Quantum Gases
Spinor condensate persistent currents in an atomtronic Josephson necklace
Sayan Chatterjee, Nalinikanta Pradhan, Rina Kanamoto et al. (+2 more)
The investigation of superflow in multi-junction Josephson
circuits is currently a leading frontier of physics research, probing the fundamental manifestations of macroscopic phase coherence and enabling applications to
quantum simulation, metrology and computing. In this work, we extensively investigate the stability and dynamics of persistent currents of a spinor atomic Bose-Einstein condensate on a ring with multiple Josephson junctions. Specifically, we examine the effects of positive and negative interspecies interactions, co- and counter-rotation, population and Manakov asymmetry, as well as Rabi coupling on the persistent currents carried by the two components. Our analysis reveals that the presence of a second species offers multiple mechanisms for unprecedented manipulation of supercurrents on the ring, including phase-slip engineering, stability control, current-inversion switching and supercurrent pumping. Our study provides a roadmap for the engineering of persistent currents in binary ring condensates in necklace potentials, with significant implications for atomtronics, matter-wave interferometry and sensing using atomic Bose gases.
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All authors Sayan Chatterjee, Nalinikanta Pradhan, Rina Kanamoto, M. Bhattacharya, Pankaj Kumar Mishra
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Dissipation-induced Sachdev-Ye-Kitaev physics in many-body cavity quantum electrodynamics
Pietro Pacchioni, Filippo Ferrari, Vincenzo Savona et al. (+1 more)
We show that cavity
quantum electrodynamics (QED) devices can realize dissipative Sachdev-Ye-Kitaev (SYK) universality, a paradigmatic setting for
quantum chaos in open many-body systems. Ultracold
fermions with disordered, all-to-all cavity-mediated interactions provide two complementary routes: atomic spontaneous emission in a single-mode cavity and
photon leakage from a multimode cavity. Strikingly, both converge to the same non-Hermitian random-
matrix universality despite originating from integrable and chaotic closed-system limits, respectively. In the single-mode cavity, dissipation creates
quantum chaos from an integrable
Hamiltonian. We trace this convergence to a tunable growth in dissipative rank, controlled, respectively, by the Lamb-Dicke parameter and the cavity-mode spacing. The integrability-to-chaos crossover is accompanied by a dynamical crossover from long-lived prethermal
memory to rapid thermalization, visible in single-atom-resolved densities.
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All authors Pietro Pacchioni, Filippo Ferrari, Vincenzo Savona, Matteo Seclì
Mesoscale and Nanoscale Physics
Quaternionic Hermitian Band Geometry in Four Dimensions: Realization on $S^4$ and Obstruction on $T^4$
Dongju Hwang, Minjae Yu and Gil Young Cho
We establish a realization-obstruction dichotomy for quaternionic Hermitian band geometry in four-dimensional parameter spaces: the minimal-charge lowest Landau level on $S^{4}$ provides a global realization, whereas an everywhere nondegenerate saturated realization induced by a single occupied quaternionic band is obstructed on $T^{4}$. An antiunitary
symmetry $\mathcal{J}$ satisfying $\mathcal{J}^{2}=-1$ makes the occupied doublet a quaternionic band. Within this setting, we formulate the quaternionic Wirtinger inequality as a band-
geometric bound involving the
quantum metric and the second Chern density. At every nondegenerate saturation point, the canonical geometry of the quaternionic projective space pulls back to a compatible quaternionic structure on the parameter space; if these conditions hold everywhere, the parameter space acquires quaternionic Hermitian band geometry. On $S^{4}$, we express the minimal-charge states as quaternionic Perelomov coherent states and establish everywhere nondegenerate saturation, thereby realizing quaternionic Hermitian band geometry. On $T^{4}$, by contrast, a minimal four-band system saturates the inequality everywhere, but
topology forces the
quantum metric to become degenerate somewhere, obstructing a globally induced quaternionic structure. An explicit
lattice Dirac
Hamiltonian exhibits this obstruction. Adding unoccupied bands cannot remove this obstruction when the inequality is saturated everywhere, since the image of any nondegenerate saturated projector remains confined to a fixed $\mathbb{H}P^{1}$. These results provide a
symmetry-aware framework for non-Abelian band geometry and show how parameter-space
topology constrains the global realization of quaternionic Hermitian band geometry.
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Statistical Mechanics
Non-Abelian Spin Counting of Ordered Stochastic Trajectories: Reentrant Finite-Time Chern Numbers
Yangyang Du
Conventional full counting statistics assigns commuting phases to integrated
stochastic currents and therefore resolves net transport but not, in general, the temporal ordering of events associated with different cycles. We introduce a non-Abelian counting construction in which crossings of two fundamental cycles rotate an auxiliary
spin about different axes. The resulting ordered trajectory statistic has an exact finite-dimensional
evolution equation for its first moment. The two rotation angles form a counting
torus, and whenever the mean
spin is nonzero its normalized direction defines a map $\mathbb T^2\to\mathbb S^2$, equivalently a complex eigenline bundle with a Chern number. Our main analytical result is a Chern–parity correspondence. Reflection
symmetry equips this eigenline with a real structure and expresses $C_T\bmod2$ through first Stiefel–Whitney classes on the circles fixed by reflection. When the transverse polarization has no additional zeros along the reflection-fixed circles, these classes reduce to ordinary current-parity statistics at the four high-
symmetry counting points. For a five-state nonequilibrium figure-eight network, varying only the observation time produces four polarization-gap closings and the reentrant sequence $C_T=0\to-1\to0\to-1\to0$. Every transition occurs at $(\pi,\pi)$ and coincides with a sign reversal of $\mathbb E[(-1)^{Q_1+Q_2}]$, while the full integer Chern number is obtained independently from the two-dimensional
spin texture. Finite observation time can therefore organize a fixed
stochastic process into distinct topological sectors of its ordered path ensemble.
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Statistical Mechanics
Run-and-tumble particles with preferred reorientation
Callum Britton, Ziluo Zhang, Seongjun Han et al. (+1 more)
Run-and-tumble particles (RTPs) are canonically modeled with uniform reorientation probabilities, an assumption that breaks down for many biological microswimmers. In this work, we investigate the dynamics of RTPs with arbitrary non-uniform tumble distributions. By deriving an exact Doi-Peliti field theory, we explicitly calculate a wide array of spatial and orientational observables. Notably, we demonstrate that the spatial dynamics exhibit an effective persistence and chirality governed entirely by the first
Fourier modes of the tumble distribution, establishing a formal mapping to the dynamics of
chiral active Brownian particles. Furthermore, our field-theoretic framework provides a systematic method to compute spatial moments to arbitrary order, allowing for the complete characterization and identification of complex tumbling dynamics. We illustrate the framework with wrapped Gaussian and bimodal Gaussian distributions, demonstrating explicit control over persistence and chirality. We further extend the field theory to $d$ dimensions, recovering the mean squared displacement in terms of a single effective tumble rate. Our results establish a direct link between the shape of the tumble distribution and the emergent dynamics, and provide a foundation for the study of interacting RTPs with non-uniform reorientation.
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All authors Callum Britton, Ziluo Zhang, Seongjun Han, Thibault Bertrand
Materials Science
Large Jahn-Teller shifts and splittings observed in halide perovskite CsPbBr3
Maryam Sajedi, Maxim Krivenkov, Dmitry Marchenko et al. (+7 more)
Despite the fundamental role of Jahn-Teller effects of first and second order in shaping structural and electronic properties, there is hardly any observation in angle-resolved photoemission of solids. In
oxide and halide perovskites, band structure replicas have occasionally been reported as fingerprints of Jahn-Teller effects, but no accompanying energy shifts or splittings that would allow a conclusion about their origin. In CsPbBr3, we uncover both key signatures: Upon cooling, orthorhombic replica bands emerge which had eluded earlier studies. This includes an extra valence band maximum at {\Gamma} which can even be distinguished at room temperature. Most importantly, band narrowing along {\Gamma}-M, a splitting at {\Gamma}, and the lifting of degeneracy between nonequivalent M points, all of several 100 meV, become apparent. Temperature-dependent x-ray diffraction, used as input for band structure calculations, links these effects directly to tilts and rotations of the PbBr6 octahedra. Our results uncover a strong electron-
lattice interaction which is at the heart of so-far unresolved questions concerning polaronic transport, dynamic disorder, and
exciton trapping in halide perovskites.
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All authors Maryam Sajedi, Maxim Krivenkov, Dmitry Marchenko, Saleem Ayaz Khan, Andrei Varykhalov, Jaime Sánchez-Barriga, Daniel M. Többens, Thomas Unold, Ján Minár, Oliver Rader
Strongly Correlated Electrons
Momentum-resolved EELS study of collective charge excitations in 1$T$-TaS$_2$
Farzaneh Hoveyda-Marashi, Xuefei Guo, Caitlin Kengle et al. (+5 more)
We use momentum-resolved electron energy-loss spectroscopy (M-EELS) to study the low-energy charge excitations of 1$T$-TaS$_2$ across the nearly commensurate-to-commensurate charge-density-wave (CDW) transition. Single-
crystal x-ray diffraction and elastic M-EELS measurements confirm the expected rotation of the CDW wave vector upon entering the commensurate phase. In the nearly commensurate phase, the low-energy M-EELS spectra reveal an acoustic
phonon branch and two optical
phonon features whose energies and dispersions are broadly consistent with previous calculations and inelastic x-ray measurements. Across the transition, the optical
phonon energies remain nearly unchanged, while their spectral intensity develops a pronounced temperature dependence near the CDW ordering wave vector. At higher energies, the finite-momentum charge response undergoes a substantial redistribution of spectral weight below the transition, consistent with the opening of an energy gap. These results demonstrate that M-EELS provides simultaneous access to
lattice dynamics and finite-momentum valence band charge excitations in 1$T$-TaS$_2$, revealing their
evolution across the commensurate CDW transition.
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All authors Farzaneh Hoveyda-Marashi, Xuefei Guo, Caitlin Kengle, Camille Bernal-Choban, Yue Su, Jin Chen, Dipanjan Chaudhuri, Peter Abbamonte
Soft Condensed Matter
Approaching the theoretical limit of wicking on textured surfaces
Zhaoyang Lv, Chen Ma, Li-Chen Huang et al. (+1 more)
Wicking in a capillary tube could happen as long as the
liquid contact angle is smaller than 90 degrees, making it possible for weak hydrophilic
liquids to spontaneously invade the tube. For textured surfaces, energy minimization argument predicts the same. However, wicking of weak hydrophilic
liquids on textured surfaces has not been possible due to energy barriers induced by the textures. We demonstrate how these barriers could be avoided by adjusting the shape and arrangement of the pillars, thus the wettability required for wicking reaches the theoretical limit. An unprecedented wicking contact angle of 82 degrees is reported. More surprisingly, wicking coefficients of such surfaces can be larger than that of rectangular grooves at the same porosity. These findings may significantly advance biomedical and thermal management technologies.
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All authors Zhaoyang Lv, Chen Ma, Li-Chen Huang, Yanshen Li
Materials Science
Emergent Noncollinearity and Near-Degenerate Magnetic Superlattices in AT6X6 Kagome Metals
Weiyi Xia, Wei-Shen Tee, Peter Minch et al. (+3 more)
Ferromagnetic AT6X6 Kagome compounds are a popular class of systems in which
quantum magnetism with topological features has been observed. These systems allow easy chemical substitution, creating an opportunity to fine-tune their properties. In this paper, we present electronic-structure and
magnetic ground-state studies of several AT6X6 compounds with relatively low
magnetic-ground-state stability. We find unusual
magnetic orderings, including complex
spin-spiral states and the formation of
magnetic long-range superstructures. While LiFe6Ga6 and TiMn6Ge6 retain collinear AFM ground states with low-energy FM/AFM layer sequences, competing
spin-spiral and long-period
antiferromagnetic structures in MgFe6Ga6 and a double-
spin-spiral ground state in TiFe6Ga6 were determined. Magnetism in all these systems appears local, with adiabatic energy profiles suggesting non-Heisenberg long-range interactions, including a strong biquadratic term. In TiMn6Ge6, we found the conditions for
magnetic tunneling. Our results show that, in addition to traditional
magnetic topological features in such FM Kagome systems, near-degenerate
magnetic superstructures suitable for spintronic switching applications can form naturally. Overall, these systems represent a potentially rich playground for
neutron diffraction and spintronics experimental studies.
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All authors Weiyi Xia, Wei-Shen Tee, Peter Minch, Feng Zhang, Cai-Zhuang Wang, Vladimir Antropov
Superconductivity
Competing Extended-$s$- and $d$-Wave Pairing from Distinct Spin-Fluctuation Channels in Stoichiometric $\mathrm{FeTe}$
Yichen Hua, Wen-lin Yang, Jian-Jian Miao et al. (+2 more)
The recent observation of superconductivity in stoichiometric $\mathrm{FeTe}$ raises the question of how pairing develops in this tetragonal 11-type chalcogenide once interstitial Fe is removed. We construct an experimentally constrained five-orbital tight-binding model from first-principles calculations and treat electronic correlations and pairing within the fluctuation-exchange approximation. The linearized Eliashberg equation yields competing extended-$s$- and $d_{x^2-y^2}$-wave
spin-singlet pairing instabilities. Near stoichiometric filling,
spin fluctuations near $(\pi,0)$ and $(0,\pi)$ in the unfolded one-Fe Brillouin zone connect the $\Gamma/M$ hole pockets with the $X/Y$ electron pockets and favor an extended-$s$ gap that changes sign between the hole and electron sheets. Upon electron doping, depletion of the hole pockets shifts the dominant scattering toward the $X$–$Y$ channel near $(\pi,\pi)$, making the $d_{x^2-y^2}$-wave state the leading instability, with nodal lines that avoid most of the
Fermi surface. The relative strengths of the two pairing channels vary with filling and interaction strength as the dominant
spin-fluctuation channel changes. Under matched interaction strength, temperature, and filling, the extended-$s$
eigenvalue is larger in $\mathrm{FeTe}$ than in $\mathrm{FeSe}$ throughout the range considered, while the $d_{x^2-y^2}$-wave
eigenvalue is also generally larger, particularly under electron doping. These results give concrete gap structures against which spectroscopic measurements of stoichiometric $\mathrm{FeTe}$ can be compared.
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All authors Yichen Hua, Wen-lin Yang, Jian-Jian Miao, Hu Xu, Changming Yue
Statistical Mechanics
Cramer-Rao Inequality Generalizes the Equilibrium Energy Fluctuation-Response Relation to Nonequilibrium Steady States
Shaofan Liu, Raphael Chetrite and Andre C. Barato
Equilibrium steady states are fully characterized by the Boltzmann distribution, which depends only on the energy and the temperature. In contrast, nonequilibrium steady states, which describe a wide range of physical and biological phenomena, are generically much more complex, and their stationary distributions can depend on a zoo of kinetic parameters. A central challenge of nonequilibrium statistical mechanics is the identification of universal relations that hold for nonequilibrium steady states despite this complexity. We show here that a form of the Cramer-Rao inequality applies to arbitrary nonequilibrium steady-state distributions and contains no explicit dependence on kinetic parameters. A main original feature in our observation is that this inequality becomes a well-known fluctuation-response relation in
equilibrium. The inequality involves three well-defined quantities: the fluctuations of the energy, the response given by the derivative of the average energy with respect to the inverse temperature, and the Fisher information with respect to the inverse temperature. We illustrate this inequality using three representative models: an active particle in a harmonic potential, a simple scheme for kinetic proofreading, and a one-dimensional model for heat conduction between two baths.
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Soft Condensed Matter
One micron length scale controls kinetic stability of low energy glasses
Kenneth L. Kearns, M. D. Ediger, Heiko Huth et al. (+1 more)
AC nanocalorimetry was used to measure the reversing heat capacity Cp of low energy indomethacin glasses as they isothermally transform into the supercooled
liquid. As the film thickness increases from 75 to 600 nm, the transformation time increases by more than an order of magnitude, consistent with a surface-initiated transformation mechanism. Eventually, the transformation time becomes constant for films between 1.4 and 30 microns indicating a distinct bulk transformation pathway. The observation of size-dependent transformation kinetics for glass samples approaching 1 micron is unprecedented. We interpret the crossover in thickness dependence at 1 micron to signify the average distance between transformation initiation sites in the bulk low energy glass.
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All authors Kenneth L. Kearns, M. D. Ediger, Heiko Huth, Christoph Schick
Soft Condensed Matter
Highly Stable Glasses of cis-Decalin and cis/trans-Decalin Mixtures
Katherine R. Whitaker, Daniel J. Scifo, M. D. Ediger et al. (+2 more)
In situ AC nanocalorimetry was used to measure the reversing heat capacity of vapor-deposited glasses of decahydronaphthalene (decalin). Glasses with low heat capacity and high kinetic stability, as compared to the corresponding
liquid-cooled glass, were prepared from cis-decalin and from several cis/trans-decalin mixtures. This is the first report of highly stable glass formation for molecular mixtures. The 50/50 cis/trans-decalin mixture is the highest fragility material reported to produce an ultrastable glass. The 50/50 mixture exhibited high kinetic stability, with an ~500 nm film deposited at 116 K (0.86 Tg,) displaying a transformation time equivalent to 104.4 times the structural relaxation time of the supercooled
liquid at the annealing temperature. Cis-decalin and the decalin mixture formed stable glasses that had heat capacities as much as 4.5% lower than the
liquid-cooled glass.
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All authors Katherine R. Whitaker, Daniel J. Scifo, M. D. Ediger, Mathias Ahrenberg, Christoph Schick
Strongly Correlated Electrons
Interaction-mediated Co-existence of Altermagnetism and Topology
Jasmin Bedow, Nitin Kaushal and Marcel Franz
We study an extended Hubbard model on Lieb
lattice at electron filling 2 and 4, and demonstrate that the interactions lead to the simultaneous emergence of altermagnetic order and a topological gap. Using unrestricted Hartree-Fock theory, we evaluate both the altermagnetic and topological order parameters and show that they co-exist with an associated
quantum spin Hall effect in a large region of the phase diagram, which we further support using exact diagonalization. Moreover, we demonstrate that inversion-
symmetry breaking terms can also mediate second-order topological phases with associated corner modes.
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Materials Science
Defect-Mediated Nucleation and Dynamics across the Phase Transition in the Excitonic Insulator Candidate Ta2NiSe5
Guilherme Rodrigues-Fontenele, Gabriel Fontenele, Ângelo Malachias et al. (+1 more)
Ta2NiSe5 is a quasi-one-dimensional material that exhibits a structural and electronic phase transition from a low-temperature monoclinic (
semiconductor) to a high-temperature orthorhombic (semimetal) phase at approximately TC = 326 K. Here, we used variable-temperature scanning tunneling microscopy and spectroscopy to resolve the phase transition spatially, identifying the distinct spectroscopic signatures of the monoclinic and orthorhombic phases in pristine regions and near isolated point-defects and step edges. Although the phase transition of Ta2NiSe5 is generally regarded as second-order, it has previously been described as exhibiting martensitic-like characteristics. This implies that the transformation may proceed via spatial phase coexistence and domain boundaries rather than through a continuous
evolution. Our surface-sensitive measurements confirm this scenario, retrieving the coexistence and
evolution of monoclinic and orthorhombic domains in real space. Upon heating through TC, we find that the two phases coexist as spatially segregated regions over extended timescales, separated by well-defined boundaries that evolve via localized nucleation and growth, rather than a spatially uniform transformation. In pristine regions, the orthorhombic phase nucleates anisotropically, perpendicular to the Ta-Ni-Ta chains, whereas point-defects and step edges act as local nucleation centers that promote the transition and suppress this intrinsic anisotropy. These results provide direct real-space visualization of how surface-specific structural and electronic variations, together with local disorder, modify the martensitic-like phase transition in Ta2NiSe5.
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All authors Guilherme Rodrigues-Fontenele, Gabriel Fontenele, Ângelo Malachias, Rogério Magalhães-Paniago
Soft Condensed Matter
Comparison of mechanical and molecular measures of mobility during constant strain rate deformation of a PMMA glass
Benjamin Bending and M.D. Ediger
We performed constant strain rate deformation and stress relaxation on a poly(methyl methacrylate) glass at Tg - 19 K, utilizing three strain rates and initiating the stress relaxation over a large range of strain values. Following previous workers, we interpret the initial rate of decay of the stress during the relaxation experiment as a purely mechanical measure of mobility for the system. In our experiments, the mechanical mobility obtained in this manner changes by less than a factor of 3 prior to yield. During these mechanical experiments, we also performed an optical measurement of segmental mobility based upon the reorientation of a molecular probe; we observe that the probe mobility increases up to a factor of 100 prior to yield. In the post-yield regime, in contrast, the mobilities determined mechanically and by probe reorientation are quite similar and show a similar dependence upon the strain rate. Dynamic heterogeneity is found to initially decrease during constant strain rate deformation and then remain constant in the post-yield regime. These combined observations of mechanical mobility, probe mobility, and dynamic heterogeneity present a challenge for theoretical modeling of
polymer glass deformation.
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Materials Science
Resistive Switching and Neuromorphic Computing in Metal/Nb:SrTiO$_3$: Mechanisms, Interface Physics, and Charge Transport
Christopher Broyles, Elizabeth Krenkel, Frank Barrows et al. (+2 more)
Resistive switching (RS) in Nb-doped SrTiO$_3$ (Nb:STO) based memristive devices has attracted sustained interest in information processing and novel computing because of its forming-free operation, large on/off ratio, and gradual conductance modulation. Metal/Nb:STO Schottky junctions have emerged as a prototypical system for understanding RS mechanisms. Despite more than two decades of research, the physical origin of RS remains controversial, with proposed mechanisms including charge trapping and detrapping, oxygen vacancy migration, tunneling, interfacial redox reactions, and conductive filament formation. In this review, we examine these seemingly competing mechanisms and show that many experimental observations can be understood within a unified framework centered on the formation and
evolution of an extrinsic interfacial layer at the metal/Nb:STO interface. We discuss how interface quality and defect-mediated processes, including
proton incorporation, oxygen vacancy dynamics, and tunneling, govern Schottky barrier modulation and RS behavior. We further summarize how fabrication conditions, measurement protocols, and aging influence the interface formation and switching characteristics. This review establishes an integrated picture of M/Nb:STO heterojunctions and provides design principles for reliable
oxide memristive devices through interface and defect engineering in M/Nb:STO and M/
oxide/Nb:STO systems.
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All authors Christopher Broyles, Elizabeth Krenkel, Frank Barrows, Sundar Kunwar, Aiping Chen
Disordered Systems and Neural Networks · Cross-listed from nlin.AO
Inertial synchronization of networked oscillators in arbitrary dimensions
Kirill Kovalenko, Bruce X. Dai, Fanshu Fang et al. (+6 more)
The Kuramoto model provides a paradigmatic framework for studying synchronization of interacting oscillators, and has been generalized to arbitrary dimensions to describe swarms, flocks and multi-dimensional opinion dynamics. Yet, existing formulations neglect inertia, a key mechanism known to enhance information propagation and collective responsiveness. Here, we introduce and analyze an inertial Kuramoto model in arbitrary dimensions. We show that inertia fundamentally alters the nature of the synchronization transition, inducing a crossover from continuous to discontinuous behavior, with the onset of hysteresis depending explicitly on both inertia and dimensionality parity. Our analytical theory is supported by extensive numerical simulations. These results establish inertia as a crucial ingredient of high-dimensional collective dynamics and reveal a novel universal structure in synchronization phenomena.
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All authors Kirill Kovalenko, Bruce X. Dai, Fanshu Fang, Zerong Guo, Haoran Liu, Federico Botta, Charo I. del Genio, Stefano Boccaletti, Simona Olmi
Soft Condensed Matter · Cross-listed from physics.chem-ph
Environmental Control Extends Beyond Quantum Dephasing in Exciton Energy Transfer
Junhua Zhou, Tianrui Chen, Dehao Yuan et al. (+8 more)
Excitation-energy transfer underpins the conversion of light into usable energy in photosynthetic organisms and serves as a paradigm for evolutionary optimized transport in open
quantum systems. Although this process is often described as incoherent thermally assisted hopping, such descriptions become inadequate when electronic coupling, vibronic interactions and environmental fluctuations occur on comparable energy scales. Determining how the environment controls transport therefore remains a fundamental challenge. Here, we use temperature-dependent 2DES to investigate energy transfer in the photosynthetic
antenna protein allophycocyanin over the range 10 - 296 K. The dominant $\beta \rightarrow \alpha$ transfer step exhibits a pronounced non-monotonic temperature dependence: the transfer time decreases from 400 fs at 10 K to 200 fs near 30- 40 K before increasing again to 400 fs at 296 K. In contrast, the homogeneous optical dephasing time decreases monotonically across the same temperature range. To interpret these observations, we model APC as a vibronically coupled excitonic dimer interacting with a structured environment and solve the dynamics using hierarchical equations of motion. Conventional fixed-bath models, including Drude-Lorentz and explicit intermolecular-mode spectral densities, fail to reproduce the observed turnover. Quantitative agreement is obtained only when the low-frequency sector of the environmental spectral density is allowed to anharmonically evolve strongly with temperature, while the high-frequency bath remains essentially unchanged. More broadly, these findings demonstrate that transport efficiency is controlled not simply by the magnitude of environmental fluctuations, but by the distribution of environmental spectral weight across frequency space, providing new experimental constraints on theories of molecular transport in complex
quantum environments.
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All authors Junhua Zhou, Tianrui Chen, Dehao Yuan, Enhu He, Vandana Tiwari, Maxim Gelin, Francoise Remacle, R. J. Dwayne Miller, Fulu Zheng, Ajay Jha, Hong-Guang Duan
Materials Science
Mapping metallic d-wave altermagnetism across the TiNiSi structural family
Zhen Zhang, Subhadip Pradhan, Kirill D. Belashchenko et al. (+1 more)
The prospect of using altermagnets as switchable sources of perpendicularly polarized
spin currents has intensified the search for candidate materials, yet metallic d-wave systems with sizable
spin-splitter responses remain scarce. Here, we identify an empirical
magnetic motif that supports metallic d-wave altermagnetism in the TiNiSi structural family: ferromagnetically ordered zigzag chains with
antiferromagnetic interchain coupling in a relatively low-
symmetry crystal environment. The TiNiSi structure type combines this motif with broad chemical flexibility and competing
magnetic ground states. By combining first-principles screening of thermodynamic stability and
magnetic ground states across 280 ternary systems, we identify 16 metallic d-wave altermagnets. This set recovers four experimentally known members—WFeB, NbMnP, TaMnP, and NbMnAs—and yields 12 new predictions, of which ScMnP, TaMnAs, ScMnAs, MoMnAs, MoMnSi, and WMnSi are the most promising. Noncollinear calculations indicate that the collinear altermagnetic configuration is the ground state across them. Each of the six leading new candidates has a nonzero
spin-splitter angle and a finite anomalous
Hall conductivity. Notably, ScMnP and TaMnAs exhibit strong
spin-splitter responses despite modest altermagnetic band splitting. These results establish TiNiSi-type metallic d-wave altermagnets as a chemically versatile platform for efficient charge-to-
spin conversion and provide an empirical
magnetic-motif-guided route to identifying further candidates.
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All authors Zhen Zhang, Subhadip Pradhan, Kirill D. Belashchenko, Vladimir Antropov
Materials Science
The principle of detailed balance between electrons and phonons in presence of excitonic effects
Alberto Guandalini, Giovanni Caldarelli, Francesco Mauri et al. (+1 more)
Based on a many-body formulation, we derive an electron-
phonon coupling including excitonic effects that preserves thermodynamic detailed balance between electronic and phononic scattering processes. We start from the microscopic electron-
nucleus Hamiltonian, expand around the Born-Oppenheimer
equilibrium geometry, and construct an effective action for the electronic and phononic propagators. From the same effective action, we derive both electronic and phononic self-energies in terms of a nonlocal vertex $\mathcal G^{\textrm{s}}$ including excitonic effects, which generalizes the usual local interaction vertex $g^{\textrm{s}}$. When electrons and
phonons are well-defined quasiparticles in the screened-exchange approximation and $\mathcal G^{\textrm{s}}$ is taken in its static limit, both self-energies reduce to
Fermi-golden-rule expressions containing the same $\mathcal G^{\textrm{s}}$, thereby ensuring detailed balance. As an application, we compute electronic and phononic linewidths in
graphene and illustrate this common-vertex construction. We analyze the competition between the reduced scattering phase space induced by the screened-exchange band structure and the enhancement of the electron-
phonon vertex due to excitonic effects, finding that the vertex enhancement can compensate for and overcome the phase-space reduction in both electronic and phononic linewidths.
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All authors Alberto Guandalini, Giovanni Caldarelli, Francesco Mauri, Francesco Macheda
Statistical Mechanics
Free-Energy Differences from Nonequilibrium Fluctuations in High Dissipation
Sreekanth K Manikandan and Giovanni Volpe
Equilibrium free-energy differences can be measured from nonequilibrium work fluctuations using fluctuation
theorems, such as the Jarzynski equality and the Crooks fluctuation
theorem. However, these approaches become statistically inefficient in high-dissipation regimes because their convergence requires trajectories with negative
entropy production, events that occur exponentially rarely. Here, we demonstrate that repeated measurements of trajectory fluctuations are sufficient to determine
entropy production without relying on such rare events, or to determine a lower bound on it when only partial measurements are available. This information then yields exact estimates of free-energy differences, or rigorous bounds. We validate this approach, named EquiNET, with numerical simulations, including one of biomolecular folding and unfolding, showing that it recovers accurate free-energy estimates even in regimes where conventional approaches fail.
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Materials Science
FUCrIMODo: structure recovery from atomistic descriptors via multi-stage genetic algorithms
Louis Boehm, Martin Kuban and Claudia Draxl
Data-driven approaches to materials discovery rely on numerical representations of atomic structures as input for machine learning models. Inverting these descriptors - recovering atomic structures from their representations - is essential for most generative material design pipelines, yet it remains challenging, particularly for periodic systems. Existing inversion methods are either tailored to specific invertible descriptors or require candidate structures with similar atomic arrangements and compositions, limiting the exploration of novel regions in chemical and configurational space. Here, we propose a generalizable, similarity-driven sampling approach, powered by a novel stage-wise optimization strategy, to recover atom types, atomic positions, and unit
cell shapes directly from a descriptor. Our approach requires only descriptor features and parameters as input without any prior structural knowledge. The capability of our method is demonstrated by the averaged Smooth Overlap of Atomic Positions (SOAP) descriptor.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Quantum-Geometric Length Scale for Long-distance Squeezing in Bosonic Bogoliubov Systems
Sonu Verma, Sangmo Cheon, Myung-Joong Hwang et al. (+1 more)
Multimode squeezing is a key resource for continuous-variable
quantum technologies, but its spatial range in bosonic
lattices is usually tied to dispersive propagation. Here we show that parametric pairing can create an exactly flat Bogoliubov band spanned by compact Bogoliubov generators, while producing phase-sensitive anomalous correlations and sub-
vacuum collective-mode squeezing that extend far beyond their finite support. Each compact generator mixes annihilation and creation operators, thereby encoding the Bogoliubov squeezing structure, and neighboring translated generators can have nonzero commutator overlap. Enforcing canonical bosonic commutation relations therefore requires spatially extended linear combinations of these translated compact generators, which define the canonical Bogoliubov modes. The squeezing transformation of these modes varies with momentum and is quantified by the squeezing-sector
symplectic quantum metric. A complex-momentum singularity of the analytically continued canonical Bogoliubov modes sets both the anomalous-correlation decay length and the momentum-space width of this metric, defining an intrinsic
quantum-
geometric length scale. This singularity can be tuned continuously while preserving exact flatness, thereby controlling the spatial range of correlations and squeezing. Away from exact flatness, long-distance correlations persist through multiple decay channels, while modes localized by defects and dimerized boundaries provide complementary probes of the underlying
quantum geometry. In the weak-damping limit, the same
quantum-
geometric length scale can be extracted from frequency-filtered two-port correlations. Our results establish the
quantum geometry of canonical Bogoliubov modes as a mechanism for spatially extended
quantum resources arising from compact Bogoliubov generators.
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All authors Sonu Verma, Sangmo Cheon, Myung-Joong Hwang, Moon Jip Park
Strongly Correlated Electrons
A DQMC study of the spectral and conductive properties of the two-dimensional Holstein model
J. Neuhaus, B. Cohen-Stead, N. Mannella et al. (+1 more)
We study the dynamical properties of the two-dimensional square
lattice Holstein
Hamiltonian using numerically exact determinant
quantum Monte Carlo simulations. In particular, we report systematic calculations of the model's single-particle spectral function and optical conductivity over a range of
phonon energies, electron-
phonon coupling strengths, carrier concentrations, and temperatures. In doing so, we map the
evolution of the system from a dressed metallic phase to a (bi)polaron
liquid/
insulator to a charge-density-wave
insulator as the carrier concentration is tuned from dilute values to half-filling. We corroborate these results using several equal-time correlation measurements and related proxy quantities reconstructed from time-displaced correlation measurements. This paper is also accompanied by an extensive open data set, covering over 16,640 unique parameter values.
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All authors J. Neuhaus, B. Cohen-Stead, N. Mannella, S. Johnston
Statistical Mechanics · Cross-listed from hep-th
Landau theory, effective temperature, and tricritical phenomena in a holographic nonequilibrium steady state
Motohiro Kanazawa, Masataka Matsumoto and Shin Nakamura
We investigate the critical exponents $(\gamma,\nu)$ at the current-driven tricritical point (TCP) associated with
chiral symmetry breaking in a nonequilibrium steady state described by the D3/D7 model. In the
symmetry-broken phase, we find that, unlike in the conventional Landau theory, both $\gamma$ and $\nu$ can take values different from those predicted by the Landau theory and depend on the path along which the TCP is approached in the phase diagram. However, when the TCP is approached with the ratio of the effective temperature to the heat bath temperature, $T_{*}/T$, held fixed, the critical exponents agree with those of the Landau theory. These results suggest that the critical phenomena at the current-driven TCP may be described by the Landau theory along the $T_{*}/T$-fixed line, whereas a nontrivial extension of the Landau theory is required for a more general description of the critical phenomena along arbitrary paths.
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Materials Science
Giant Surface-driven Nonlinear Hall Effect in BiTeCl at Room Temperature
Zhihua Liu, Ziheng Wang, Yongbo Lv et al. (+9 more)
The nonlinear
Hall effect (NLHE) provides a pathway to generate a
Hall response in time-reversal-symmetric yet inversion-
symmetry-broken systems. NLHE can rectify an alternating current into a transverse direct voltage, making it attractive for
radio-frequency rectification, energy harvesting, and terahertz detection, applications for which device miniaturization remains a central pursuit. In this context, the inherent inversion
symmetry breaking at surfaces is particularly appealing: because
symmetry is necessarily broken at the surface of any
crystal, irrespective of whether its bulk is centrosymmetric, surface-driven nonlinear responses lift the stringent constraint on bulk
symmetry and open a route toward compact device architectures. Here we report the observation of a
giant, surface-driven second-order nonlinear
Hall effect in the Rashba-type polar
semiconductor BiTeCl at room temperature. The determined second-order nonlinear
Hall susceptibility at 300 K reaches 1.68 $\mu$mV$^{-1}$, which is 80 times larger than that of the best previously reported surface-dominated systems. We attribute this
giant response to the synergistic interplay between BiTeCl's polar
crystal structure and its rich surface states: the polar stacking renders the top and bottom surfaces inequivalent, so that the nonlinear response originates from a single surface without compensation from the other.
Symmetry and scaling analyses suggest that both skew-scattering and side-jump mechanisms contribute to the observed effect. Our findings not only identify BiTeCl as a promising platform for future applications utilizing the NLHE, but also establish the asymmetry between the opposite surfaces of a polar
crystal as a general design principle for discovering surface-driven materials with larger nonlinear
Hall responses.
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All authors Zhihua Liu, Ziheng Wang, Yongbo Lv, Hanru Feng, Zhiwei Zhang, Bo Zhang, Feng Liu, Guohua Wang, Shengwei Jiang, Hao Chu, Hui Li, Dong Qian
Materials Science
Determination of the ferrimagnetic structure of monoclinic TbFe$_{2}$D$_{4.2}$ deuteride and its evolution versus temperature and high magnetic field
Valerie Paul-Boncour and Olivier Isnard
The
magnetic properties of monoclinic TbFe$_{2}$D$_{4.2}$ have been investigated by combining different
magnetic measurements, including those involving a high pulsed
magnetic field, with
neutron diffraction experiments versus temperature and applied field. TbFe$_{2}$D$_{4.2}$ displays a ferrimagnetic ground state with M$_{Tb}$ = 8.2(2) $\mu$$_{B}$ and M$_{Fe}$ = 2.1(2) $\mu$$_{B}$. At 4.2 K a large
magnetic anisotropy related to the Tb moments is observed, as saturation is not reached at 50 T. In addition, two metamagnetic transitions are observed for fields of 3 and 29 T. Upon heating, the Tb moment decreases progressively whereas the Fe moment remains constant up to 150 K. At 160 K both Tb and Fe moments sharply decrease, and a 0.38% contraction of the
cell volume is observed due to an itinerant electron metamagnetic behavior of the Fe sublattice. This transition temperature is 76 K higher than that of YFe$_{2}$D$_{4.2}$ due to an increase in
cell volume, as well as exchange interactions between the Fe and Tb moments. The deuteride becomes paramagnetic above 220 K.
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Strongly Correlated Electrons
Anomalous stabilization of excitons by metallic proximity
Jeongkeun Song, Uksam Choi, Shan Lin et al. (+6 more)
Metallic environments are generally expected to suppress
excitons through strong dielectric screening, yet their influence can differ in composite systems where metallic and insulating regions coexist. Here, we investigate excitonic states in PdxCu1-xCrO2 thin films across a percolation-driven metal-
insulator transition. Optical spectroscopy and many-body GW calculations show that CuCrO2 hosts strongly bound
excitons with a binding energy of about 489 meV. With increasing Pd substitution, the system approaches an
insulator-to-metal transition near x = 0.5, consistent with the site-percolation threshold of a triangular
lattice. In the pre-percolation regime, the excitonic resonance
redshifts by 241 meV while the Tanguy continuum onset remains nearly unchanged, consistent with a substantial increase in
exciton binding energy before metallization. An image-charge-based excitonic hydrogen model shows that isolated metallic regions can enhance electron-hole binding through image-charge interactions, whereas conventional screening is recovered once a continuous metallic network forms. Although this model provides a possible interpretation of the observed excitonic
evolution, an alternative scenario in which metallic and excitonic responses originate from electronically distinct states and evolve independently cannot be excluded. These results reveal unusual metallic-excitonic coexistence near a percolation-driven metal-
insulator transition and suggest nanoscale metallic proximity as a possible route for modifying excitonic interactions.
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All authors Jeongkeun Song, Uksam Choi, Shan Lin, Du Li, Baekjune Kang, Li Yang, Ambrose Seo, Changhee Sohn, Ho Nyung Lee
Materials Science
Absence of lateral domain wall mobility in Zn1-xMgxO thin films
Jack Eckstein, Kyle P. Kelley, William Prudnick et al. (+4 more)
Polarization reversal in ferroelectrics arises from the coupled processes of domain nucleation and subsequent growth, yet the governing mechanisms differ fundamentally between classical perovskite
oxides and emerging wurtzite ferroelectrics. While switching in perovskites is typically governed by mobile domain walls whose field-driven propagation dominates macroscopic kinetics, here we show that polarization reversal in wurtzite Zn1-xMgxO proceeds through a qualitatively different pathway. Using scanning oscillator microscopy, in combination with point pulse-imaging methods, we directly map local switching events and domain wall responses, revealing that domain walls in Zn1-xMgxO exhibit negligible lateral mobility (sub 10nm) and that polarization reversal proceeds predominantly through the nucleation of vertically extended columnar filaments with a lateral size on the order of the grains. This nucleation-controlled switching contrasts sharply with the growth-mediated dynamics characteristic of perovskite ferroelectrics and explains the abrupt, spatially localized switching behavior observed in wurtzite systems. These results establish nucleation-dominated filamentary reversal as a defining switching mechanism in Zn1-xMgxO and point towards the need for further studies to understand correlation lengths and nucleation processes across a range of grain sizes.
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All authors Jack Eckstein, Kyle P. Kelley, William Prudnick, Jon-Paul Maria, Stephen Jesse, Neus Domingo, Rama K. Vasudevan