Superconductivity
Contrasting Momentum-Selective Spin-Density-Wave Gaps in Bilayer and Trilayer Nickelates
Jun Shu, Jun Shen, Xiaoxiang Zhou et al. (+12 more)
Resolving where the density-wave gap opens in momentum space is essential for identifying the microscopic origin of the instability in layered nickelates. Using polarization-resolved electronic Raman scattering, we map the momentum selectivity of the
spin-density-wave (SDW) gap in trilayer La4Ni3O10. We observe a SDW-induced redistribution of spectral weight on both the $\alpha$ pocket at the Brillouin-zone centre and a portion of the $\beta$ pocket near the zone boundary, characterized by gap energies of approximately 55~meV. In contrast, no comparable spectral weight suppression is observed along the diagonal region of $\beta$ pockets, implying little or no gap opening. This gap
topology contrasts sharply with that in La3Ni2O7, where anisotropic SDW gaps open solely on the $\beta$ pocket. Our results establish a distinct momentum-space gap
topology between
bilayer and trilayer nickelates, placing new constraints on the ordering wave vector and the mechanism of the density-wave instability relevant to superconductivity.
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All authors Jun Shu, Jun Shen, Xiaoxiang Zhou, Yinghao Zhu, Qingsong Wang, Dengjing Wang, Weihong He, Jie Yuan, Kui Jin, Dawei Shen, Congcong Le, Jun Zhao, Zengyi Du, Ge He, Donglai Feng
Strongly Correlated Electrons
The Dose Makes the Poison: Perturbative Steps Toward the Ultimate Linearized Coupled Cluster Method
Sylvia J. Bintrim, Ella R. Ransford and Kevin Carter-Fenk
"Addition-by-subtraction" coupled cluster (CC) approaches provide a promising approach to treating the difficult strong correlation problem by simplifying the standard CC equations. In a separate vein, linearized CC methods have drawn interest for their lower computational cost, increased parallelizability, and favorable properties for extension to the excited state–but the inclusion of ring/crossed-ring terms causes singularities even for single bond breaking. A linearized, addition-by-subtraction CC method called linearized ladder CCD (linLCCD) removes these terms to avoid divergences, but linLCCD under-estimates dynamical correlation. Herein we resolve this deficiency of linLCCD by introducing a linearized external coupled cluster perturbation theory that adds a second-order ring/crossed-ring correction back into a linLCCD reference wave function. Our resultant xlinCCD(2) method is regular and yields comparable results to linearized CCD in weakly-correlated regimes.
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Mesoscale and Nanoscale Physics
Viscous Electron Flow and Nonlinear Magnetotransport in 2D Channels
A. D. Levin, G. M. Gusev and A. K. Bakarov
We examine nonlinear transport in a viscous two-dimensional electron fluid within narrow GaAs channels. The differential magnetoresistance shows nonmonotonic behavior, a signature of electron pairing in the hydrodynamic regime. Theoretical models that account for both the influence of these interactions on shear stress relaxation and viscosity changes from electron heating show good agreement with the data. The nonlinear regime thus reveals how such correlated states govern the hydrodynamic behavior of the electron fluid. Our findings establish the nonlinear transport regime as a powerful probe for dissecting the complex interplay of correlated electron states and momentum relaxation in the hydrodynamic flow of an electron fluid.
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Superconductivity
Direct Observation of Unidirectional Density Wave and Band splitting in a Single-Domain Trilayer Nickelate Pr$_4$Ni$_3$O$_{10}$
Zhicheng Jiang, Enkang Zhang, Yuxin Wang et al. (+12 more)
Unraveling the interplay between density-wave (DW) instabilities and multi-orbital physics is critical for understanding superconductivity in Ruddlesden-Popper nickelates, yet intrinsic electronic features have been persistently obscured by material inhomogeneity and thus the multi-domain averaging effect. Here, we employ micro-focused angle-resolved photoemission spectroscopy ($\mu$-ARPES) on single-domain Pr$_4$Ni$_3$O$_{10}$ to disentangle the complex hierarchy of intrinsic and back-folded bands, explicitly identifying the electronic states driving the DW phase transition. We provide decisive spectroscopic evidence that the low-energy reconstruction is governed by inter-orbital nesting between the $\alpha$ and $\beta$ bands. Specifically, we resolve a orbital-dependent gap of $\sim44$ meV on the $\alpha$ pocket, a value quantitatively consistent with prior measurements, unifying previously conflicting experimental reports regarding the locus and magnitude of the DW gap. Furthermore, we reveal strong orbital-selective mass renormalization in the $d_{z^2}$ states and successfully resolve the long-sought intrinsic trilayer $\beta$-band splitting, establishing a critical lower bound for the outer-layer hopping. These results define a coherent microscopic fingerprint for the trilayer nickelates, identifying the specific nesting channels and correlation effects that underpin the phase diagram.
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All authors Zhicheng Jiang, Enkang Zhang, Yuxin Wang, Zhengtai Liu, Jishan Liu, Runfeng Zhang, Xinnuo Zhang, Wenchuan Jing, Yu Huang, Qi Jiang, Mao Ye, Kun Jiang, Jun Zhao, Dawei Shen, Donglai Feng
Disordered Systems and Neural Networks
Machine-Learned Hamiltonians for Quantum Transport Simulation of Valence Change Memories
Chen Hao Xia, Manasa Kaniselvan, Marko Mladenoivić et al. (+1 more)
The construction of the
Hamiltonian matrix H is an essential, yet computationally expensive step in ab-initio device simulations based on density-functional theory (DFT). In homogeneous structures, the fact that a unit
cell repeats itself along at least one direction can be leveraged to minimize the number of atoms considered and the calculation time. However, such an approach does not lend itself to amorphous or defective materials for which no periodicity exists. In these cases, (much) larger domains containing thousands of atoms might be needed to accurately describe the physics at play, pushing DFT tools to their limit. Here we address this issue by learning and directly predicting the
Hamiltonian matrix of large structures through equivariant graph neural networks and so-called augmented partitioning training. We demonstrate the strength of our approach by modeling valence change
memory (VCM)
cells, achieving a Mean Absolute Error (MAE) of 3.39 to 3.58 meV, as compared to DFT, when predicting the
Hamiltonian matrix entries of systems made of $\sim$5,000 atoms. We then replace the DFT-computed
Hamiltonian of these VCMs with the predicted one to compute their energy-resolved transmission function with a
quantum transport tool. A qualitatively good agreement between both sets of curves is obtained. Our work provides a path forward to overcome the
memory and computational limits of DFT, thus enabling the study of large-scale devices beyond current ab-initio capabilities
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All authors Chen Hao Xia, Manasa Kaniselvan, Marko Mladenoivić, Mathieu Luisier
Mesoscale and Nanoscale Physics
Intersubband electric dipole spin resonance in transition metal dichalcogenide heterobilayers
K.K. Grigoryan and M.M. Glazov
The theory of inter-
spin-subband electric dipole
spin resonance in transition metal dichalcogenide heterobilayers is proposed. Our
symmetry analysis demonstrates that, in contrast to monolayers, the reduced
symmetry of heterobilayers enables coupling between conduction band
spin subbands by an electric field. We establish the optical selection rules for all six high-
symmetry stacking configurations. The microscopic mechanism of the effect is identified as the
spin-orbit coupling induced mixing of Bloch states from different conduction bands, which generates a non-zero momentum
matrix element between the
spin-split states. It also leads to the linear-in-wavevector
spin-dependent terms in the effective
Hamiltonian, i.e., the Rashba effect. Our estimates show that the rate of electric-dipole
spin-flip transitions exceeds by far that of the
magnetic-dipole transitions in transition metal dichalcogenide heterobilayers.
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Strongly Correlated Electrons · Cross-listed from quant-ph
A Schwinger-Keldysh Formulation of Semiclassical Operator Dynamics
Jeff Murugan and Hendrik J. R. van Zyl
In this work we develop a real-time Schwinger-Keldysh formulation of Krylov dynamics that treats Krylov complexity as an in-in observable generated by a closed time contour path integral. The resulting generating functional exposes an emergent phase-space description in which the Lanczos coefficients define an effective
Hamiltonian governing operator motion along the Krylov chain. In the semiclassical limit, exponential complexity growth arises from
hyperbolic trajectories, and asymptotically linear Lanczos growth appears as a universal chaotic fixed point, with sub-leading deformations classified as irrelevant, marginal or relevant. Going beyond the saddle, the Schwinger-Keldysh framework provides controlled access to fluctuations and large deviations of Krylov complexity, revealing sharp signatures of integrability-chaos crossovers that are invisible at the level of the mean. This formulation reorganises Krylov complexity into a dynamical field-theoretic framework and identifies new fluctuation diagnostics of operator growth in closed
quantum systems.
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Mesoscale and Nanoscale Physics
Microscopic simulations of the coupled dynamics of cavity photons, excitons, and biexcitons
Hendrik Rose, Stefan Schumacher and Torsten Meier
The coherent interaction between
quantum light and material excitations in
semiconductor nanostructures is investigated using a fully quantized microscopic approach that incorporates many-body Coulomb correlations. The simulations demonstrate that the
quantum dynamics is influenced by biexciton continuum states and is highly sensitive to both the frequency of the cavity mode and the strength of the light-matter coupling.
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Quantum Gases
Nonreciprocity Induced Fractional Nonlinear Thouless Pumping
Yanqi Zheng, Kun Pu, Ligging Ren et al. (+2 more)
Recent interest has surged in
eigenvalue's nonlinearity-based topological transport governed by the equation of auxiliary
eigenvalues $H\Psi=\omega S(\omega)\Psi$ [T. Isobe et al., Phys. Rev. Lett. 132, 126601 (2024); C. Bai and Z. Liang, 111, 042201 (2025); Phys. Rev. A 112, 052207 (2025)] rather than the conventional Schrodinger equation $H\Psi=E\Psi$ in conservative settings, yet non-Hermitian generalizations remain uncharted. In this work, we are motivated to investigate the nonlinear Thouless pumping in a non-Hermitian and nonlinear Rice-Mele model. In particular, we uncover how non-Hermiticity parameters can induce fractional topological phases–even in the presence of quantized topological invariants as predicted by conventional linear approaches. Crucially, these fractional phases are naturally explained within the framework of the equation of auxiliary
eigenvalues, directly linking nonlinear spectral characteristics to the bulk-boundary correspondence. Our findings reveal novel emergent phenomena arising from the interplay between nonlinearity and non-Hermiticity, providing key insights for the design of topological
insulators and the controlled manipulation of
quantum edge states in the real world.
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All authors Yanqi Zheng, Kun Pu, Ligging Ren, Chenxi Bai, Zhaoxin Liang
Superconductivity
Two-lifetime model for the cuprates revisited
František Herman, Lucia Gelenekyová, Hana Havranová et al. (+1 more)
Several models of the strange-metal state of the cuprate
superconductors postulate the existence of strong inelastic forward scattering of the electrons, but direct evidence of such scattering is missing. Here we show that angle-resolved photoemission spectroscopy (ARPES) provides a unique tool which can address this issue. We propose a two-lifetime phenomenological model of the superconducting state of the cuprates and we show that it explains several salient low-energy features of the measured ARPES spectra. The model enables discrimination between forward- and large-angle scattering and, in addition, gives access to the magnitude of the gap function away from the
Fermi surface.
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All authors František Herman, Lucia Gelenekyová, Hana Havranová, Richard Hlubina
Statistical Mechanics
Mandelbrot, Financial Markets and the Origins of "Econophysics"
Jean-Philippe Bouchaud
This text revisits the origins of econophysics through the figure of Benoît Mandelbrot, not as the father of fractals, but as the instigator of a distinctive scientific posture. The guiding thread is methodological: accept the stubborn features of the data and use models as instruments for intuition rather than as axiomatic certificates of truth. In this perspective, scaling, intermittency and extremes are not peripheral imperfections around a well-behaved
equilibrium; they are the very texture of economic and financial fluctuations. This naturally shifts
attention from exogenous narratives to endogenous dynamics: interactions, feedback loops, and collective amplification mechanisms that can make systems intrinsically fragile. We argue that the importation of concepts from statistical physics – criticality, disorder, emergence, multiplicative cascades – should be read not as an artificial transposition but as a candid attempt to look for generic mechanisms compatible with empirical regularities observed across scales, from
markets to macroeconomic aggregates.
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Mesoscale and Nanoscale Physics · Cross-listed from hep-th
The soliton nature of the super-Klein tunneling effect
Francisco Correa, Luis Inzunza and Olaf Lechtenfeld
We establish a relationship between the Davey–Stewartson II (DS II) integrable system in $(2{+}1)$ dimensions and quasi-exactly solvable planar interacting Dirac
Hamiltonians that exhibit the super-Klein tunneling (SKT) effect. The Dirac interactions are constructed from the real and imaginary parts of breather solutions of the DS II system. In this framework, the SKT effect arises when the energy is tuned to match the constant background of the
soliton, while the resulting Dirac
Hamiltonians simultaneously support bound states embedded in the continuum. By imposing the SKT boundary conditions, we employ Darboux transformations to construct a general three-parameter family of DS II breather solutions that can be mapped to Dirac
Hamiltonians. At the initial
soliton time, the corresponding Dirac systems form a massless two-parameter family of Hermitian models with nontrivial electrostatic potentials. As the
soliton time evolves, the systems become $\mathcal{PT}$-symmetric and develop a nontrivial imaginary mass term. Finally, when the
soliton time is taken to be imaginary, the construction yields Hermitian Dirac systems that lack time-reversal
symmetry. In all cases, we identify the emergence of quasi-
symmetry transformations that preserve the SKT subspace of states while not commuting with the full
Hamiltonian.
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Mesoscale and Nanoscale Physics
Yasser Saleem and Moritz Cygorek
We present a fully atomistic approach to
exciton-
phonon coupling in
semiconductor quantum dots that bridges microscopic electronic-structure calculations with non-Markovian open-
quantum-system dynamics. On the example of an InAsP
quantum dot embedded in an InP
matrix, we compute single-particle states using an ab initio-parametrized tight-binding model, then obtain correlated many-body wave functions of neutral
excitons, biexcitons, and charged trions via the configuration-interaction method. Using these correlated states, we compute the
exciton-
phonon coupling
matrix elements. The resulting
phonon spectral densities for different excitonic complexes are compared with the widely used analytical super-Ohmic form and reveal deviations at higher energies originating from the realistic dot geometry and atomistic wave functions, whereas configuration mixing is found to play only a minor role. Furthermore, we extract radiative lifetimes comparable to values experimentally measured. As a direct application, we simulate the emission brightness of a pulsed-driven
quantum dot and demonstrate that the atomistically derived spectral density substantially broadens the region of efficient off-resonant excitation compared to the analytical model. The presented framework provides a nearly parameter-free route to simulate the non-Markovian open
quantum dynamics in
semiconductor quantum dots.
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Mesoscale and Nanoscale Physics
Topological superconducting phase in a non-Hermitian Kitaev chain with staggered pairing imbalance
Xiao-Jue Zhang, Rong Lü and Qi-Bo Zeng
We introduce a one-dimensional non-Hermitian Kitaev chain with staggered imbalance in the $p$-wave superconducting pairing. By tuning the chemical potential and the pairing imbalance, we find that the eigenenergy spectrum undergoes real-to-complex transitions, and the spectral gap can change from a real to an imaginary one. The pairing imbalance significantly enlarges the parameter region supporting a topological superconducting phase. Remarkably, we show that a topologically nontrivial phase hosting Majorana zero modes can be induced by varying the pairing imbalance, even in the regime of strong chemical potential. The gap-closing points and phase boundaries are determined analytically, and the resulting phase diagrams are presented with the nontrivial phase characterized by a nonzero topological invariant. Furthermore, we identify the coexistence of Majorana zero modes and finite-energy Majorana edge modes in this system. Our results reveal exotic phenomena arising from imbalanced pairing and establish a platform for exploring topological superconductivity in non-Hermitian systems.
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Statistical Mechanics
Longjun Xiang, Jinxiong Jia and Jian Wang
Quantum geometry has been extensively linked to charge,
spin, orbital, and thermal transport in crystalline solids, but its imprint on
entropy transport remains largely unexplored. Here we develop a
quantum theory of
entropy transport for Bloch electrons under an electric field. {Within the relaxation-time approximation, we show that the leading and subleading contributions to
entropy production reproduce the Joule heating relation, with the former arising from the linear Drude current and the latter from the nonlinear Drude current and the intrinsic nonlinear Ohmic current. Microscopically, near topological Dirac band crossings and anticrossings, these contributions are controlled by the
quantum metric and the fully symmetrized
quantum metric dipole, respectively. We further predict a Berry-
curvature-induced
entropy Hall effect, which, together with the local heat
Hall current, provides a simple way to recover the modern theory of orbital magnetization.} Finally, we derive general relations between
entropy and charge currents, offering a practical route to probe
entropy flow experimentally.
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Mesoscale and Nanoscale Physics
Spin Hall and Edelstein effects in a ballistic quantum dot with Rashba spin-orbit coupling
Alfonso Maiellaro, Francesco Romeo, Mattia Trama et al. (+11 more)
We study
spin-resolved transport in a ballistic
quantum dot with Rashba
spin-orbit coupling, focusing on charge-to-
spin conversion and
spin Hall effect. In the regime where the dot size is comparable to the
Fermi wavelength, we identify a clear crossover from weak localization to weak antilocalization as the Rashba coupling increases. This transition is accompanied by gate-tunable
spin currents of Edelstein and
spin Hall type, whose behavior reflects the underlying electron wavefunction interference. Notably, the Edelstein current shows an inflection point at the critical Rashba strength, signaling the crossover from weak localization to weak antilocalization. In the presence of an in-plane
magnetic field we also report a transition in angular periodicity of the magnetoresistance – from $\pi$ to $2\pi$ – arising from the interplay between
spin-orbit interaction and Zeeman coupling. These results establish a direct link between
quantum coherence, charge-to-
spin conversion, and
geometric confinement in mesoscopic systems.
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All authors Alfonso Maiellaro, Francesco Romeo, Mattia Trama, Jacopo Settino, Claudio Guarcello, Carmine Antonio Perroni, Pawel Wójcik, Bartłomiej Szafran, Daniela Stornaiuolo, Marco Salluzzo, Thomas Sand Jespersen, Nicolas Bergeal, Manuel Bibes, Roberta Citro
Disordered Systems and Neural Networks
Putting machine learning to the test in a quantum many-body system
Yilun Gao, Alberto Rodríguez and Rudolf A. Römer
Quantum many-body systems pose a formidable computational challenge due to the exponential growth of their
Hilbert space. While machine learning (ML) has shown promise as an alternative paradigm, most applications remain at the proof-of-concept stage, focusing narrowly on energy estimation at the lower end of the spectrum. Here, we push ML beyond this frontier by extensively testing HubbardNet, a deep neural network architecture for the Bose-Hubbard model. Pushing improvements in the optimizer and learning rates, and introducing physics-informed output activations that can resolve extremely small wave-function amplitudes, we achieve ground-state energy errors reduced by orders of magnitude and wave-function fidelities exceeding 99%. We further assess physical relevance by analysing generalized inverse participation ratios and multifractal dimensions for ground and excited states in one and two dimensions, demonstrating that optimized ML models reproduce localization, delocalization, and multifractality trends across the spectrum. Crucially, these qualitative predictions remain robust across four decades of the interaction strength, e.g. spanning across superfluid, Mott-insulating, as well as
quantum chaotic regimes. Together, these results suggest ML as a viable qualitative predictor of many-body structure, complementing the quantitative strengths of exact diagonalization and tensor-network methods.
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Strongly Correlated Electrons · Cross-listed from hep-th
Shear subdiffusion in non-relativistic holography
Yan Liu, Zhi-Ling Wang and Xin-Meng Wu
We study shear fluctuations in non-relativistic
holographic systems coupled to torsional Newton-Cartan geometry, using asymptotically Lifshitz spacetimes in Einstein-Maxwell-dilaton
gravity. We identify a universal subdiffusive shear mode characterized by the quartic dispersion relation $\omega=-iD_4 k^4$, in sharp contrast to the conventional hydrodynamic
diffusion. We derive this result analytically through a systematic higher-order matched asymptotic expansion connecting near-horizon and far-region solutions, and we verify it with direct numerical quasinormal mode calculations. Our numerics demonstrate that the first non-hydrodynamic mode is purely imaginary and gapped, following the dispersion relation $\omega=-i\omega_0-i D k^2$, and that both the hydrodynamic and the first non-hydrodynamic modes pass through pole-skipping points. These results highlight Lifshitz holography as an efficient framework for anomalous transport in strongly coupled non-relativistic
quantum matter.
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Materials Science
Optical properties of Fermi polarons in a GaInP/MoSe2 monolayer heterostructure
Hangyong Shan, Max Waldherr, Diksha Diksha et al. (+15 more)
Engineering optical properties, such as luminescence purity and charge transfer, is crucial for harnessing the application potential of atomically thin transition metal dichalcogenides (TMDCs). While electrostatic gating is widely applied to gain charge control in TMDC monolayers, charge transfer can also be engineered via coupling of TMDC monolayers at
semiconductor III/V, organic, or van der Waals interfaces. This confers great advantages, such as ease in implementation and compatibility in device integration. Here, we shed light on the optical properties of many-particle complexes emerging at the GaInP/MoSe2 interface as a highly relevant material combination to manipulate the optical properties of TMDCs in integrated photonic devices. Our study verifies its nature as a type II hetero-interface, which bears the feasibility to display disorder-free photoluminescence. Through optical absorption measurements, we verify that the charged complexes acquire substantial oscillator strength. Furthermore, temperature-dependent photoluminescence, supported by a microscopic theory framework, evidences the suppression of the characteristic carrier
recoil effect that was previously observed in the photoluminescence of trions in TMDCs. These phenomena allow us to identify the optical signatures at the TMDC-GaInP interface as
Fermi polaron quasiparticle resonances, which are of high importance in researching Bose-
Fermi mixtures in condensed matter systems.
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All authors Hangyong Shan, Max Waldherr, Diksha Diksha, Ghada Missaoui, Seyma Esra Atalay, Martin Zinner, Ana Maria Valencia, Kenji Watanabe, Takashi Taniguchi, Seth Ariel Tongay, Caterina Cocchi, Brendan C. Mulkerin, Jesper Levinsen, Francesca Maria Marchetti, Meera M. Parish, Niklas Nilius, Christian Schneider, Sven Höfling
Quantum Gases
Strong Correlations in the Dynamical Evolution of Lowest Landau Level Bosons
Yuchen Yang and Nigel R. Cooper
Recent experiments with rotating Bose gases have demonstrated the interaction-driven hydrodynamic instability of an initial extended strip-like state in the lowest Landau level. We investigate this phenomenon in the low density limit, where the mean-field Gross–Pitaevskii theory becomes inadequate, using exact diagonalisation studies and analytic arguments. We show that the behaviour can be understood in terms of weakly-interacting repulsively-bound few-body clusters. Signatures of cluster behaviour are observed in the expectation values of observables which oscillate at frequencies characterised by the energies of few-body boundstates. Using a semiclassical theory for interacting clusters, we predict the long-time growth of the cloud width to be a power law in the logarithm of time. This slow thermalisation of bound clusters represents a form of
quantum many-body scars.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Universal scaling of finite-temperature quantum adiabaticity in driven many-body systems
Li-Ying Chou and Jyong-Hao Chen
Establishing quantitative adiabaticity criteria at finite temperature remains substantially less developed than in the pure-state setting, even though realistic
quantum systems are never at absolute zero. Here, by combining a mixed-state
quantum speed limit with mixed-state fidelity susceptibility within the Liouville-space formulation of
quantum mechanics, we derive rigorous bounds on the
Hilbert-Schmidt fidelity between mixed states. Focusing on protocols that drive an initial Gibbs state toward a quasi-Gibbs target, these bounds yield an explicit threshold driving rate for the onset of nonadiabaticity. For a broad class of local
Hamiltonians in gapped phases, we show that, in the thermodynamic limit, the threshold driving rate factorizes into a system-size contribution that recovers the zero-temperature scaling and a universal temperature-dependent factor. The latter is exponentially close to unity at low temperature, whereas at high temperature it is linear in temperature. We verify the predicted scaling in several
spin-1/2 chains by obtaining closed-form expressions for the threshold driving rate. Our results provide a practical and largely model-independent criterion for finite-temperature adiabaticity in driven many-body systems under closed-system
unitary evolution.
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Materials Science
FluxNet: Learning Capacity-Constrained Local Transport Operators for Conservative and Bounded PDE Surrogates
Zishuo Lan, Junjie Li, Lei Wang et al. (+1 more)
Autoregressive learning of time-stepping operators provides an effective approach to data-driven partial differential equation (PDE) simulation, yet for conservation laws, they face a fundamental challenge: learned updates may violate global conservation over long rollouts. For the important subclass of mass-conservation-type equations, the problem is compounded by inherent physical bounds (e.g., nonnegativity or concentrations in [0,1]) whose violation further destabilizes predictions. We introduce FluxNet, which learns cumulative transport amounts representing the total conserved quantity redistributed between each
cell and a configurable neighborhood over the full surrogate interval. A conservative update guarantees exact discrete conservation by construction; modular capacity-constrained transport heads (L, U, and D) enforce lower bounds, upper bounds, or near-zero dual-bound violations through architectural design. Unlike flux-rate surrogates that require temporal integration and thus inherit CFL constraints, FluxNet involves no such integration; configurable transport neighborhoods enable large-timestep prediction at full spatial resolution. Ghost
cells extend the framework to non-periodic boundaries. Experiments on four
benchmarks (1D convection–
diffusion, 2D shallow water, 1D traffic flow, 2D Cahn–Hilliard) demonstrate exact conservation, structural bound preservation, architecture modularity, and superior stability over flux-rate surrogates at large temporal strides. The code is publicly available at: https://github.com/Lan-zs/FluxNet.
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All authors Zishuo Lan, Junjie Li, Lei Wang, Jincheng Wang
Materials Science
Fe-DCA Metal-Organic Frameworks on the Bi2Se3(0001) Topological Insulator Surface
Anna Kurowská, Jakub Planer, Pavel Procházka et al. (+6 more)
The formation of two-dimensional metal-organic frameworks (MOFs) on an inert surface of a topological
insulator (TI) is a pathway to engineer
quantum materials with exotic properties. MOFs featuring ferromagnetically coupled metal atoms are theoretically predicted to induce an exchange gap in the TI surface band structure, potentially leading to a
quantum anomalous
Hall effect. However, achieving ordered MOFs on TI surfaces remains challenging due to the limited knowledge of self-assembly on these substrates. In this paper, we demonstrate self-assembly of Fe atoms and dicyanoanthracene (DCA) molecules into 2D MOFs on the Bi2Se3(0001) surface at room temperature, investigated via a combination of low-energy electron microscopy and diffraction (LEEM/LEED), scanning tunneling microscopy (STM), and ab initio calculations based on density functional theory (DFT). Two competing Fe-DCA phases form. The first phase corresponds to a close-packed Fe1DCA3 structure. In contrast, the second phase exhibits a larger unit
cell with no match to either known or DFT-calculated systems, indicating a more complex bonding environment. These findings advance the understanding of the growth of MOFs on a strong topological
insulator surface and provide insights for designing MOFs/TI interfaces with tailored electronic and
magnetic properties.
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All authors Anna Kurowská, Jakub Planer, Pavel Procházka, Veronika Stará, Elena Vaníčková, Zdeněk Endstrasser, Matthias Blatnik, Čestmír Drašar, Jan Čechal
Statistical Mechanics
Internal Trajectories and Observation Effects in Langevin Splitting Schemes
Bettina G. Keller
Langevin integrators based on operator splitting are widely used in molecular dynamics. This work examines Langevin splitting schemes from the perspective of their internal trajectories and observation points, complementing existing generator-based analyses. By exploiting merging, splitting, and cyclic permutation of elementary update operators, formally distinct schemes can be grouped according to identical or closely related trajectories. Accuracy differences arising from momentum updates and observation points are quantified for configurational sampling, free-energy estimates, and transition rates. While modern Langevin integrators are remarkably stable under standard simulation conditions, subtle but systematic biases emerge at large friction coefficients and time steps. These results clarify when accuracy differences between splitting schemes matter in practice and provide an intuitive framework for understanding observation effects.
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Materials Science
Thermophysical properties of spark plasma sintered UCo: a comparison with machine learning predictions
Yifan Sun, Hironobu Nakamura, Masaya Kumagai et al. (+2 more)
Uranium dioxide has been widely used as a
nuclear fuel in commercial light water reactors due to its high uranium density and chemical stability. However, its relatively low thermal conductivity is not optimal from the viewpoints of fuel integrity and safety margins, particularly during loss-of-coolant accidents. Although the development of accident-tolerant fuels with higher thermal conductivity is strongly desired, many potential uranium compounds remain unexplored due to constraints associated with handling radioactive materials. To efficiently screen promising uranium compounds with high thermal conductivity, past studies have leveraged machine-learning models to accelerate the discovery process. In this study, we experimentally examine the model's predictions by fabricating UCo and measuring its high-temperature thermophysical properties. Our results show that the thermal conductivity of UCo predicted by machine learning is in good agreement with the experimental measurements. Despite slight discrepancies, additional SHAP analysis suggests that the model's decision logic is consistent with known physical trends. Overall, this study fills a gap in reported thermophysical properties of UCo and provides experimental support for machine-learning-assisted screening of uranium compounds relevant to advanced fuel development.
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All authors Yifan Sun, Hironobu Nakamura, Masaya Kumagai, Yuji Ohishi, Ken Kurosaki
Quantum Gases
Quantum vortex channels as Josephson junctions
Natalia Masalaeva, Wyatt Kirkby, Francesca Ferlaino et al. (+1 more)
In
quantum gases, weak links are typically realized with externally imposed optical potentials. We show that, in rotating binary condensates, quantized
vortices in one component form hollow channels that act as self-induced weak links for the other, enabling superflow through otherwise impenetrable, phase-separated domains. This introduces a novel barrier mechanism:
quantum pressure creates an effective barrier inside the
vortex channel, set by the constriction width, which controls the superflow. Tuning the interspecies interaction strength drives a crossover from the hydrodynamic transport to Josephson tunneling regime. Long-range dipolar interactions further tune the weak-link properties, enabling both short links and two coupled junctions in series.
Circuit models quantitatively capture the dc current-phase relations for both configurations. These results establish
vortices as reconfigurable, interaction-controlled Josephson elements in superfluids.
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All authors Natalia Masalaeva, Wyatt Kirkby, Francesca Ferlaino, Russell N. Bisset
Materials Science
Bayesian Parameter Estimation for Predictive Modeling of Illumination-Dependent Current-Voltage Curves
Eunchi Kim and Thomas Kirchartz
Machine learning enables rapid estimation of material parameters in
solar cells via neural-network-based surrogate models. However, the reliability of extracted parameters depends on underlying assumptions such as the choice of one-dimensional drift-
diffusion model and selection of free material parameters. To validate the inferred parameters, we perform predictive modeling of light-intensity-dependent current-voltage (JV) characteristics. Well-known physical effects, including the influence of external resistance and recombination dynamics on illumination-dependent device performance, are reflected in parameter estimation and prediction workflow. We show that correct treatment of dark shunt resistance and emphasizing shifted current (J + Jsc) during fitting enhances prediction accuracy at low to intermediate illumination level. Additionally, we analyze the information content of various input JV curve combinations, demonstrating that including at least one illuminated JV, preferably not under high illumination due to series resistance effects, is critical for reliable parameter estimation and device performance prediction.
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Mesoscale and Nanoscale Physics
Weyl-Dirac nodal line phonons with type-selective surface states
Le Du, Zeling Li, Jiabing Chen et al. (+3 more)
The band complex formed by multiple topological states has attracted extensive
attention for the emergent properties produced by the interplay among the constituent states. Here, based on group theory analysis, we present a scheme for rapidly identifying the Weyl-Dirac nodal lines (a complex of Weyl and Dirac nodal lines) in bosonic systems. We find only 5 of the 230 space groups host Weyl-Dirac nodal line
phonons. Notably, the Dirac nodal line resides along the high-
symmetry line, whereas the Weyl nodal line is distributed on the high-
symmetry plane and is interconnected with the Dirac nodal line, jointly forming a composite nodal network structure. Unlike traditional nodal nets, this nodal network exhibits markedly distinct surface states on different surfaces, which can be attributed to the fundamental differences in the topological properties between the Weyl and Dirac nodal lines. This unique property thus allows the material to present distinct surface states in a termination-selective manner. Furthermore, by first-principles calculations, we identify the materials NdRhO$_{3}$ and ZnSe$_{2}$O$_{5}$ as candidate examples to elaborate the Weyl-Dirac nodal line and their related topological features. Our work provides an insight for exploring and leveraging topological properties in systems with coexisting multiple topological states.
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All authors Le Du, Zeling Li, Jiabing Chen, Dongliang Mao, Lei Wang, Xiao-Ping Li
Materials Science
Facilitating electrical and laser-induced skyrmion nucleation with a dipolar-field enhanced effective DMI
Mark C. H. de Jong, Dinar Khusyainov, Julian Hintermayr et al. (+6 more)
We demonstrate experimentally how the nucleation of skyrmions in an Ir, Co, and Pt based
magnetic multilayer is affected by introducing a layer dependent sign for the Dzyaloshinskii-Moriya interaction (DMI). In one stack, the bottom half of the stack is given a positive DMI and the top half a negative DMI, and as a result, the in-plane component of the dipolar field is aligned parallel to the effective field of the DMI in every layer, enhancing the effective DMI. We show that this enhanced DMI facilitates the nucleation and stability of skyrmions using both current-driven and
laser-induced skyrmion nucleation. In the devices with an enhanced effective DMI, the density of nucleated skyrmions is greater by up to a factor 20 and skyrmions can be observed in stronger
magnetic fields - suggesting that their stability is also improved. These results show that skyrmion nucleation depends strongly on the magnitude of the effective DMI in a
magnetic multilayer and that the dipolar field within such a multilayer presents an effective route towards controlling the effective DMI, and thereby, the nucleation of
chiral magnetic textures.
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All authors Mark C. H. de Jong, Dinar Khusyainov, Julian Hintermayr, Bart Sanders, Dmitry Kozodaev, Aleksei V. Kimel, Bert Koopmans, Theo H. M. Rasing, Reinoud Lavrijsen
Statistical Mechanics · Cross-listed from quant-ph
Finite-Size Scaling of the Full Eigenstate Thermalization in Quantum Spin Chains
Yuke Zhang and Pengfei Zhang
Despite the
unitary evolution of closed
quantum systems, long-time expectation of local observables are well described by thermal ensembles, providing the foundation of
quantum statistical mechanics. A promising route to understanding this
quantum thermalization is the eigenstate thermalization hypothesis (ETH), which posits that individual energy eigenstates already appear locally thermal. Subsequent studies have extended this concept to the full ETH, which captures higher-order correlations among
matrix elements through nontrivial relations. In this work, we perform a detailed exact-diagonalization study of finite-size corrections to these relations in the canonical ensemble. We distinguish two distinct sources of corrections: those arising from energy fluctuations, which decay polynomially with system size, and those originating from fluctuations within each energy window, which decay exponentially with system size. In particular, our analysis resolves the puzzle that, for certain observables, finite-size corrections exhibit anomalous growth with increasing system size even in chaotic systems. Our results provide a systematic and practical methodology for validating the full ETH in
quantum many-body systems.
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