Strongly Correlated Electrons
Electronic correlations driving Chirality-Induced Spin Selectivity
Jacek Herbrych and Maria Daghofer
We explicitly account for electron-electron interactions when modeling low-dimensional helical organic molecules. We show that competition between various hopping channels, together with interaction-induced double- and superexchange mechanisms, can stabilize non-collinear helical
magnetic order. The resulting single-electron bands exhibit partial
spin polarization, a manifestation of $p$-wave magnetism. Using density-
matrix renormalization group, cluster perturbation theory, and Monte Carlo methods, we find that even vanishingly small
spin-orbit coupling triggers strong
spin selectivity at temperatures significantly above the
spin-orbit scale. While strong correlations are essential for this mechanism, long-range
spin ordering is not required. We thus propose non-collinear
spin correlations driven by Coulomb interactions as an explanation of chirality-induced
spin selectivity and discuss connections to experiments.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Heralded ultrafast generation of macroscopic quantum states in matter with bright squeezed vacuum light
Shohei Imai
We show that bright squeezed
vacuum light, combined with a single-shot quadrature measurement of the post-interaction light, enables the ultrafast generation of macroscopic
quantum states in matter. Although in the weak-coupling regime multiphoton
quantum light leaves the unconditional matter state as a classical mixture due to light–matter
entanglement, quadrature-based heralding prepares the matter in a Gaussian-weighted
quantum superposition of
laser-driven matter states. For an ensemble of resonantly electric-dipole-coupled two-level systems, this heralding dynamics acts as a Gaussian filter with respect to the electric polarization, with brighter squeezed-
vacuum light accelerating the preparation of the zero-
eigenvalue Dicke state. Counter-rotating terms further drive a stroboscopic transition from this Dicke state to a cat-like state. Our results open a route to ultrafast engineering of macroscopic
quantum matter with strong-field
quantum light.
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Mesoscale and Nanoscale Physics
Induced nonlinear phase shift of forward volume spin waves in magnetic films and one-dimensional magnonic crystals
Alexey B. Ustinov, Roman V. Haponchyk, Anton P. Burovikhin et al. (+2 more)
A differential phase shift of a low-power
spin wave (SW) induced by a high-power pumping wave co-propagating at different frequencies in perpendicularly magnetized
magnetic films has been studied. We find that this effect for forward volume SWs propagating in yttrium iron garnet (YIG) films is stronger than that for surface SWs propagating in tangentially magnetized films. The results show that the induced nonlinear phase shift up to 180{\deg} takes place for pumping wave power of a few milliwatts. The phenomenon paves the way for fast and energy-efficient control of one-dimensional
magnon transport.
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All authors Alexey B. Ustinov, Roman V. Haponchyk, Anton P. Burovikhin, Mitsuteru Inoue, Taichi Goto
Strongly Correlated Electrons
Electron momentum densities from QSGW and $G^0W^0$: Revealing the role of many-body effects within the reduced density matrix
A. D. N. James, J. A. Gould, T. M. Mason et al. (+2 more)
The ground-state many-body electron momentum density, which can be probed by x-ray Compton scattering, holds insights into the electronic structure of materials. Comparisons between the measured so-called Compton profiles and the theoretical ones are invaluable in assessing the successes and failures of the methodology used to generate the theoretical ground-state electronic structure. Here, we present calculations of the Compton profiles of Li, Si, Cr, and Ni using the state-of-the-art QSGW method within the Questaal package compared with density functional theory (DFT), one-shot $GW$ ($G^0W^0$) predictions and with experiment. This comparison reveals significant differences between the QSGW and $G^0W^0$ methods which we attribute to the distinction between the single particle density provided by the QSGW method and the many-body density that we construct from the $G^0W^0$ theory; although in general the QSGW description of the electronic structure is superior to that of $G^0W^0$, we find the use of the many-body reduced density
matrix is key to improving the agreement of the Compton profile with experiment.
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All authors A. D. N. James, J. A. Gould, T. M. Mason, J. Jackson, S. B. Dugdale
Materials Science
Role of structure and charge trapping on the bipolaron formation and magnetic-field response of gated conjugated polymers
Zuchong Yang, Vincent Lemaur, Melissa Berteau-Rainville et al. (+3 more)
Conjugated
polymers exhibit unique
spin-dependent phenomena arising from weak yet critical hyperfine interactions. Understanding these
spin effects, particularly the
spin-dependent formation and decay of correlated
spin pairs, is important for advancing both organic electronics and
polymer-based spintronics. Intrinsic
magnetic-field responses such as magnetoresistance have primarily been investigated in diode architectures, where electrons and holes coexist. However, such systems are less suitable for probing bipolaron formation in unipolar transport, and the relationship between
polymer structure and bipolaron formation in lightly doped
polymers remains unclear. Here, we systematically investigate intrinsic magnetoresistance in representative conjugated
polymers using field-effect transistors and observe a generally positive magnetoresistance. First-principles simulations reveal that bipolarons preferentially form on short conjugated segments associated with amorphous regions. Moreover, comparisons across these
polymers show that enhanced charge trapping correlates with stronger magnetoresistance, implying promoted bipolaron formation. Bipolaron-incorporated energylevel-
alignment modeling near metal/
polymer interfaces suggests that charge traps can increase the bipolaron density.
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All authors Zuchong Yang, Vincent Lemaur, Melissa Berteau-Rainville, Olivier Bardagot, Yoann Olivier, Emanuele Orgiu
Materials Science
What drives performance in molecular MPNNs? An operator-level factorial benchmark
Panyu Jiao, Shuizhou Chen, Yiheng Shen et al. (+3 more)
Message-passing neural networks (MPNNs) are widely used for molecular property prediction, but their deployment as monolithic architectures makes it difficult to identify how specific message-passing operators affect performance. We present an operator-level factorial
benchmark that decomposes 2D molecular MPNNs into the three families of message-seed initialization, node-edge fusion, and node update operators. The resulting 84 configurations are benchmarked on ten MoleculeNet
datasets under a shared experimental setup and statistical analysis protocol. Across this controlled design, performance variation is associated primarily with message construction rather than update complexity. Message-seed initialization shows significant family-level effects for both regression and classification, node-edge fusion shows a significant family-level effect for regression with descriptive advantages for concatenation-based mixing, and the update family shows no statistically supported effect for either endpoint family. A representation probe into the Quinethazone molecule further demonstrates that concatenation-based mixing can better differentiate chemically distinct heteroatoms and withstand oversmoothing than Hadamard gating. Representative configurations selected separately for classification and regression recover competitive performance relative to established molecular graph neural network (GNN) baselines, ranking numerically best on eight of ten
benchmark datasets. These empirical results are interpreted through concise mechanistic analyses of representative node-edge fusion and update operators. Our findings provide empirical design heuristics for molecular MPNNs by turning model design from a search over monolithic architectures into a targeted assessment of where and how chemical information enters the message-passing pipeline.
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All authors Panyu Jiao, Shuizhou Chen, Yiheng Shen, Yuyang Wang, Runhai Ouyang, Wei Xie
Soft Condensed Matter
Theory of distribution skewness effect on polydisperse random close packing
Vinay Vaibhav, Carmine Anzivino and Alessio Zaccone
We investigate the random close packing density, $\phi_\textrm{RCP}$, of polydisperse hard sphere systems using a theoretical framework based on the
equilibrium model of crowding. We derive a closed-form solution for $\phi_\textrm{RCP}$ in terms of the moments of the diameter distribution, enabling an analytical exploration of the effects of polydispersity ($\delta$) and skewness ($S$) on packing density. For a binary mixture, it is possible to explore a broader range of dependence of $\phi_\textrm{RCP}$ on $\delta$ for a given $S$ or on $S$ for a given $\delta$. We show that the dependencies of $\phi_\textrm{RCP}$ on skewness for a variety of continuous distributions collapse onto a theoretical master curve obtained for the binary mixture case. By correcting the theory so that it obeys known exact limiting behaviours for extreme size asymmetry, our analytical predictions not only agree with previously obtained numerical results, but also predict previously unexplored regions of the $\phi_\textrm{RCP}$ parameter space.
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Mesoscale and Nanoscale Physics
Coherent and Dissipative Spin Torques in Quantum Dots: A Unified Framework for Quantum Spin Dynamics
Dominic Ruckert, Stepan Kovarik, Richard Schlitz et al. (+4 more)
The manipulation of single
spins through
spin-polarized tunneling opens new routes for
quantum control at the atomic scale. We present a theoretical framework describing
spin-transfer,
spin torques and
spin resonance in molecular
quantum dots weakly coupled to
magnetic electrodes. By deriving a Lindblad master equation from microscopic tunneling processes, we capture both coherent exchange interactions and dissipative
spin torque effects within a unified approach. We analyze how charge transport through localized orbitals influences
spin dynamics and show that modulating the tunneling rates in time can induce electron
spin resonance. This framework is further extended to coupled
spin systems, revealing how
spin coherence and
entanglement respond to local
spin torques and highlighting sources of transport-driven decoherence. Our results provide a general model to interpret
spin-resolved tunneling experiments and extend classical
spin torque concepts into the
quantum regime.
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All authors Dominic Ruckert, Stepan Kovarik, Richard Schlitz, Mirco Grellmann, Aishwarya Vishwakarma, Pietro Gambardella, Sebastian Stepanow
Materials Science
Composition-dependent Thin-film Synthesis of Layered Ternary Iron Nitrides FeMN2 (M = W, Mo)
Baptiste Julien, Yuwei Yang, Liam A. V. Nagle-Cocco et al. (+3 more)
Ternary transition-metal nitrides with layered
crystal structure host anisotropic bonding and reduced dimensionality that may lead unconventional electronic and
magnetic behavior. The synthesis of these layered nitrides phases in thin-film form is difficult because reactive sputtering often favors metastable rocksalt-derived structures. Here we report the composition-dependent thin-film synthesis and characterization of structure and properties of layered ternary iron nitrides FeMN2 (M = W, Mo) with triangular Fe sublattice, prepared by reactive sputtering of amorphous precursors and post-deposition ammonia (NH3) annealing that staggers atomic mixing of the element precursors and long-range crystallization of extended structure. We find that FeWN2 maintains good phase purity across a broad composition range indicative of cation substitution in the layered structure, while FeMoN2 only shows good phase purity in Fe-poor composition, with an optimum corresponding to Fe0.8Mo1.2N2 stoichiometry. Azimuthal grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis shows that in both material systems, Fe-rich films exhibit strong out-of-plane fiber textures, and synchrotron X-ray absorption spectroscopy (XAS) provides insight into local Fe state and environment in both material systems. Room-temperature magnetization measurements of FeWN2 reveal that while the stoichiometric film shows a simple paramagnetic behavior, the Fe-poor films are weakly
ferromagnetic. Together, these results suggest that off-stoichiometry and local disorder within the triangular Fe sublattice may partially relieve
magnetic frustration in the layered framework, and highlight the strong coupling between composition, microstructure, and
magnetic properties in layered nitride materials.
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All authors Baptiste Julien, Yuwei Yang, Liam A. V. Nagle-Cocco, Nicholas A. Strange, Nicholas M. Bedford, Andriy Zakutayev
Mesoscale and Nanoscale Physics
Carrier-coupled ultrafast structural dynamics and interlayer energy transport of supported transition metal dichalcogenide heterostructures
Md. Shaikot Alam Shakil, Ting-Hsuan Wu, Xing He et al. (+5 more)
Understanding the electronic coupling and energy flow across layered two-dimensional
heterostructures (HSs) is crucial to the exploitation of carrier and
phonon transports as well as thermal management in next-generation optoelectronic devices. By using reflection ultrafast electron diffraction, we directly examine photoinduced out-of-plane structural dynamics of supported MoS2/WS2
bilayer HSs and their individual monolayers. Experimental evidence reveals the launch of ultrafast carrier-coupled intralayer atomic motions due to interlayer charge transfer across the van der Waals (vdW) heterojunctions that is absent for individual monolayers. Such a notable carrier-
lattice correlation is in addition to the electronic coupling manifested in the enhanced optical absorption for HSs. Also, different pathways of energy flow as a result of carrier-
phonon coupling and
phonon scattering are reported with the corresponding characteristic times. On longer timescales, relaxation of thermalized atomic motions can be sufficiently described by a thermal transport model. A higher thermal boundary conductance (TBC) across MoS2/WS2 HSs is obtained compared to those at the monolayer-substrate interfaces; however, the similar TBC values suggest comparable couplings of
phonons across vdW contacts. These results further shed light on the optical,
phonon, and interfacial thermal properties of vertically-stacked vdW HSs.
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All authors Md. Shaikot Alam Shakil, Ting-Hsuan Wu, Xing He, Abu Montakim Tareq, Zhenjia Zhou, Libo Gao, Naihao Chiang, Ding-Shyue Yang
Mesoscale and Nanoscale Physics
Engineering Quantum Criticality in the Integer Quantum Hall Regime through a Screening Layer
C. T. Tai, P. T. Madathil, A. Gupta et al. (+3 more)
Disorder-induced localization of electrons and electron-electron interaction are among the most fundamental problems in condensed matter physics. In two-dimensional electron systems, extensive studies have led to the emergence of a scaling picture, characterized by a set of universal critical exponents that govern the transitions between the integer
quantum Hall plateaus. From the temperature dependence of the plateau-to-plateau transitions, experiments primarily report k ~ 0.42, implying a dynamic exponent z = 1, consistent with a theoretical picture where electrons have a long-range (1/r) interaction. Theory also predicts that z = 2 for short-range electron interaction, but an experimental verification has remained elusive. Here, we directly probe the influence of Coulomb interaction on these transitions using a
bilayer electron system confined to a GaAs double
quantum well device. The two layers are in close proximity, with an interlayer distance approximately equal to the
magnetic length at the relevant
magnetic fields. By tuning the electron density in the top layer, we access both insulating and metallic phases of the electrons in this layer as a function of
magnetic field, allowing in-situ control of the unscreened and screened interaction strengths in the bottom layer as it goes through its plateau-to-plateau transitions. In the unscreened case, we measure k ~ 0.42 consistent with the widely reported value. More importantly, when screening is introduced, k is reduced to ~ 0.22, implying z = 2. Our results provide direct experimental evidence for the role of electron-electron interaction in determining critical behavior in the
quantum Hall regime, and demonstrate screening as a powerful tuning parameter for engineering
quantum criticality.
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All authors C. T. Tai, P. T. Madathil, A. Gupta, L. N. Pfeiffer, K. W. Baldwin, M. Shayegan
Materials Science
Towards exascale fully relativistic pseudopotential density functional theory calculations enabled by mixed-precision computation and compressed-communication using residual based subspace iteration
Nikhil Kodali, Gourab Panigrahi, Nishant Gupta et al. (+6 more)
Materials exhibiting noncollinear magnetism or strong
spin-orbit-coupling underpin many spintronic and topological applications, but their simulations require complex two-component spinors and costs substantially more than scalar density functional theory (DFT). We present a GPU-centric exascale finite-element DFT framework with noncollinear magnetism and
spin-orbit-coupling, combining (i) adaptive higher-order finite-element discretization, (ii) a
matrix-free Poisson solver, (iii) residual-based Chebyshev filtered subspace iteration (R-ChFSI) for sparse generalized eigenproblems, (iv) R-ChFSI-enabled mixed precision computation with block floating-point compressed MPI communication, and (v) communication-efficient band partitioning. R-ChFSI permits inexact
matrix-multivector products and $4\times$–$6.4\times$ compression of communicated data relative to FP64 while preserving double-precision robustness and reducing computation and data movement. Results demonstrate strong scaling on Aurora and Frontier, with up to $3.4\times$ faster Chebyshev filtering. On Aurora, total self-consistent-field (SCF) solve wall time reduces by $2\times$. An 800-node (9,600-GPU) calculation demonstrates fully relativistic pseudopotential DFT for $\sim$80,000 electrons in under 7 minutes per SCF iteration.
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All authors Nikhil Kodali, Gourab Panigrahi, Nishant Gupta, Kartick Ramakrishnan, Sundaresan G, Rudra Panch, Sambit Das, Vishwas Rao, Phani Motamarri
Statistical Mechanics
Quantum Spin-5/2 Blume-Capel Model in a Random Transverse-Crystalline Field Anisotropy
Claudio M. Salgado, Karollaine C. Leite, Thiago M. Tunes et al. (+3 more)
In this work, we investigate the thermodynamic properties of the
quantum Blume-Capel model with
spin \( S = 5/2 \) in the presence of transverse and random crystalline fields. The system is described by a
Hamiltonian that includes
ferromagnetic exchange interactions between nearest neighbors, a longitudinal single-ion anisotropy, and a transverse single-ion anisotropy. Using a mean-field approach based on Bogoliubov's inequality for the Gibbs free energy, we derive the fundamental thermodynamic potential and the equation of state for the magnetization. The influence of the longitudinal and transverse anisotropy parameters on the
magnetic ordering and phase transitions is analyzed in detail. We present magnetization versus temperature diagrams for various combinations of the anisotropies, exploring both positive and negative values. Our results reveal that the system exhibits standard second-order phase transitions for most parameter ranges, with no evidence of tricritical behavior. However, for certain positive values of the anisotropies, the model displays a first-order phase transition within the ordered phase, characterized by a jump from a higher-
spin ordered state to a lower-
spin ordered state. The critical temperatures are shown to be sensitive to the magnitude and sign of the anisotropy parameters. In particular, negative transverse anisotropies favor
magnetic order, raising the critical temperature, while positive anisotropies promote disorder, lowering the critical temperature. This study provides a comprehensive analysis of the phase diagram of the \( S = 5/2 \)
quantum Blume-Capel model and highlights the role of transverse fields in modifying the critical behavior.
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All authors Claudio M. Salgado, Karollaine C. Leite, Thiago M. Tunes, Marcelo F. Z. de Arruda, Jorge L. B. de Faria, Alberto S. de Arruda
Statistical Mechanics
Supercooling of liquids, as described by the Enskog-Vlasov kinetic equation
E. S. Benilov
A model combining Enskog's collision integral for dense fluids with a Vlasov-style description of the van der Waals force is applied to supercooling. First, the spinodal temperature $T_{s}$ is calculated, at which a
liquid becomes unstable to small perturbations and transitions to solid. In particular, it turns out that isochoric cooling allows one to reach a lower temperature than isobaric cooling. Second, the surface tension of a supercooled
liquid-vapor interface is shown to diverge at $T_{s}$. The singularity is caused by an oscillatory region emerging on the
liquid side of the interface as $T\rightarrow T_{s}$; it develops because the
liquid approaches instability, and the interface starts radiating (so far, evanescent) waves. At $T=T_{s}$, the waves cease to be evanescent and the oscillatory region extends to infinity – hence, the singularity of the surface tension. Since this effect has a clear physical interpretation, it should occur regardless of the model and approximations under which it was obtained. This and the other results of the paper are illustrated using argon and several other fluids.
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Strongly Correlated Electrons
Electronic Origin of Ferromagnetic Excitations in the Candidate Spin-Triplet Superconductor CeSb2
Xiaoxiao Wang, Xiaoyang Chen, Suppanut Sangphet et al. (+9 more)
The origin of quasi-one-dimensional (q1D)
ferromagnetic (FM) excitations in the candidate
spin-triplet
superconductor CeSb$_2$ has remained unclear. Here we report an electronic mechanism for emergent q1D magnetism in the quasi-two-dimensional
lattice of CeSb$_2$, revealed by angle-resolved photoemission spectroscopy (ARPES). High-resolution ARPES resolves no
spin-density-wave gap on the dispersive
Fermi pockets, disfavoring a nesting-driven mechanism for the q1D FM excitations. Instead, resonant ARPES reveals a pronounced selective enhancement of Ce 4$f$ spectral weight on the $C_2$-distributed
Fermi pockets aligned with the Ce ladder. This observation signifies band-selective Kondo coupling that generates strongly anisotropic
magnetic exchange interactions, which can naturally account for both the q1D
ferromagnetic excitations and the competing
magnetic orders. Our results identify a band-selective Kondo coupling mechanism for emergent low-dimensional magnetism in correlated $f$-electron systems.
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All authors Xiaoxiao Wang, Xiaoyang Chen, Suppanut Sangphet, Yifei Fang, Yilin Wang, Chihao Li, Minyinan Lei, Nan Guo, Yuanhe Song, Rui Peng, Haichao Xu, Donglai Feng
Strongly Correlated Electrons
Slave-rotor theory of correlated altermagnets on the Lieb lattice
Vanuildo S. de Carvalho, Hermann Freire and Rodrigo G. Pereira
We investigate the metal-
insulator transition driven by the onsite repulsive interaction $U$ in an altermagnetic Hubbard model defined on a Lieb
lattice. Using the slave-rotor approach at half-filling, we find that the system exhibits a cascade of interaction-driven phase transitions. As $U$ increases, the system evolves from a normal metal to an altermagnetic metal, then to an altermagnetic
insulator, and eventually to an altermagnetic Mott
insulator characterized by the complete suppression of the quasiparticle weight. These phases are supported by the calculation of the electronic spectral function, which features
spin-split bands in both the metallic and insulating regimes. However, the
spin splitting becomes substantially suppressed in the Mott-insulating phase. Our results suggest that the observation of
spin splitting in the spectral function of $d$-wave altermagnets with a Lieb-
lattice-like structure may be limited to the weak-to-moderate correlation regime.
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Statistical Mechanics · Cross-listed from cs.LG
Ridge Regression from Poisson Resetting: A Renewal Perspective on Spectral Regularization
Petar Jolakoski
We connect
stochastic resetting from non-
equilibrium statistical physics with ridge regularization in statistical learning. For linear gradient flow, resetting to the origin at rate $r$ produces stationary mean $(X^\top X+rI)^{-1}X^\top y$, exactly the ridge
estimator with penalty $\lambda=r$. This uses the known Laplace-transform relationship between ridge regression and exponential-time averaging of gradient flow, with the exponential time now interpreted as the stationary age associated with Poisson resetting. We then extend this identity to general renewal reset laws: the exponential reset time distribution is the unique renewal law whose stationary mean reproduces scalar ridge in every eigendirection as an exact filter identity for every positive
curvature, while non-exponential renewal laws generate alternative spectral filters. At the fluctuation level, we study a separate additive Ornstein-Uhlenbeck extension with constant
diffusion, interpreted as a stylized SGD approximation. In this setting, the equality holds only at the level of the mean, since the reset process has a nonzero stationary covariance from accumulated OU noise and reset-timing variance, whereas deterministic ridge is a fixed
estimator with the same center. Stylized experiments compare the deterministic renewal-induced filters directly and illustrate when filters induced by non-exponential reset-time laws can differ predictively from ridge. The results for the stationary mean and the induced spectral filters are established for continuous-time gradient flow with isotropic resetting on quadratic objectives; the covariance and risk formulas additionally assume additive noise with state-independent covariance.
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Mesoscale and Nanoscale Physics
Surface Originated Cross-Field Anomalous Transport in Magnetoelectric Multilayers
Jin Cao, Wei Du, Xue-Jin Zhang et al. (+3 more)
In material systems with slab geometry, the surface contribution to physical responses is commonly expected to diminish rapidly with increasing thickness, giving way to the bulk response. Here, we show that this conventional wisdom is violated in a class of gate-induced responses, including gate-induced orbital and
spin magnetization as well as cross-field anomalous thermoelectric transport. We develop a general framework for these effects, which naturally decomposes the total response into surface- and bulk-contributions treated on equal footing. Remarkably, the volume-averaged surface contribution remains finite in the thick-slab limit and exhibits the same thickness scaling as the bulk term. Furthermore, the surface response originates from band
geometric quantities distinct from those in the bulk, being constrained solely by surface
symmetries. As a result, it can dominate the overall response when the bulk contribution is
symmetry-forbidden. Taking MnBi$_2$Te$_4$ multilayers as an example, we predict a strong surface-dominated cross-field anomalous Nernst effect arising from surface Berry
curvature, which is readily accessible to experimental detection. These findings reveal a previously overlooked significance of surface response and open a new direction in the study of surface
quantum geometry.
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All authors Jin Cao, Wei Du, Xue-Jin Zhang, Cong Xiao, Qian Niu, Shengyuan A. Yang
Statistical Mechanics · Cross-listed from math.PR
Critical exponents for planar random-cluster model with cluster-weight $q=4$
Hong-Bin Chen, Hugo Duminil-Copin, Tiancheng He et al. (+4 more)
Using the Baxter-Kelland-Wu coupling and the convergence of the height function of the six-vertex model to the Gaussian Free Field, we extract critical exponents for the planar critical random-cluster model at $q=4$, and the planar four-state Potts model.
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All authors Hong-Bin Chen, Hugo Duminil-Copin, Tiancheng He, François Jacopin, Dmitry Krachun, Ioan Manolescu, Jiaming Xia
Materials Science
Hysteretic phononic band structures arising from martensitic phase transformations
R. Esquivel-Sirvent, B. Manzanares-Martínez and J. Manzanares-Martínez
Thermal tuning of phononic
crystals typically treats each constituent's elastic modulus as a single-valued function of temperature. Here we show that when one constituent undergoes a first-order martensitic transformation (NiTiCu), paired with a Parylene C spacer in a thin one-dimensional composite rod, the intrinsic thermal hysteresis of the transformation is transferred to the collective acoustic response, making it depend on thermal history. Transfer-
matrix calculations performed separately along the heating and cooling branches reveal that the same temperature within the transformation interval can correspond to two distinct Bloch band structures and two distinct transmission spectra. As temperature is cycled, stop-band edges trace closed loops in the temperature-frequency plane, producing hysteretic phononic band structures. At a fixed probe frequency, the rod can switch between transmitting and strongly attenuating states depending solely on whether the sample was last heated or cooled, with transmission contrasts exceeding 50 dB in a six-
cell structure, thereby realizing a form of acoustic
memory. The filling fraction of the active segment provides an independent
geometric control parameter that modifies the width of the hysteresis loops and the positions of gap closures. These predictions can be tested directly using immersion-ultrasonic measurements on NiTiCu/Parylene C composite rods.
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Materials Science
Magnetic precession induced spin accumulation in collinear antiferromagnets
Q. Xue and J. Zhou
Generating and characterizing uniform and staggered
spin polarization in antiferromagnets is one of the key challenges for
antiferromagnetic spintronic technology. Here, we perform perturbative theory, group-theoretical
symmetry analysis, low energy and ab initio simulations to propose that the
magnetic precession near the
equilibrium magnetic axis could generate finite uniform and staggered
spin polarization at the opposite
magnetic sublattices (referring to total
magnetic and Néel vector generation) in a single AFM
semiconductors. This response does not require the heterojunction setup and could eliminate the
lattice mismatch issues at the junction. Through scrutinizing all symmetrically-protected vanishing
magnetic moment groups and especially focusing on parity-time (PT ) invariant groups, we identify the
symmetry constraints that describe the staggered
spin accumulation responses, and disclose their fieldlike and dampinglike characters. This unravels a hidden
spin accumulation mode in AFM
semiconductors. Furthermore, we simulate such an effect using a perturbative approach and suggest that electric gate field and Floquet light-dressing can effectively manipulate these responses.
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Materials Science
Charting the thermodynamic stability of hybrid perovskite alloys with machine learning
Jarno Laakso, Armi Tiihonen and Patrick Rinke
Alloy-based perovskite
semiconductor materials offer tunable properties and improved stability, but their complexity has impeded accurate modeling, hindering development of
solar cell devices. We present a machine-learning (ML) accelerated atomistic modeling approach for the phase stability of (Cs/FA)Pb(Br/I)3 and (Cs/FA)Sn(Br/I)3 perovskites (where FA is formamidinium), that explicitly accounts for finite-temperature
entropy effects. To make such quaternary
alloy calculations tractable, we adopt a two-level strategy, combining 1) graph neural network interatomic potentials trained on density functional theory data for efficient structure relaxations with 2) direct energy predictions from unrelaxed structures to further accelerate the process. Our strategy enables computations of free energy landscapes across compositions and phases, capturing
alloy disorder and molecular orientations of FA. Our results reveal narrower regions of stable compositions for the Sn-based system compared to its Pb-based counterpart, limiting compositional engineering strategies for realizing devices that are robust in long term. High I contents result in maximum stability and no stabilization is observed near the center of the composition space. Our results guide the design of stable perovskite-based devices in experiments and demonstrate a workflow that is generalizable to other complex
alloy modeling tasks.
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Statistical Mechanics
Hidden Ising models from the generalized Yang-Baxter equation
Akash Sinha, Somnath Maity, Pramod Padmanabhan et al. (+1 more)
We introduce a one dimensional
spin $\frac{1}{2}$
Hamiltonian with multi-site interactions, but still local. The
algebra of its
Hamiltonian densities resembles that of the transverse field Ising model. Using this fact we show that its spectrum is free-fermionic but with a huge degeneracy for each level. The source of the degeneracy is a set of local conserved quantities that act like a classical background field for the
quantum system. The thermodynamics of this system is contrasted with the standard Ising model. At the gapless points in the energy spectrum, we show that this system can be derived from the
quantum inverse scattering method adapted to a multi-site generalization of the Yang-Baxter equation as introduced by E. Rowell and Z. Wang. The $R$-
matrix is constructed using generators of extraspecial 2-groups. This helps us extract all the conserved charges and lay the framework for a general mechanism to generate such multi-site interaction
spin systems that are transverse field Ising models under the hood. A remark on how to obtain P. Fendley's free-
fermion in disguise models in this formalism is also included.
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All authors Akash Sinha, Somnath Maity, Pramod Padmanabhan, Vladimir Korepin
Mesoscale and Nanoscale Physics
Thermodynamic and magnetocaloric properties of a triangular spin-1/2 cluster with Dzyaloshinskii-Moriya interaction
Jordana Torrico, Romulo A. Silva, S. M. de Souza et al. (+1 more)
We present a theoretical investigation of the
magnetic and thermodynamic properties of the triangular
spin-1/2 cluster with Dzyaloshinskii-Moriya (DM) interaction, described by a
spin-1/2 Heisenberg
Hamiltonian with antisymmetric exchange interactions. The energy spectrum and ground-state phase diagram reveal the presence of
ferromagnetic (FM), ferrimagnetic (FI), and frustrated (FR) phases, strongly influenced by the total
spin and the DM interaction. We analyze magnetization and susceptibility, showing that at low temperatures the system exhibits a characteristic 1/3 magnetization plateau, while thermal fluctuations suppress
magnetic order at higher temperatures. The
entropy and specific heat display residual
entropies due to ground-state degeneracies, Schottky-type anomalies at intermediate temperatures, and additional low-temperature features related to phase transitions. Particular
attention is given to the magnetocaloric effect (MCE), characterized by both direct and inverse regimes depending on the
magnetic field variation. We find that the DM interaction enhances the complexity of the MCE, leading to nontrivial
entropy variations as a function of the
magnetic field. These results provide insights into the role of frustration and anisotropy in tuning the MCE of properties triangular
spin clusters, with relevance to \mathrm{Cu}_{3}-based molecular magnets.
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All authors Jordana Torrico, Romulo A. Silva, S. M. de Souza, Onofre Rojas
Superconductivity
Stability Analysis of Superconductivity in $\textit{P6/mmm}$-LaSc$_2$H$_{24}$ and its Experimental Reproducibility from La-Sc Alloys
Dmitrii V. Semenok, Ivan A. Troyan, Zhongyan Wu et al. (+4 more)
In this work, we analyze the feasibility of room-temperature superconductivity in the lanthanum-scandium hydride $\textit{P6/mmm}$-LaSc$_2$H$_{24}$. We demonstrate that the electron-
phonon coupling calculations performed using the ${\sigma}$-broadening of the double ${\delta}$-function at the
Fermi surface lead to a very strong dependence of $\textit{T$_c$}({\sigma})$ on the arbitrary ${\sigma}$, whereas the tetrahedral method for the electron-
phonon interaction is free from this drawback and leads to $\textit{T$_c$}$ > 300 K at 300 GPa in agreement with previous predictions. By analyzing the stability of the metallic state of LaSc$_2$H$_{24}$ at 250-300 GPa, we show that this compound is at the edge of the stability region (${\xi}$ = 0.54), similar to $\textit{fcc}$ LaH$_{10}$ at 140-150 GPa. Seven experimental attempts to synthesize LaSc$_2$H$_{24}$ at 250-280 GPa starting from the (La,Sc$_2$)
alloy are unsuccessful and indicate the absence of even traces of superconductivity at 245-300 K in all the resulting La-Sc-H hydrides. The method for preparing the precursor by simultaneous deposition of La and Sc metals may be a key factor for the successful synthesis of LaSc$_2$H$_{24}$.
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All authors Dmitrii V. Semenok, Ivan A. Troyan, Zhongyan Wu, Di Zhou, Emil A. Yuzbashyan, Boris L. Altshuler, Viktor V. Struzhkin
Materials Science
Prototype-Guided Latent Alignment for Data-Efficient Fine-Tuning of Molecular Foundation Models
Rushikesh Pawar, Harshit Rawat, Ayush Kumar et al. (+1 more)
Machine learning interatomic potentials (MLIPs) have transformed materials discovery by leveraging graph neural networks (GNNs) to predict material properties with near density functional theory (DFT) accuracy. While large-scale pretrained foundation models offer transferable baseline representations, they frequently struggle to generalise to out-of-distribution (OOD) target systems – a common challenge in modelling complex or chemically diverse materials. Fine-tuning is the standard remedy, but the high cost of generating DFT-labelled configurations confines adaptation to data-scarce regimes, where over-parameterised GNNs amplify overfitting and degrade target-domain performance. To address this, we propose a prototype-based
alignment approach for data-efficient fine-tuning of MLIPs. Our method identifies local structural similarities between the source and target domains by grouping atoms with analogous chemical environments based on their latent representations. Each target-domain atom's energy contribution is aligned to its source-domain prototype, introducing an inductive bias that anchors fine-tuned representations to the pretrained structure, encouraging effective reuse of learned interactions and improving generalisation without restrictive assumptions on the target chemistry. We evaluate our method on the rMD17
benchmark using equivariant MACE and invariant SchNet across varying data budgets, and extend evaluation to the MACE-OFF foundation models on the SPICE
dataset. Our approach consistently improves predictive accuracy in the low-data regime, reducing energy MAE by up to 18% over standard fine-tuning baselines.
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All authors Rushikesh Pawar, Harshit Rawat, Ayush Kumar, Phani Motamarri
Soft Condensed Matter
Synergistic approach to probing the dynamics and mechanics of patchy soft matter
Md Mozakker H. Shojib, Asier C. Monasterio, Emanuele Locatelli et al. (+3 more)
Tailoring microscopic details to tune bulk rheology is a key paradigm in soft matter physics, yet the vast parameter space associated with constituent interactions precludes a fully systematic approach. To address this, we have designed a synergistic strategy to explore the parameter space that comprises simulations, experimental rheology, and machine learning. As a case study, we choose DNA-based self-assembled fluids whose viscoelastic response can be fine-tuned by manipulating the base sequencing of the constituent nucleic acid nanostars. We use coarse-grained simulations, benchmarked against experimental data, to obtain the rheology of the DNA fluids, which feeds forward to a framework of Gaussian Process Regression and active learning. The latter is then used to explore the rheological design space with high predictive precision. The pipeline is designed to be deployed iteratively for the rational design and accelerated discovery of generic soft matter suspensions.
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All authors Md Mozakker H. Shojib, Asier C. Monasterio, Emanuele Locatelli, Pascal Friederich, Christopher Ness, Iliya D. Stoev
Statistical Mechanics · Cross-listed from q-bio.PE
Lattice Brownian bees with cooperative reproduction: steady states, collapse, and spreading
Ohad Vilk and Baruch Meerson
We extend the “Brownian bees” model of Berestycki et al.\ (2021, 2022) to cooperative reproduction, $kA\to(k{+}1)A$, of a population of $N$ symmetric random walkers with removal, at each birth event, of the particle farthest from the origin. Working in the limit $N\to\infty$, we formulate a hydrodynamic free-boundary problem for this model. Using this formalism, we determine steady state population densities for all~$k$ and prove their linear stability for $k\le 2$ and instability for $k\ge 4$. In the marginal case $k=3$, there is a whole continuous family of steady states at a single critical ratio of the reproduction and
diffusion rates. Above criticality the population undergoes an asymptotically self-similar finite-time collapse to the origin. Below the criticality the population spreads diffusively, but the reproduction remains quantitatively relevant. For $k\ge 4$, the unstable steady state separates regimes of a finite-time collapse and diffusive spreading. Here the collapse dynamics is asymptotically self-similar, and the population density exhibits a scale separation requiring a matched-asymptotic description. Our analytical predictions are confirmed by numerical solutions of the hydrodynamic free-boundary problem and by Monte Carlo simulations of the original microscopic model.
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Statistical Mechanics
Universal thermokinetic decomposition of short-time information fluctuations
Giorgio Nicoletti and Daniel M. Busiello
Biological, artificial, and physical systems dissipate energy to accurately transmit information. While tools of information theory have been used to characterize information-processing capabilities, how reliably this information is acquired along individual trajectories, and which aspects require a thermodynamic cost, is an open question. In this work, we focus on the
stochastic predictability of an arbitrary Langevin dynamics, defined as the pointwise mutual information between the current and future states of a system. We show that the fluctuations of predictability obey a universal thermokinetic decomposition at short times, which reveals that information fluctuations are suppressed by energy dissipation and become stronger with increased dynamical activity. Remarkably, we find that the average predictability, i.e., the short-time mutual information, does not carry any dependence on the underlying thermodynamic and kinetic features. Thus, the role of dissipation at short times is not to enhance information, but to reduce its fluctuations. Such dissipative control is effective only when instantiated by nonlinear operations. Moreover, energy consumption governs short- and long-time precision in
stochastic oscillators through structurally different mechanisms that can be independently tuned. Our decomposition offers a fundamental thermodynamic basis for understanding the reliability of information transmission in nonequilibrium systems, the constraints on precision in biological systems, and the design of energy-limited control strategies.
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Statistical Mechanics
Entropy of Liquids and Glasses from Recurring Structural Patterns
Nina Javerzat, Gerhard Jung, Jorge Kurchan et al. (+1 more)
We compute the low-temperature configurational
entropy of a two-dimensional supercooled
liquid. Our method, based on a higher-dimensional version of the Grassberger–Procaccia
algorithm, can be implemented in a manner that is entirely agnostic with respect to both the dynamics and the theoretical framework, as any genuine notion of order should be. In this construction,
entropy is obtained as the decay rate of recurrent structural patterns with increasing patch size, directly linking
entropy reduction to the growing persistence of amorphous order. Because the method requires only particle positions, without any knowledge of the interaction potential or even of the particle sizes, it can be applied directly to both
equilibrium and nonequilibrium aging configurations. The resulting configurational
entropy, together with the higher-order Rényi complexities, agree quantitatively with values obtained from conventional definitions. Remarkably, the
entropies measured during aging coincide with their
equilibrium counterparts when compared at the same inherent-structure energy.
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All authors Nina Javerzat, Gerhard Jung, Jorge Kurchan, Misaki Ozawa