Mesoscale and Nanoscale Physics
Electrodynamics of swift-electron momentum transfer to a large spherical nanoparticle
Jesús Castrejón-Figueroa, Jorge Luis Briseño-Gómez, Eduardo Enrique Viveros-Armas et al. (+2 more)
Swift electrons from highly focused beams produced in aberration-corrected scanning transmission electron microscopes offer a powerful route for probing and manipulating matter at the nanoscale. Although linear momentum transfer from swift electrons to nanoparticles has been investigated theoretically and experimentally, subsequent analyzes revealed that several earlier predictions relied on non-causal dielectric functions or insufficient numerical convergence, leading to spurious sign reversals in the transferred momentum. Here, we derive analytical expressions and develop a numerically efficient electrodynamic framework to compute the linear momentum transferred from a swift electron to an isolated spherical nanoparticle described by a fully causal, local dielectric response. We apply our framework to large nanoparticles with 50 nm radius and explicitly resolve the spectral density of linear momentum transfer across the full frequency domain. Using causal dielectric functions for aluminum and bismuth, we analyze the role of electron velocity, impact parameter, and material-specific resonances. We find that, when causality and full multipolar convergence are enforced, the net transverse linear momentum transferred to spherical nanoparticles remains attractive toward the electron trajectory for all nanoparticles considered, despite the presence of material-dependent sign changes in individual electric and
magnetic contributions. These results contrast with earlier theoretical predictions of net repulsive behavior and indicate that additional physical mechanisms beyond the present isolated, local description are required to account for experimentally observed repulsion. Our work establishes a robust reference framework for momentum transfer calculations and provides quantitative
benchmarks relevant for electron-beam-based nanoscale manipulation.
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All authors Jesús Castrejón-Figueroa, Jorge Luis Briseño-Gómez, Eduardo Enrique Viveros-Armas, José Ángel Castellanos-Reyes, Alejandro Reyes-Coronado
Strongly Correlated Electrons
Machine-learning force-field models for dynamical simulations of metallic magnets
Gia-Wei Chern, Yunhao Fan, Sheng Zhang et al. (+1 more)
We review recent advances in machine learning (ML) force-field methods for Landau-Lifshitz-Gilbert (LLG) simulations of itinerant electron magnets, focusing on scalability and transferability. Built on the principle of locality, a deep neural network model is developed to efficiently and accurately predict the electron-mediated forces governing
spin dynamics.
Symmetry-aware descriptors constructed through a group-theoretical approach ensure rigorous incorporation of both
lattice and
spin-rotation
symmetries. The framework is demonstrated using the prototypical s-d exchange model widely employed in spintronics. ML-enabled large-scale simulations reveal novel nonequilibrium phenomena, including anomalous coarsening of tetrahedral
spin order on the triangular
lattice and the freezing of phase separation dynamics in lightly hole-doped, strong-coupling square-
lattice systems. These results establish ML force-field frameworks as scalable, accurate, and versatile tools for modeling nonequilibrium
spin dynamics in itinerant magnets.
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All authors Gia-Wei Chern, Yunhao Fan, Sheng Zhang, Puhan Zhang
Mesoscale and Nanoscale Physics
Bright-dark exciton splitting in lead halide perovskite crystals accessed via quantum beats in photon echoes
M. Alex Hollberg, Mikhail O. Nestoklon, Artur V. Trifonov et al. (+7 more)
Understanding the fine structure of
excitons is crucial for optoelectronic and
quantum photonic applications of lead halide perovskites. It is demonstrated that polarization-sensitive
photon echo spectroscopy in
magnetic field provides a powerful method to access coherent
exciton dynamics and reveal their energy level structure, which is hidden by inhomogeneous broadening.
Exciton quantum beats observed in both Faraday and Voigt geometries offer a precise probe of the energy splittings among the four 1$s$
exciton states, enabling determination of the fine structure and bright-dark splittings. Application of this technique to bulk mixed halide perovskite
crystals FA$_{0.9}$Cs$_{0.1}$PbI$_{2.8}$Br$_{0.2}$ reveals a bright-dark
exciton splitting of $\Delta_\mathrm{X}=0.46~$meV, along with electron and hole Landé $g$ factors $g_\mathrm{e}=3.38$ and $g_\mathrm{h}=-1.14$, respectively. The
quantum beats persist on timescales of 20–50$~$ps, demonstrating remarkably robust
spin and optical coherences at cryogenic temperature of 2$~$K. The decay of the
quantum beats of the outer doublet is governed by dephasing due to dispersion of the bright-dark splitting of $\sim0.06~$meV caused by localization potential fluctuations, while dephasing in the bright
exciton inner doublet originates from a small zero field splitting of $\sim0.035~$meV due to anisotropic potentials.
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All authors M. Alex Hollberg, Mikhail O. Nestoklon, Artur V. Trifonov, Stefan Grisard, Oleh Hordiichuk, Dmitry N. Dirin, Maksym V. Kovalenko, Dimitri R. Yakovlev, Manfred Bayer, Ilya A. Akimov
Statistical Mechanics · Cross-listed from math-ph
Twisted symmetric exclusion processes and set-theoretical $R$-matrices
Mathieu Dabrowski, Loïc Poulain d'Andecy and Eric Ragoucy
We investigate periodic integrable Markov models, constructed from set-theoretical solutions of the Yang-Baxter equation. We first focus on the simplest class of solutions, called Lyubashenko solutions. We show that the resulting models are equivalent to some twisted Symmetric Simple Exclusion Process (SSEP), which are usual periodic SSEP models where a twist is added on a bond of the ring. We also provide various possible interpretations for these Markov models. Then, we study the long time dynamics of the twisted SSEP, characterising its different stationary states and counting them. Allowing the twist to vary, we examine the possible transitions between the different stationary states. Finally, we extend our construction of Markov models to set-theoretical solutions that are more general than Lyubashenko solutions and show that such models are not equivalent to a twisted SSEP in general.
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Materials Science
A Computational Study of Organic Molecular Crystals for Photocatalytic Water Splitting
James D. Green, Daniel G. Medranda, Hong Wang et al. (+3 more)
Organic crystalline materials are potential candidates for photocatalytic overall water splitting (OWS). Although organic
crystals have been heavily investigated for application in organic electronics, such as organic light-emitting diodes (OLEDs) and
solar cells, there have been comparatively fewer studies into OWS in these materials. A major challenge is the large number of electronic and structural criteria that must be met for a material to make a viable OWS photocatalyst. Optical absorption, reduction and oxidation potentials and charge-transport properties are among the key considerations, and these are influenced both by molecular properties and the solid-state packing arrangement, making computational modelling challenging. Here, we investigate a series of known organic electronic materials that have published
crystal structures using periodic density functional theory (DFT) and compare their calculated electronic properties of optical absorption and reduction and oxidation potentials with literature experimental data. Furthermore we perform a series of gas-phase molecular calculations which show a good agreement with literature data and periodic DFT for the optoelectronic properties of the organic molecular
crystals studied, showing that gas-phase molecular calculations could be used to screen organic
crystals for OWS at a reduced computational cost.
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All authors James D. Green, Daniel G. Medranda, Hong Wang, Andrew I. Cooper, Jenny Nelson, Kim E. Jelfs
Quantum Gases
Correlated phases of moat-band excitons in two dimensions
L. Maisel Licerán, S. H. Boeve and H. T. C. Stoof
We study dilute two-dimensional systems of interacting
excitons with a moat dispersion, whose ground-state
manifold consists of a set of discrete or continuously degenerate energy minima. At low densities and in the presence of contact interactions, it is known that the
bosons can undergo statistical transmutation and give rise to a
chiral spin liquid. Here, we show that long-range interactions such as those expected in excitonic systems introduce a rich competition between the
chiral spin liquid and different kinds of Bose-Einstein condensates. The moat dispersion can favor Bose-Einstein condensation into states occupying multiple momenta, leading to inhomogeneous and supersolid phases with a highly anisotropic superfluid response. We demonstrate that a proper $T$-
matrix renormalization of the
exciton-
exciton interaction is essential for describing these phases and show that they can arise even from purely repulsive interactions. This formalism is employed to obtain the phase diagram of competing homogeneous and stripe condensates with the
chiral spin liquid in an electron-hole
bilayer model. In addition, we show how the $T$
matrix enters the familiar Gross-Pitaevskii framework and map out extended phase diagrams within a pseudopotential approximation. We place our findings in the context of real excitonic systems by discussing the roles of finite lifetimes, disorder, band-structure warping, and nonzero temperatures. We conclude that moat bands can drive Bose-Einstein condensation and supersolidity already at weak coupling, in contrast to the case of a standard
parabolic dispersion.
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Quantum Gases · Cross-listed from physics.atom-ph
Rydberg states with a liquid core
Juan Carlos Acosta Matos, P. Giannakeas and Jan M. Rost
We develop a self-consistent approach that provides an explicit potential for a Rydberg electron whose ionic core consists of a polarizable medium, typically realized with superfluid droplets. The electron's motion remains separable in spherical coordinates, but the radial force exerted by the droplet breaks degeneracy of the angular momentum states non-perturbatively. The ensuing electron spectrum reveals intriguing properties dependent on droplet size and electron excitation. Deviations of the polarizable medium from the continuous spherical distribution can be taken into account as a perturbation of this redefined Rydberg dynamics. We discuss specific but paradigmatic examples for superfluid helium and also propose a way to probe droplet properties including its possible crystallized fraction through stimulated transitions of the Rydberg electron.
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Materials Science
Second-Coordination-Sphere Cation Substitution as a Tool for Controlling Phase Transitions and Performance of the Luminescence Thermometry
Muhammad T. Abbas, M. Szymczak, M. Fandzloch et al. (+3 more)
Despite the exceptionally high relative sensitivities achieved by luminescent thermometers based on first-order structural phase transitions, their principal limitation lies in the inherently narrow thermal operating range associated with the transition temperature. In this work, we demonstrate that partial substitution of Li+ by Na+ ions in the second coordination sphere of Eu3+ ions in LiYO2 enables a substantial shift of the phase transition temperature, thereby allowing controlled optimization of the thermometric performance. This approach represents a significantly more cost-effective and efficient strategy for tuning the phase transition temperature compared with the previously proposed substitution of Y3+ by other lanthanide ions. Importantly, we show that lowering the transition temperature through Na+ incorporation simultaneously introduces static compositional disorder and local
lattice strain. As a consequence, the enthalpy difference between the competing structural phases decreases, and the cooperativity of the
lattice distortion is reduced, indicating a gradual weakening of the first-order character of the phase transition. Our results demonstrate that such structural modifications, while effective in shifting the transition temperature, inevitably lead to a reduction in the relative sensitivity of phase-transition-based luminescent thermometers.
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All authors Muhammad T. Abbas, M. Szymczak, M. Fandzloch, D. Szymanski, A. Sieradzki, L. Marciniak
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
High-quality single photons from cavity-enhanced biexciton-to-exciton transition
Nils Heinisch, Francesco Salusti, Mark R. Hogg et al. (+7 more)
Resonant
laser excitation of a two-level system with subsequent single-
photon emission can be used to generate single
photons with high indistinguishability or Hong-Ou-Mandel (HOM) visibility. However, spectral overlap between excitation
laser and emitted
photons generally poses significant challenges. Furthermore, emitter re-excitation intrinsically limits achievable single-
photon purity. Established solutions mitigate these issues at significant cost to source efficiency and with increased source complexity. This motivates the use of few-level systems with spectral separation of excitation and emission pathways. One option is a three-level cascade. However, without targeted lifetime engineering of emitting states, the cascade naturally limits achievable
photon indistinguishability. Here we study a
semiconductor quantum dot with resonant and selective cavity-enhancement of biexciton-to-
exciton transition. Following resonant two-
photon excitation of the biexciton state, we collect the emitted single
photon with the cavity. This approach circumvents emitter re-excitation and naturally introduces spectral separation of excitation
laser and emitted single
photon. Supported by first experimental results, we demonstrate theoretically that with selective Purcell enhancement, the observed quality quantifiers of single-
photon emission (purity, equivalently $g^{(2)}(0)$, and HOM visibility $\mathcal{V}$, equivalently indistinguishability) are competitive with respect to high-quality deterministic
quantum-dot single-
photon sources. This is already achieved without systematic optimization or targeted system engineering, which firmly places the reported approach as a viable route to the next generation of highest-quality
quantum-dot based deterministic single-
photon sources.
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All authors Nils Heinisch, Francesco Salusti, Mark R. Hogg, Timon L. Baltisberger, Malwina A. Marczak, Sascha R. Valentin, Arne Ludwig, Klaus D. Jöns, Richard J. Warburton, Stefan Schumacher
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Nanoscopy of surface polarization with oblique dipole orientations
V. G. M. Duarte, D. A. Miranda, D. F. P. Cunha et al. (+4 more)
The boundary conditions imposed by confined dipoles with arbitrary orientation on surfaces are presented, extending the conventional in-plane (IP) and out-of-plane (OOP) treatments, here applied for planar and cylindrical sheets. Examples include van der Waals
heterostructures, thin films of molecular aggregates, and metal-dielectric interfaces. For large dipole strengths, the reflectance peak associated with the dipole oscillation frequency splits into two, revealing the presence of oblique dipoles. The loss function for the dipole sheet reveals pairs of polaritonic resonances originating from the IP and OOP dipole components, accessible through near-field probes. The point-dipole model for s-SNOM shows two distinct peaks, revealing higher sensitivity to dipole obliqueness than reflectance experiments. We apply the model to monolayer WSe$_2$, showing that the oblique dipole formulation with a dipole angle of $5.7^\circ$ yields significant improvements in the qualitative and quantitative agreement with an experiment reported in the literature. This work proposes a unified
language for the description of two-dimensional materials, thin films, and interfaces with anisotropic dipolar responses and shows that near-field methods, sensitive to high in-plane momenta, are suitable for measuring such oblique dipoles.
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All authors V. G. M. Duarte, D. A. Miranda, D. F. P. Cunha, M. I. Vasilevskiy, N. Asger Mortensen, A. J. Chaves, N. M. R. Peres
Materials Science · Cross-listed from cs.LG
Stable Long-Horizon Spatiotemporal Prediction on Meshes Using Latent Multiscale Recurrent Graph Neural Networks
Lionel Salesses, Larbi Arbaoui, Tariq Benamara et al. (+2 more)
Accurate long-horizon prediction of spatiotemporal fields on complex geometries is a fundamental challenge in scientific machine learning, with applications such as additive manufacturing where temperature histories govern defect formation and mechanical properties. High-fidelity simulations are accurate but computationally costly, and despite recent advances, machine learning methods remain challenged by long-horizon temperature and gradient prediction. We propose a deep learning framework for predicting full temperature histories directly on meshes, conditioned on geometry and process parameters, while maintaining stability over thousands of time steps and generalizing across heterogeneous geometries. The framework adopts a temporal multiscale architecture composed of two coupled models operating at complementary time scales. Both models rely on a latent recurrent graph neural network to capture spatiotemporal dynamics on meshes, while a variational graph autoencoder provides a compact latent representation that reduces
memory usage and improves training stability. Experiments on simulated powder bed fusion data demonstrate accurate and temporally stable long-horizon predictions across diverse geometries, outperforming existing baseline. Although evaluated in two dimensions, the framework is general and extensible to physics-driven systems with multiscale dynamics and to three-dimensional geometries.
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All authors Lionel Salesses, Larbi Arbaoui, Tariq Benamara, Arnaud Francois, Caroline Sainvitu
Soft Condensed Matter
Analytical response functions for a compressible thin fluid layer with odd viscosity
Abdallah Daddi-Moussa-Ider, Yuto Hosaka and Shigeyuki Komura
Fluids composed of
chiral active components can exhibit odd viscosity, a property that breaks time-reversal and parity
symmetries. We investigate the hydrodynamic response to monopole and dipole singularities in a compressible thin fluid layer with odd viscosity, supported by a conventional lubrication layer. Using the two-dimensional Green's function in
Fourier space, we derive exact analytical solutions for the flow and pressure fields. These solutions provide a detailed description of the hydrodynamic interactions governing the motion of colloidal particles and microswimmers in confined
chiral fluids, offering insight into the role of odd viscosity in modifying particle dynamics and collective behavior. The derived results are directly applicable to modeling transport, control, and self-organization phenomena in active and
chiral microfluidic systems.
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Materials Science
Physical Pictures for Quasisymmetry in Crystals
Bryan D. Assunção, Emmanuel V. C. Lopes, Tome M. Schmidt et al. (+1 more)
Quasisymmetry (QS) provides a novel route to understand and control near-degeneracies, Berry
curvature, optical selection rules, and
symmetry-protected phenomena in
quantum materials. Here we give physical interpretations of the emergence of QS operators across multiple material families. Using density functional theory and the $\mathbf{\mathit{k}}\cdot\mathbf{\mathit{p}}$ formalism, we identify QS subspaces and calculate their representation
matrices, quantifying the quasisymmetry via a metric $\epsilon$ that measures subspace invariance. For Sn/SiC and transition-metal dichalcogenide monolayers, QS corresponds to an emergent mirror
symmetry, whereas in wurtzite
crystals it manifests as an emergent spatial inversion. By contrast, for AgLa the QS appearing in avoided crossings is inherited from a nearby high-
symmetry point rather than being an emergent
lattice symmetry. Combining group-theoretical analysis and $\mathbf{\mathit{k}}\cdot\mathbf{\mathit{p}}$ modeling, our results establish concrete physical pictures for QS and provide practical criteria to diagnose it in first-principles calculations.
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All authors Bryan D. Assunção, Emmanuel V. C. Lopes, Tome M. Schmidt, Gerson J. Ferreira
Superconductivity
Electron-phonon coupling revealed by charge density fluctuations in cuprate superconductors
Martina Fedele, Giacomo Merzoni, Marco Moretti Sala et al. (+6 more)
Electron-
phonon coupling (EPC) governs
lattice dynamics, charge transport, and collective electronic phases in
quantum materials. In several families of unconventional
superconductors, including transition-metal dichalcogenides and kagome metals, growing evidence points to a cooperative role of EPC and dynamic charge-density fluctuations (CDF) in stabilizing superconductivity. However, how the EPC strength evolves across phase diagrams and relates to superconducting properties in strongly correlated systems remains an open question. Here we investigate the interplay between
phonons and the CDF recently identified in cuprate
superconductors. Using resonant inelastic x-ray scattering, we track the dispersion and intensity of bond-stretching
phonons in YBa$_2$Cu$_3$O$_{7-\delta}$ over wide ranges of doping, temperature, and momentum. We find that both the
phonon softening at the CDF wave vector and the EPC strength, extracted from a pronounced
phonon intensity anomaly, are maximized near $p = 0.19$, where superconducting properties are optimal and CDF intensity is strongest. These results identify dynamic charge-density fluctuations, rather than quasi-static charge density waves, as the dominant source of
phonon renormalization in cuprates, and establish a direct correlation between EPC strength and the superconducting dome. More broadly, our measurements highlight EPC as a doping-dependent property of correlated materials, shaped by the electronic environment in which
lattice vibrations are embedded.
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All authors Martina Fedele, Giacomo Merzoni, Marco Moretti Sala, Francesco Rosa, Nicholas B. Brookes, Floriana Lombardi, Sergio Caprara, Giacomo Ghiringhelli, Riccardo Arpaia
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Polariton-polariton coherent coupling in a molecular spin-superconductor chip
Carolina del Río, Marcos Rubín-Osanz, David Rodriguez et al. (+12 more)
The ability to establish coherent communication channels is key for scaling up
quantum devices. Here, we engineer interactions between distant polaritons, hybrid
spin-
photon excitations formed at different lumped-element superconducting resonators within a chip. The chip consists of several resonator pairs, slightly detuned in frequency to make them addressable, capacitively coupled within each pair and inductively coupled to a common readout line. They interact locally with samples of PTMr and Tripak$^{-}$ organic free radicals, deposited onto their inductors, which provide model $S = 1/2$, $g \simeq 2$
spin ensembles. Frequency-dependent microwave transmission experiments, performed at very low temperatures, measure polariton frequencies as a function of
magnetic field in different scenarios. When only one resonator within a pair hosts a molecular sample, the results evidence that
spins couple remotely to the empty LER as well as to the local cavity mode. If both resonators interact with a
spin ensemble, the
magnetic field tunes the polariton frequencies relative to each other, on account of the different
spin-
photon interactions at each LER. When polaritons are brought into mutual resonance, an avoided level crossing emerges that gives direct spectroscopic evidence for a coherent polariton-polariton interaction mediated by the
circuit. Pump-probe experiments reveal that the excitation of a polariton within a connected pair is felt, thus it can be read out, by the other one. These observations, backed by model calculations, illustrate the control and detection of distant
photon-
photon and
spin-
spin correlations and
entanglement in a scalable modular chip.
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All authors Carolina del Río, Marcos Rubín-Osanz, David Rodriguez, Sebastián Roca-Jerat, María Carmen Pallarés, J. Alejandro de Sousa, Paweł Pakulski, José Luis García Palacios, Daniel Granados, Dawid Pinkowicz, Núria Crivillers, Anabel Lostao, David Zueco, Alicia Gomez, Fernando Luis
Statistical Mechanics
A contour for the entanglement negativity of bosonic Gaussian states
Gioele Zambotti and Erik Tonni
We construct a contour function for the logarithmic negativity and the logarithm of the moments of the partial transpose of the reduced density
matrix for multimode bosonic Gaussian states of a free
lattice model. In one spatial dimension, numerical results are obtained for harmonic chains either in the ground state or at finite temperature, by considering, respectively, either a subsystem made by two adjacent or disjoint blocks on the line or a bipartition of the circle. The contour function of the logarithmic negativity diverges only at the entangling points, while the contour function for the logarithm of the moments of the partial transpose is divergent also at the boundary of the bipartite subsystem, as functions of the position. In a two-dimensional conformal field theory, analytic expressions that describe these divergencies are discussed. In one spatial dimension, we explore the partial derivative of the logarithmic negativity of two adjacent intervals with respect to the logarithm of the harmonic ratio of their lengths while their ratio and the other parameters are kept fixed. Considering the ground state of the harmonic chain on the line and in the massive regime, we report numerical results showing that this quantity displays a monotonically decreasing behaviour.
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Statistical Mechanics
A mobility based approach to transport in chiral fluids
Filippo Faedi, Erik Kalz, Ralf Metzler et al. (+1 more)
Chiral fluids, for which the mobility tensor has antisymmetric, off-diagonal components, exhibit transport phenomena absent in conventional systems, including interaction-enhanced
diffusion and negative mobility. While these effects have been predicted theoretically and observed in simulations, their microscopic origin has remained unclear. Here, we address this question using a mobility-based nonequilibrium approach, analysing the steady-state drift of a tracer driven through an interacting
chiral fluid. We show that, under strong chirality, the tracer generates a reversed density wake, in which regions of particle accumulation and depletion are inverted compared to the achiral case. This structural inversion of the wake provides a unified physical mechanism underlying both enhanced
diffusion and negative mobility. Furthermore, we demonstrate that these phenomena are robust to changes in the interaction potential, highlighting their generality as a consequence of odd mobility.
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All authors Filippo Faedi, Erik Kalz, Ralf Metzler, Abhinav Sharma
Strongly Correlated Electrons · Cross-listed from hep-lat
Observation of Robust and Coherent Non-Abelian Hadron Dynamics on Noisy Quantum Processors
Fran Ilčić, Ritajit Majumdar, Emil Mathew et al. (+3 more)
The real-time
evolution of strongly interacting matter remains a frontier of fundamental physics, as classical simulations are hampered by exponential
Hilbert space growth and rapid, unmanageable growth of
quantum entanglement. This study reports the
quantum simulation of
hadron dynamics within a $(1+1)$-dimensional SU(2)
lattice gauge theory using a 156-
qubit IBM superconducting processor. Leveraging a hardware-efficient Loop-String-
Hadron (LSH) encoding, we simulate the dynamics of the physical degrees of freedom on a $60$-site
lattice in the weak-coupling regime, as a crucial step toward the continuum limit. The hardware data reveal confined
meson propagation and early-time oscillations of the mesonic profile, from which we extract a breathing-mode frequency as a spectroscopic observable. Benchmarking against tensor-network simulations of the full LSH
Hamiltonian and Pauli-propagation simulations of the noiseless
circuit supports the validity of the physical approximation, the
quantum algorithm and the observed dynamics within the accessible time window. These results show that physics-native encodings can enable scalable access to coherent non-Abelian real-time dynamics on noisy
quantum hardware.
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All authors Fran Ilčić, Ritajit Majumdar, Emil Mathew, Md. Osama Ali, Nathan Earnest-Noble, Indrakshi Raychowdhury
Mesoscale and Nanoscale Physics
Ultrafast Band-Gap Renormalization in Bilayer Graphene
Eduard Moos, Zhi-Yuan Deng, Hauke Beyer et al. (+6 more)
We demonstrate, by femtosecond time- and angle-resolved photoemission spectroscopy, that photoinduced interlayer charge transfer in a
heterostructure consisting of Bernal-stacked
bilayer graphene and a single atomic layer of silver on 6H-SiC(0001) transiently modulates the intrinsic potential landscape across the silver-
graphene interface. This acts as an ultrafast optoelectronic gate that drives momentum-dependent band renormalizations, resulting in a transient band-gap opening on femtosecond timescales. Simultaneously, the photogenerated hot-carrier population enhances electronic screening, leading to subsequent closing of the band-gap beyond the thermal
equilibrium value. These findings reveal two different mechanisms for photoinduced, reversible control of the electronic band structure in
bilayer graphene – interlayer charge transfer and hot-carrier-enhanced screening – providing a general framework for the ultrafast control of electronic properties in
graphene-based
heterostructures. This opens up novel pathways for the realization of ultrafast optoelectronic devices and the exploration of correlated
quantum phases in
bilayer graphene under non-
equilibrium conditions.
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All authors Eduard Moos, Zhi-Yuan Deng, Hauke Beyer, Arpit Jain, Chengye Dong, Li-Syuan Lu, Joshua A. Robinson, Kai Rossnagel, Michael Bauer
Materials Science
Achieving Robust Extrapolation in Materials Property Prediction via Decoupled Transfer Learning
Tasuku Sugiura and Teruyasu Mizoguchi
Machine learning has revolutionized materials property prediction, yet fails catastrophically when extrapolating beyond training distributions-precisely the capability required for discovering unprecedented materials. Graph neural networks (GNNs) exhibit this collapse because end-to-end training fundamentally couples learned representations to target property distributions, preventing genuine extrapolation. We demonstrate that decoupled transfer learning-separating pretrained GNN feature extractors from simple regressors-overcomes this barrier. Pretrained features provide transferable structural knowledge, while simple regressors enable smooth extrapolation by maintaining learned trends beyond training boundaries. Benchmarked on layered intercalation compounds through four rigorous extrapolation scenarios and a temporal Materials Project split, our framework achieves 68% error reduction (RMSE: 0.881 vs. 2.778 eV/atom) versus end-to-end GNNs for extrapolation. Failure analysis reveals extrapolation succeeds for continuous chemical space but fails for discontinuous space, establishing clear design principles. Validated on
Fermi energy prediction, this framework is immediately deployable using existing pretrained models, requiring no architectural innovations-transforming ML-driven materials discovery.
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Materials Science
Lattice and Orbital-Resolved Fermiology of Metallenes
Kameyab Raza Abidi, Mohammad Bagheri and Pekka Koskinen
Atomically thin metallenes have emerged as a new member of the two-dimensional (2D) materials family. Recent experimental realization of metallenes in the Ångström limit has further intensified interest in this class of 2D materials. However, achieving sub-atomic insight into them demands the most detailed and systematic characterization of their electronic structure. Such understanding is essential for the rational design and exploitation of their properties in plasmonics, catalysis, and
quantum optics. Existing electronic-structure studies are either scattered or focus on a few selected systems, and a comprehensive view of their band structures and
Fermi surfaces remains missing. Here, we address this gap by studying 45 elemental metallenes in six monolayer
lattices (honeycomb, square, hexagonal, and their buckled forms) using density-functional theory. We found that
lattice type primarily fixes the shape and radial placement of the
Fermi-lines, while out-of-plane buckling introduces controlled modifications: it shortens long straight
Fermi-line segments, and occasionally creates, removes, or merges small
Fermi-line pockets. The electronic configuration determines which orbital type dominates the
Fermi level. We summarized Fermiology using a single score for each element, termed pocketness, derived from four descriptors that combine element properties (
symmetry, coordination) with electronic characteristics (dispersion,
Fermi-surface
topology). This score enables targeted angle-resolved photoemission spectroscopy (ARPES) tests, controlled Lifshitz transitions, and provides a predictive basis for transport and device applications.
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Statistical Mechanics · Cross-listed from physics.bio-ph
Decoding cell signaling via optimal transport and information theory
Mintu Nandi and Sosuke Ito
Cellular signal processing performs reliably despite molecular noise. Mutual information (MI) is widely used to quantify signaling fidelity, capturing how well outputs discriminate input states. However, it fails to capture whether the output preserves the statistical structure of the input, a property crucial in morphogen patterning and dose-dependent signaling. To address this gap, we introduce the 2-Wasserstein (2-WD) distance, which provides a
geometric basis for comparing input and output distributions. We define MI as informational fidelity (INF) and the inverse of the 2-WD as
geometric fidelity (GMF). Applying this dual-fidelity framework to canonical regulatory motifs under Gaussian channel approximation reveals
topology-dependent trade-offs: coherent feed-forward loops can perform well in both dimensions, whereas feedback architectures reduce INF to enhance GMF. Experimental analysis of tumor necrosis factor signaling reveals dual-fidelity behavior qualitatively consistent with feedback regulation. RAS-MAPK data analysis further shows that jointly considering INF and GMF better characterizes intracellular signal relay than INF alone. Our results thus indicate that these signaling behaviors are not fully characterized by MI alone; instead, distributional correspondence provides a complementary dimension of signaling fidelity. Our study provides a practical framework for analyzing natural networks and guiding the design of task-specific synthetic
circuits.
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Superconductivity
Extended Mean-Field Theory for the 2D Hubbard Model in Degenerate Dilute Electron Gases: Fluctuations, Superconducting Dome, and Interaction Mechanisms in Strontium Titanate
Xing Yang, Xinyu Zhang and Xuchang Zhang
Strontium titanate ($\mathrm{SrTiO_3, STO}$) dome-shaped superconducting transition temperature as a function of chemical potential, consistent with STO experiments, and shows that tunable s-wave and d-wave
symmetries are modulated by doping. Superconducting fluctuations validate the mean-field approximation at low temperatures but destroy pairing at higher temperatures. The charge-density-wave order competes with superconductivity, enhances the effective electron mass inversely with the chemical potential, and increases with the interaction strength $U$ and the temperature $T$. SDW order is rare and fragile, while an additional
magnetic term induces subtle band splitting. These findings suggest e-e contributions to STO's transport anomalies and provide criteria to distinguish e-e from e-ph origins, offering insights for engineering higher $T_c$ in dilute systems.
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Materials Science
Irradiation-Driven Recrystallization in Fusion-Grade Tungsten: A Mesoscale, Microstructure-Aware Model
Jinxin Yu, Sicong He, Giacomo Po et al. (+3 more)
Tungsten (W) is the leading candidate material for
plasma-facing components in fusion reactors, yet its upper operational temperature is limited by premature grain growth and recrystallization processes. Irradiation adds further complications by generating defect clusters and transmutation products that alter both the driving forces and kinetics of grain boundary motion. In this work, we develop a physics-based, multiscale framework that couples
crystal plasticity,
stochastic cluster dynamics, and discrete grain boundary dynamics to model the co-
evolution of plastic deformation, irradiation damage, and grain growth in fusion-grade tungsten polycrystals. The approach enables simulations on realistic microstructures with arbitrary grain size and misorientation distributions, without recourse to mean-field simplifications. The model captures (i) the spatial heterogeneity of dislocation density distribution during hot working; (ii) irradiation-induced defect accumulation under fusion conditions, and (iii) the buildup of chemical and elastic driving forces for grain boundary migration and microstructural
evolution. Parametric studies demonstrate the dominant influence that temperature has on thermally activated grain-boundary mobility, a weaker dependence on prior strain, and a pronounced retardation of recrystallization by rhenium segregation arising from
neutron transmutation. Under fusion energy irradiation conditions, our framework predicts a substantial reduction of the effective recrystallization temperature relative to unirradiated microstructures, while Re production restores and even elevates this limit. By providing quantitative projections of recrystallization kinetics and in-service recrystallization temperatures, this work establishes a predictive tool for assessing the lifetime and operational envelope of W-based
plasma-facing materials under fusion conditions.
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All authors Jinxin Yu, Sicong He, Giacomo Po, Jason R. Trelewicz, Timothy J. Rupert, Jaime Marian
Materials Science · Cross-listed from physics.optics
Dynamic topological exciton-polaritons enabling ultrafast logic operations
Feng Jin, Hao Zheng, Zhe Zhang et al. (+7 more)
Topological active materials have emerged as powerful paradigm bridging the discovery of exotic topological phases of matter with the development of functional topological devices. The recent extension of these material systems into dynamic regime, where topological properties can be actively manipulated at ultrafast timescales, promises unprecedented control over topological states and their functionalities. However, translating the static topological lasing signals into high-performance logic functions remain highly challenging, which imposes a far more stringent set of materials attributes. Here, leveraging the strong nonlinearity and pronounced spectral isolation of perovskite
exciton-polaritons embedded in a Dirac
vortex microcavity, we experimentally demonstrate the dynamic topological Majorana-like state polariton condensation with its ultrafast logic operations at room temperature. By actively coordinating pump and control beams in both spectral and temporal domain, we dynamically steer the topological polariton condensation process and demonstrate AND and NOT logic operations, achieving record extinction ratio (~20 dB), extremely low control fluence (~0.2 nJ/cm2) and sub-picosecond response time (~500 fs). Our results expand the frontier of dynamic
topology and establish a novel pathway towards robust, ultrafast, and reconfigurable on-chip polaritonic logic
circuits.
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All authors Feng Jin, Hao Zheng, Zhe Zhang, Jiaohao Ren, Yuxi Liu, Qing Zhang, Daniele Sanvitto, Timothy C. H. Liew, Baile Zhang, Rui Su
Mesoscale and Nanoscale Physics
Method for real-time monitoring of paramagnetic reactions using spin relaxometry with fluorescent nanodiamonds
Trent Ralph, Erin S. Grant, Lianne Lay et al. (+2 more)
Spin relaxometry using fluorescent nanodiamonds (FNDs) has been applied successfully to sense numerous paramagnetic target molecules such as free radicals and metalloproteins. However, despite their high sensitivity, T1
spin relaxation measurements are often hampered by their slow acquisition speed. Here, we demonstrate a method that allows for real-time monitoring of paramagnetic chemical reactions. We demonstrate T1
spin relaxometry from thousands of FNDs using an optimised cuvette-based system integrating an avalanche photodiode operated in linear mode, and a fast, fieldprogrammable gate array (FPGA) for data collation. We demonstrate chemical monitoring of the reduction of Cu(II) to Cu(I) ions in-solution with a 15 second integration using an optimised T1 sensing protocol. Our method achieves more than two orders of magnitude speed up with an order of magnitude reduction in cost when compared with traditional techniques. With further technical improvements, we believe this in-solution method could be extended to sense the sub-second chemical kinetics of paramagnetic molecules in solution.
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All authors Trent Ralph, Erin S. Grant, Lianne Lay, Sepehr Ahmadi, David A. Simpson
Strongly Correlated Electrons
Optical and Hall conductivity of the two dimensional Hubbard model: effective theory description, sign-problem-free Monte Carlo simulation and applications to the cuprate superconductors
Xinyue Liu and Tao Li
Exact formulas for the optical conductivity and the
Hall conductivity of the two dimensional Hubbard model are derived in terms of an effective theory description of the local moment fluctuation in the system. In this framework, the
quantum Monte Carlo simulation of the electromagnetic response of such a strongly correlated electron system becomes sign-problem-free in many physically relevant cases. In particular, it is sign-problem-free when we assume the widely used Millis-Monien-Pines form for the phenomenological susceptibility in the effective action of the fluctuating local moment, even though these local moments are now subjected to Landau damping as a result of their coupling to the itinerant quasiparticle on the
fermi surface. This is true more generally when a $\varphi^{4}$ term is included in the effective action and is thus not restricted to the Gaussian limit. Here we demonstrate the power of this framework by studying the effect of thermal fluctuation of the local moment on the optical conductivity $\sigma^{xx}(\omega)$ and the
Hall conductivity $\sigma^{xy}(\omega)$ of the cuprate
superconductors. Both $\sigma^{xx}(\omega)$ and $\sigma^{xy}(\omega)$ calculated are found to exhibit a two-component structure, with a Drude component at low energy and a mid-infrared component at higher energy. Depending on the relative importance of the hole pocket and the electron pocket on the reconstructed
fermi surface and the coupling strength to the local moment, the Drude component in $\mathrm{Im}\sigma^{xy}(\omega)$ can be either positive or negative.(full-length abstract can be found in the main text.)
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Materials Science
Efficient photocatalytic CO2 Reduction to C2+ Products with Pt1-xPdxSn4 Dirac Nodal Arc Semimetal
Kangwang Wang, Jie Zhan, Jun Liu et al. (+6 more)
The photochemical CO2 reduction reaction represents a zero-carbon pathway for converting CO2 into value-added chemicals, yet its industrial implementation has been constrained by low selectivity and product diversity. Dirac nodal arc semimetals characterized by ultrahigh carrier mobility with over 25000 cm2 V-1 s-1 offer a promising platform to search for efficient catalysts for CO2 conversion. Herein, we demonstrate that strategic Pt incorporation into PdSn4 optimizes the electronic structure and carrier dynamics of this Dirac semimetal. Experimental and theoretical analyses reveal that the resulting Pd-Sn-Pt local electronic structure redistributes charge density around Pd and Pt atoms, which facilitates C-C coupling via *OC-COH and *OC-CHOH intermediates and enhances carrier mobility by 40% versus the pristine PdSn4 single
crystal. The optimized Pd0.4Pt0.6Sn4 single
crystal achieves C2H4 with formation rate of 0.000328 mol g-1 h-1, product selectivity of 73.1% and electron-based selectivity of 89%. This work establishes electronic-structure-tunable Dirac semimetals as a new paradigm for multi-carbon photochemical CO2 reduction, providing a design strategy for next-generation photocatalysts.
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All authors Kangwang Wang, Jie Zhan, Jun Liu, Zaichen Xiang, Wanyi Zhang, Lingyong Zeng, Kai Yan, Yan Sun, Huixia Luo
Quantum Gases · Cross-listed from hep-th
Simulating Quantum Field Theories with Boundaries in Curved Spacetimes Using Open Spin Systems
Shunichiro Kinoshita, Keiju Murata, Daisuke Yamamoto et al. (+1 more)
We develop a framework to simulate
quantum field theories (QFTs) with boundaries in $(1+1)$-dimenmsional curved spacetimes by employing open
spin systems. Building upon our previous work that established a mapping from
spin systems to QFTs in periodic geometries, we extend the correspondence to systems with boundaries, where boundary conditions play a crucial role in shaping the dynamics. Focusing on Majorana
fermions, we derive the allowed boundary conditions from the requirement of inner product conservation and formulate their realization in
spin systems. The corresponding
spin model is shown to reproduce boundary conditions of QFT accurately when a free function in the
spin model is appropriately chosen. As an explicit demonstration, we analyze a flat spacetime example, comparing spectra, mode functions, and linear responses between the continuum and
lattice descriptions. Our findings confirm that open
spin systems can successfully replicate QFT dynamics with boundaries.
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All authors Shunichiro Kinoshita, Keiju Murata, Daisuke Yamamoto, Ryosuke Yoshii
Strongly Correlated Electrons
Observation of Room-temperature Charge Density Wave Correlations via Coherent Phonon Spectroscopy in Sn-doped Kagome Superconductor CsV$_3$Sb$_5$
Qinwen Deng, Andrea Capa Salinas, Suchismita Sarker et al. (+3 more)
In this work, we perform ultrafast time-resolved reflectivity measurements to track the
evolution of charge density wave (CDW) correlations in Sn-doped Kagome
superconductor CsV$_3$Sb$_{5-x}$Sn$_x$. By extracting the coherent
phonon spectrum, we evidence robust signatures of CDW correlations at temperature and doping ranges far beyond the phase boundary of long-range CDW order. Remarkably, we unveil short-range CDW correlations survive up to room temperature in $x = 0.32$ Sn-doped CsV$_3$Sb$_5$, supported by synchrotron X-ray diffraction measurements. We point out the introduction of quenched disorder by Sn doping can pin the CDW and form static short-range CDW, which can explain the observed persistent CDW signatures. Our results thus corroborate the ubiquity and robustness of CDW correlations in Sn-doped CsV$_3$Sb$_5$ and provide new insights on the role of disorders on the CDW correlations in AV$_3$Sb$_5$ family.
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All authors Qinwen Deng, Andrea Capa Salinas, Suchismita Sarker, Leon Balents, Stephen D. Wilson, Liang Wu