$_3$O$_{8+\delta}$ (Hg1223) - the cuprate with the highest $T_{\mathrm{c}}$ at ambient pressure - as a magnifying glass to probe the possible entwining of the excitations at the core of the pairing. Using resonant inelastic X-ray scattering, we find that the charge response is dominated by dynamic charge density fluctuations (CDF) extending up to several hundred meV, where
magnetic excitations reside. At the same momentum where CDF are most intense, the paramagnon energy exhibits a pronounced softening, revealing a strong interplay among charge,
lattice, and
spin excitations. Our results point to a cooperative mechanism in which dynamic charge fluctuations mediate the coupling between
lattice, charge and
spin degrees of freedom-shedding new light on the fundamental origin of high-$T_{\mathrm{c}}$ superconductivity.
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All authors Karn Rongrueangkul, Martina Fedele, Leonardo Martinelli, Giacomo Merzoni, Roberto Sant, Nicholas B. Brookes, Dorothée Colson, Alain Sacuto, Götz Seibold, Sergio Caprara, Marco Moretti Sala, Giacomo Ghiringhelli, Riccardo Arpaia