Strongly Correlated Electrons
Dimensionality-Changing Transition from a Non-Fermi Liquid to a Spin-Solid in a Multichannel Kondo Lattice
Simon Martin, Marcin Raczkowski, Fakher F. Assaad et al. (+1 more)
A multichannel Kondo system, where a single
quantum spin couples to multiple channels of an electronic bath, provides one of the simplest examples of a zero-dimensional non-
Fermi liquid. It is natural to ask: what happens when an extensive number of such systems are coupled together? A simple renormalization group argument implies that in a chain of SU(N) multichannel
quantum systems, where each
spin is coupled to its own bath of K channels, the individual
spins dynamically decouple at low energy when N>K, resulting in a 'sliding' non-
Fermi liquid. Using
Quantum Monte Carlo (QMC) simulations, we find evidences of a continuous, 'dimensionality-changing' phase transition out of this non-
Fermi liquid into a valence-bond solid phase as the intersite coupling is increased. Remarkably, at the critical point, correlations exhibit a power-law behavior even along the direction in which the
spins are coupled, indicating the breakdown of dynamical decoupling at the transition. We also develop an RG scheme to understand the universal aspects of this transition.
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All authors Simon Martin, Marcin Raczkowski, Fakher F. Assaad, Tarun Grover
Soft Condensed Matter
Coupled imbibition and evaporation of droplets deposited on a nanoporous layer
Joachim Trosseille, Hugo Bellezza and Olivier Vincent
Liquids in nanoscale hydrophilic pores generate capillary pressures so large that they could theoretically climb kilometers against
gravity. However, droplets on thin nanoporous layers form imbibition fronts stopping at millimeters or less due to evaporation competing with capillary flow. Such droplet infiltration dynamics is of growing interest for studying confined fluids and for applications such as water harvesting, printing, chemical delivery, actuation, and sensing. Here, we investigate theoretically and experimentally the spontaneous imbibition and evaporation of sessile droplets into thin mesoporous layers, focusing on their dependence on imposed relative humidity (RH). Theoretically, we provide a unified analytical approach for the dynamics of the wetted annulus ("
halo") around the droplet, accounting for arbitrary
halo dimensions and confinement-induced thermodynamic shifts (Kelvin effect). Experimentally, we study water droplets on oxidized porous silicon layers (pore diameter 3-4 nm, thickness 5 $\mu$m), systematically investigating how
halo and droplet dynamics depend on RH. We show that
halo formation timescales diverge at a critical RH due to the Kelvin effect, as illustrated by comparing RH-dependent evaporation rates in the
halo (confined
liquid) and in the droplet (bulk
liquid). Our analysis also reveals an apparent divergence of the imbibition coefficient, unexplained by standard capillary models, suggesting a key role for Kelvin-driven vapor transport along the porous surface. The complex couplings revealed by our study call for caution in interpreting
halo dynamics data. Our results also highlight RH as a powerful control parameter for tuning droplet imbibition behavior and infiltration patterns.
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Other Condensed Matter · Cross-listed from quant-ph
Mind the gaps: The fraught road to quantum advantage
Jens Eisert and John Preskill
Quantum computing is advancing rapidly, yet substantial gaps separate today's noisy intermediate-scale
quantum (NISQ) devices from tomorrow's fault-tolerant application-scale
quantum (FASQ) machines. We identify four related hurdles along the road ahead: (i) from error mitigation to active error detection and correction, (ii) from rudimentary error correction to scalable fault tolerance, (iii) from early heuristics to mature, verifiable
algorithms, and (iv) from exploratory simulators to credible advantage in
quantum simulation. Targeting these transitions will accelerate progress toward broadly useful
quantum computing.
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Mesoscale and Nanoscale Physics · Cross-listed from hep-ph
Beyond Qubits: Multilevel Quantum Sensing for Dark Matter
Xiaolin Ma, Volodymyr Takhistov, Norikazu Mizuochi et al. (+1 more)
Quantum sensing with
qubits has advanced fundamental physics searches, but higher dimensional systems offer untapped potential. We present a universal qutrit framework that yields a sequence-independent fourfold increase in
quantum Fisher information and a twofold gain in sensitivity. In ultralight dark matter searches,
spin-1 NV-center qutrits can enhance the
axion-electron coupling reach by an order of magnitude beyond
qubits. This principle applies broadly to multilevel
quantum systems including superconducting, neutral atom and trapped-ion qutrits, establishing higher dimensional sensing as a powerful tool for probing new physics.
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All authors Xiaolin Ma, Volodymyr Takhistov, Norikazu Mizuochi, Ernst David Herbschleb
Strongly Correlated Electrons · Cross-listed from physics.chem-ph
Fokker-Planck equation governing the distribution of walkers in AFQMC
Alfred Li, Ankit Mahajan and Sandeep Sharma
Auxiliary-field
quantum Monte Carlo (AFQMC) is typically formulated as an open-ended random walk in an overcomplete space of Slater determinants, implemented through a Langevin equation. However, the explicit form of the underlying Fokker-Planck equation governing the walker population distribution has remained unknown. In this paper, we derive the Fokker-Planck equation for AFQMC and propose a novel numerical scheme to solve it. The solution of the Fokker-Planck equation reveals the wavefunction actually sampled by the AFQMC
algorithm. Interestingly, we find that even when the exact ground state is used as a guiding wavefunction in constrained path AFQMC, contrary to the common assumption, the wavefunction sampled by AFQMC is not exact. Beyond clarifying several fundamental aspects of AFQMC, the availability of a Fokker-Planck equation formulation opens new avenues for systematically improving its accuracy, which we outline in this paper.
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Strongly Correlated Electrons
Cesar A. Gallegos, Rafael M. Magaldi, Andrew Millis et al. (+1 more)
We investigate the weak interaction integer
quantum Hall (IQH) phase, the intermediate interaction phase identified as a
chiral spin liquid (CSL) and the transition between them in the triangular
lattice Hofstadter-Hubbard model at a density of one electron per site in an orbital
magnetic field corresponding to one-quarter flux per plaquette. Our primary tool is the finite system density
matrix renormalization group (DMRG) method with both interaction-strength scan and fixed interaction techniques for cylinders of circumference 3, 5, and 7 and lengths up to 240. For the IQH phase, we use single particle exact diagonalization to clarify finite size effects, including an excess charge on the edges of our cylinders, and the limitations of
entanglement spectra degeneracies on small circumference cylinders. For both phases, we use DMRG to study the
entanglement spectra, the
entanglement entropy, and the effect of flux insertion on charge and
spin pumping, all of which show key differences between the two phases. To study the transition, we use interaction-strength scans extending between the two phases, and apply a scaling data collapse of a bond-dimerization order parameter to extract critical exponents. We also extract critical behavior from the divergence of correlation lengths on the IQH side, measuring decay away from edges of both the dimerization order parameter and transverse edge currents. The critical behavior and exponents are consistent with an Ising transition in 1+1 dimensions. Finally, we obtain excited states in various
quantum number sectors finding that the gap to a charge neutral momentum $\pi$ excitation corresponding to fluctuations of the dimerization order parameter closes in the vicinity of the critical point but gaps to other excitations remain large.
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All authors Cesar A. Gallegos, Rafael M. Magaldi, Andrew Millis, Steven R. White
Strongly Correlated Electrons
Temperley-Lieb integrable models and fusion categories
Matthew Blakeney, Luke Corcoran, Marius de Leeuw et al. (+2 more)
We show that every fusion category containing a non-invertible, self-dual object $a$ gives rise to an integrable anyonic chain whose
Hamiltonian density satisfies the Temperley-Lieb
algebra. This
spin chain arises by considering the projection onto the identity channel in the fusion process $a\otimes a$. We relate these models to Pasquier's construction of ADE
lattice models. We then exploit the underlying Temperley-Lieb structure to discuss the spectrum of these models and argue that these models are gapped when the
quantum dimension of $a$ is greater than 2. We show that for fusion categories where the dimension is close to 2, such as the Fib$\times$Fib and Haagerup fusion categories, the finite size effects are large and they can obscure the numerical analysis of the gap.
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All authors Matthew Blakeney, Luke Corcoran, Marius de Leeuw, Balazs Pozsgay, Eric Vernier
Materials Science
A unified picture of phonon anomalies in crystals and glasses
Alessio Zaccone
Phonon spectra in solids often display anomalies that defy the simple Debye law, most prominently the van Hove singularity in
crystals and the
boson peak in glasses. Although traditionally regarded as distinct, both features are increasingly recognized as sharing a common physical origin. In a recent work, G. Ding et al. (Nat. Phys. 2025) propose a resonant-damping model that unifies these anomalies within a single framework. By coupling
phonon damping to vibrational softening, their theory explains why some materials exhibit van Hove peaks, others
boson peaks, and many show both. This advance extends earlier ideas and theories of Baggioli and Zaccone on the competition between
phonon propagation and damping, while also connecting to microscopic mechanisms such as nonaffine motions in glasses. The resonant-damping paradigm thus offers a promising step toward a unified understanding of vibrational anomalies across ordered and disordered solids.
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Strongly Correlated Electrons
Canted antiferromagnetism and excitonic order in gated double-layer graphene
V. Apinyan and T. K. Kopeć
We study the effects of the electron-electron interactions on the excitonic properties and charge-density modulations in the AB stacked double-layer (DL)
graphene, placed in the external gate-potential $V$. The coexistence of the canted
antiferromagnetic order and excitonic pairing gap has been studied with the help of the generalized Hubbard model. We calculate the chemical potential $\mu$, the average charge density difference between the layers $\delta{\bar{n}}$, the
antiferromagnetic gap-function $\Delta_{\rm AFM}$ and the excitonic order parameters $\Delta_{\sigma}$ in the zero temperature limit. We found that the excitonic pairing order parameter has a larger energy scale than the canted
antiferromagnetic gap-function. The charge neutrality, in the DL
graphene system, occurs only in the absence of the external gate-potential $V$. Moreover, we have shown that the values of the
antiferromagnetic gap-function $\Delta_{\rm AFM}$ and excitonic order parameter $\Delta_{\sigma}$ are always increasing at the large values of inter-layer Coulomb interaction, while they are decreasing for large values of the applied gate-potential $V$.
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Strongly Correlated Electrons
Excitonic correlations in the system of gated metallic wires with the applied Zeeman magnetic field
V. Apinyan and T. Kopeć
We have studied the electron-electron interactions in the system composed of two metallic wires, placed in the external
magnetic and electric fields. The interactions between the electrons in the wires have been taken into account within the usual Hubbard model. We have considered both half-filling and partial-filling limits for the occupation of the atomic
lattice sites. We show the existence of the excitonic pairing in this low-dimensional system and calculate the excitonic order parameter in different electron-electron interaction regime,
magnetic field and temperature. We demonstrate that the usual Hubbard-$U$ interaction leads to strong electron localization which enhance the local
antiferromagnetic order in the system.
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Strongly Correlated Electrons
Krylov space dynamics of ergodic and dynamically frozen Floquet systems
Luke Staszewski, Asmi Haldar, Pieter W. Claeys et al. (+1 more)
In isolated
quantum many-body systems periodically driven in time, the asymptotic dynamics at late times can exhibit distinct behavior such as thermalization or dynamical freezing. Understanding the properties of and the convergence towards infinite-time (nonequilibrium) steady states however remains a challenging endeavor. We propose a physically motivated Krylov space perspective on Floquet thermalization which offers a natural framework to study rates of convergence towards steady states and, simultaneously, an efficient numerical
algorithm to evaluate infinite-time averages of observables within the diagonal ensemble. The effectiveness of our
algorithm is demonstrated by applying it to the periodically driven mixed-field Ising model, reaching system sizes of up to 30
spins. Our method successfully resolves the transition between the ergodic and dynamically frozen phases and provides insight into the nature of the Floquet eigenstates across the phase diagram. Furthermore, we show that the long-time behavior is encoded within the localization properties of the Ritz vectors under the Floquet
evolution, providing an accurate diagnostic of ergodicity.
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All authors Luke Staszewski, Asmi Haldar, Pieter W. Claeys, Alexander Wietek
Quantum Gases · Cross-listed from quant-ph
Atomic-superfluid heat engines controlled by twisted light
Aritra Ghosh, Nilamoni Daloi and M. Bhattacharya
We theoretically propose a
quantum heat engine using a setup consisting of a ring-trapped Bose-Einstein condensate placed in a Fabry-Pérot cavity where the optical field carries orbital angular momentum. We first show that the cavity-enhanced light-atom coupling leads to the emergence of polaritonic modes whose character can be reversibly switched between photonlike and phononlike by detuning sweeps, allowing work extraction governed by distinct reservoirs. We investigate the dependence of the engine efficiency on the orbital angular momentum. Beyond ideality, we discuss finite-time scenarios based on shortcuts to adiabaticity such that the efficiency retains its ideal-operation value, despite finite-time operation. Our analysis identifies orbital angular momentum as a control knob that can reconfigure the performance of such
quantum heat engines.
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Quantum Gases · Cross-listed from physics.atom-ph
Single Sr Atoms in Optical Tweezer Arrays for Quantum Simulation
Veronica Giardini, Luca Guariento, Andrea Fantini et al. (+6 more)
We report on the realization of a platform for trapping and manipulating individual $^{88}$Sr atoms in optical tweezers. A first cooling stage based on a blue shielded magneto-optical trap (MOT) operating on the $^1S_0$ -> $^1P_1$ transition at 461 nm enables us to trap approximately $4\times 10^6$ atoms at a temperature of 6.8 mK. Further cooling is achieved in a narrow-line red MOT using the $^1S_0$ -> $^3P_1$ intercombination transition at 689 nm, bringing $4\times 10^5$ atoms down to 5 $\mu$K and reaching a density of $\approx 10^{10}$ cm$^{-3}$. Atoms are then loaded into 813 nm tweezer arrays generated by crossed acousto-optic deflectors and tightly focused onto the atoms with a high-numerical-aperture objective. Through light-assisted collision processes we achieve the collisional blockade, which leads to single-atom occupancy with a probability of about $50\%$. The trapped atoms are detected via fluorescence imaging with a fidelity of $99.986(6)\%$, while maintaining a survival probability of $97(2)\%$. The release-and-recapture measurement provides a temperature of $12.92(5)$ $\mu$K for the atoms in the tweezers, and the ultra-high-
vacuum environment ensures a
vacuum lifetime higher than 7 min. These results demonstrate a robust alkaline-earth tweezer platform that combines efficient loading, cooling, and high-fidelity detection, providing the essential building blocks for scalable
quantum simulation and
quantum information processing with Sr atoms.
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All authors Veronica Giardini, Luca Guariento, Andrea Fantini, Shawn Storm, Massimo Inguscio, Jacopo Catani, Giacomo Cappellini, Vladislav Gavryusev, Leonardo Fallani
Materials Science
Hexa-Graphyne: A Transparent and Semimetallic 2D Carbon Allotrope with Distinct Optical Properties
Jhionathan de Lima and Cristiano Francisco Woellner
Herein, we conduct a comprehensive investigation of Hexa-graphyne (HXGY), a planar carbon allotrope formed by distorted hexagonal and rectangular rings incorporating sp and sp$^2$-hybridized carbon atoms. First-principles calculations confirm its energetic, dynamical and thermal stability (up to at least 1000 K). Regarding its band structure, this material exhibits a semimetallic nature. It exhibits high mechanical compliance, with a Young's modulus approximately 13 times lower and a Poisson's ratio nearly 4 times higher than those of
graphene. The optical response is marked by strong ultraviolet absorption, high infrared reflectivity, and pronounced transparency in the visible-light range. Raman and infrared spectra exhibit sharp and well-separated peaks, providing a clear signature of acetylenic linkage stretching vibrations. Nanoribbon structures derived from HXGY show distinct electronic behaviors depending on the edge termination type and width. These findings highlight the HXGY potential for nanoelectronic and optoelectronic applications.
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Superconductivity
Soft Mode Origin of Charge Ordering in Superconducting Kagome CsV$_3$Sb$_5$
Philippa Helen McGuinness, Fabian Henssler, Manex Alkorta et al. (+12 more)
Charge-density-wave (CDW) order and superconductivity coexist in the kagome metals AV$_3$Sb$_5$ (A=K, Cs, Rb), raising fundamental questions about the mechanisms driving their intertwined phases. Here we combine high-resolution inelastic X-ray scattering with first-principles calculations to uncover the origin of CDW formation in CsV$_3$Sb$_5$. Guided by structure factor analysis, we identify a soft
phonon mode along the reciprocal M-L direction, with the strongest effect at the L point, where the elastic scattering intensity also grows most rapidly upon cooling. First-principles calculations incorporating
lattice anharmonicity and electron-
phonon coupling reproduce these observations and establish a soft-mode instability at the L point as the driving mechanism of CDW formation. Despite the weakly first-order character of the transition, our results unambiguously demonstrate that the CDW in CsV$_3$Sb$_5$ originates from a softened
phonon, clarifying its microscopic origin and highlighting the central role of
lattice dynamics in kagome metals.
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All authors Philippa Helen McGuinness, Fabian Henssler, Manex Alkorta, Mark Joachim Graf von Westarp, Artem Korshunov, Alexei Bosak, Daisuke Ishikawa, Alfred Q. R. Baron, Michael Merz, Amir-Abbas Haghighirad, Maia G. Vergniory, Sofia-Michaela Souliou, Rolf Heid, Ion Errea, Matthieu Le Tacon
Quantum Gases
Extracting transport coefficients from local ground-state currents
Felix A. Palm, Alexander Impertro, Monika Aidelsburger et al. (+1 more)
Transport properties are central to characterizing
quantum matter, yet their extraction typically requires external forcing and time-resolved measurements. In this work, we propose a scheme to access transport coefficients directly from measurements of local static ground-state currents – quantities readily accessible in
quantum-engineered platforms. By exploiting the exponential decay of correlations in gapped systems and the finite velocity of correlation spreading, we demonstrate that the local
Hall response of correlated
insulators can be reconstructed from a small set of quasi-local current observables. We derive explicit relations connecting these static observables to a practical local Chern marker, and introduce a scalable digital protocol for measuring the required generalized currents in
quantum simulators. We demonstrate the applicability of our approach through numerical studies of emblematic Chern-
insulator systems, both in the non-interacting and strongly-correlated (fractional) regime. Our method extends naturally to a broad class of correlated systems, even at finite temperature, offering a broadly applicable route to probing transport in engineered
quantum matter.
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All authors Felix A. Palm, Alexander Impertro, Monika Aidelsburger, Nathan Goldman
Soft Condensed Matter
Flexel ecosystem: simulating mechanical systems from entities with arbitrarily complex mechanical responses
Paul Ducarme, Bart Weber, Martin van Hecke et al. (+1 more)
Nonlinearities and instabilities in mechanical structures have shown great promise for
embedding advanced functionalities. However, simulating structures subject to nonlinearities can be challenging due to the complexity of their behavior, such as large shape changes, effect of pre-tension, negative stiffness and instabilities. While traditional finite element analysis is capable of simulating a specific nonlinear structure quantitatively, it can be costly and cumbersome to use due to the high number of degrees of freedom involved. We propose a framework to facilitate the exploration of highly nonlinear structures under quasistatic conditions. In our framework, models are simplified by introducing `flexels', elements capable of intrinsically representing the complex mechanical responses of compound structures. By extending the concept of nonlinear springs, flexels can be characterized by multi-valued response curves, and model various mechanical deformations, interactions and stimuli, e.g., stretching, bending, contact, pneumatic actuation, and cable-driven actuation. We demonstrate that the versatility of the formulation allows to model and simulate, with just a few elements, complex mechanical systems such as pre-stressed tensegrities, tape spring mechanisms, interaction of buckled beams and pneumatic soft gripper actuated using a metafluid. With the implementation of the framework in an easy-to-use Python library, we believe that the flexel formulation will provide a useful modeling approach for understanding and designing nonlinear mechanical structures.
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All authors Paul Ducarme, Bart Weber, Martin van Hecke, Johannes T.B. Overvelde
Mesoscale and Nanoscale Physics
Two parameter scaling of conductance in quantum Hall effect
Yurii G. Arapov, Svetlana V. Gudina, Vladimir N. Neverov et al. (+2 more)
After a brief survey of theoretical concepts for the two-parameter scaling theory in the integer
quantum Hall effect regime, a comprehensive set of early, recent and new experimental results on constructing scaling diagrams for conductance in 2D
semiconductor structures, as well as in
graphene is displayed. A comparative analysis of scaling diagrams obtained from experimental data with calculated ones is carried out.
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All authors Yurii G. Arapov, Svetlana V. Gudina, Vladimir N. Neverov, Nikita S. Sandakov, Nina G. Shelushinina
Materials Science
Accelerating Moment Tensor Potentials through Post-Training Pruning
Zijian Meng, Karim Zongo, Matthew Thoms et al. (+2 more)
Moment Tensor Potentials (MTPs) are machine-learning interatomic potentials whose basis functions are typically selected using a level-based scheme that is data-agnostic. We introduce a post-training, cost-aware
pruning strategy that removes expensive basis functions with minimal loss of accuracy. Applied to nickel and silicon-oxygen systems, it yields models up to seven times faster than standard MTPs. The method requires no new data and remains fully compatible with current MTP implementations.
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All authors Zijian Meng, Karim Zongo, Matthew Thoms, Ryan Eric Grant, Laurent Karim Béland
Superconductivity
Point-contact Andreev reflection spectroscopy of layered superconductors with device-integrated diamond anvil cells
Che-hsuan Ku, Omargeldi Atanov, King Yau Yip et al. (+9 more)
Superconductors that can be mechanically exfoliated are an interesting platform for exploring superconducting properties tuned by layer thickness. These layered
superconductors are also expected to exhibit sensitivity to applied pressure. While pressure has been demonstrated to be an effective way of tuning bulk
superconductors, analogous studies on superconducting thin flakes have been limited due to technical challenges. In particular, spectroscopic measurements under pressure remain insufficiently explored. In this work, we functionalized the diamond anvil
cell technique for point-contact Andreev reflection spectroscopy (PCAR) measurement on thin-flake materials under pressure, offering the opportunity to obtain spectroscopic information on superconductivity. To validate the feasibility of this method, we have conducted PCAR measurements on iron-selenide thin flakes to extract temperature-dependent superconducting gap values under ambient and high pressure. Combine with the proven magnetotransport capability, our method provides a conceptually simple tool for a detailed examination of thin-flake
superconductors under pressure.
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All authors Che-hsuan Ku, Omargeldi Atanov, King Yau Yip, Wenyan Wang, Siu Tung Lam, Jiayu Zeng, Wei Zhang, Zheyu Wang, Lingfei Wang, Tsz Fung Poon, Rolf Lortz, Swee K. Goh
Materials Science
Unraveling the defect landscape of wide-bandgap perovskites from electrical and photoelectrical characterization of thin films and solar cells
L. Kopprio, J. Caram, S. Le Gall et al. (+7 more)
Understanding and controlling defect states in halide perovskites is critical to advancing their performance in
solar cells, yet their complex defect landscape remains elusive. Charged defects in perovskites can migrate under an applied electric field, complicating their characterization by conventional approaches. Here, we integrate current-voltage (IV) and thermal admittance spectroscopy (TAS) with lateral photocurrent methods, including thermal steady-state photocurrent (SSPC) and steady-state photocarrier grating (SSPG), to probe the kinetic and electrical properties of defects in thin films of
vacuum-deposited FA$_{0.7}$Cs$_{0.3}$Pb(I$_{0.9}$Br$_{0.1}$)$_3$ perovskite. The experimental results are interpreted with advanced numerical simulations to account not only for the energy positions of defects in the bandgap but also for their mobilities. The low activation energies observed in the capacitance steps rule out free-carrier trapping and emission as their origin, pointing instead to charged-defect (or ionic) migration. We estimate the free-carrier mobilities and the defect distribution inside the bandgap, along with their capture coefficients. Our results reveal exponential bandtail states arising from dynamic
lattice disorder and identify a Gaussian-like defect distribution 0.21~eV from the band edge, which dominates recombination. Donors and acceptors are present at nearly equal concentrations ($\sim 2 \times 10^{18}$~cm$^{-3}$). The mobile species responsible for the capacitance steps is one of the dopants, exhibiting an average mobility of $10^{-8}$~cm$^2$~V$^{-1}$~s$^{-1}$ at 300~K with a thermal activation energy of around 0.34~eV.
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All authors L. Kopprio, J. Caram, S. Le Gall, F. Ventosinos, L. Gil-Escrig, H. J. Bolink, J. Alvarez, C. Longeaud, J-P. Kleider, J. Schmidt
Strongly Correlated Electrons
Temperature-invariant magneto-optical Kerr effect in a noncollinear antiferromagnet
Camron Farhang, Weihang Lu, Yuchuan Yao et al. (+6 more)
Noncollinear antiferromagnets exhibit anomalous
Hall and magneto-optical Kerr effects driven by Berry
curvature despite negligible net magnetization, promising ultrafast spintronic applications. While both effects are theoretically expected to reveal the intrinsic Berry
curvature that serves as a spintronic
memory bit, their quantitative interpretation is complicated by additional temperature-dependent contributions superimposed on the
magnetic order parameter: extrinsic skew scattering in dc
Hall transport, and optical-resonance effects in visible-wavelength Kerr measurements. Here we perform polar Kerr measurements at the infrared telecommunication wavelength (1550 nm) on epitaxial, stoichiometric Mn3NiN single
crystal films, revealing for the first time a spontaneous Kerr signal that remains stable within a few percent over a 200 K range below the Néel temperature. This temperature-invariant intrinsic Kerr response contrasts with the strongly temperature-dependent anomalous
Hall effect in the same sample dominated by extrinsic skew scattering. Our findings establish infrared Kerr effect as a robust, local probe of Berry
curvature in noncollinear antiferromagnets, enabling quantitative characterization and advancing
antiferromagnetic spintronic technologies.
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All authors Camron Farhang, Weihang Lu, Yuchuan Yao, Pratap Pal, Shaofeng Han, Jian-Guo Zheng, Hua Chen, Chang-Beom Eom, Jing Xia
Mesoscale and Nanoscale Physics
Spin-Locked Helical Currents and Charge-Neutral Spin-Channel Pumping in Altermagnetic Nanotubes
Xin Chen, Zhen Han, Linyang Li et al. (+1 more)
Altermagnetism has been widely explored in 3D and 2D
crystals, but its one-dimensional realization remains largely unexplored. Here we propose an altermagnetic nanotube formed by rolling a 2D altermagnet, which converts \textcolor{black}{
symmetry-enforced directional
spin anisotropy in momentum space} into \textcolor{black}{
spin–chirality locking in the screw-symmetric geometry}. Unlike
curvature-induced magnetization in bent films, \textcolor{black}{the nanotube remains compensated and produces no net magnetization}. Two reciprocal effects emerge: (i) \textcolor{black}{
spin-selective} injection drives a helical current whose handedness is fixed by the
spin, yielding opposite-sign axial
magnetic fields; and (ii) a time-varying axial flux generates a circumferential Faraday field that drives \textcolor{black}{equal and opposite axial charge currents in the two fixed
spin channels, yielding a charge-neutral
spin-channel current in the open-
circuit weak-SOC limit}. \textcolor{black}{Explicit the first-principles calculations of the relaxed V$_2$Se$_2$O nanotube reveal
spin-resolved helical $|\psi|^2$ modulations near both band edges, while a parent-monolayer Wannier–Boltzmann calculation quantifies the energy-dependent
spin-odd transverse response and corresponding ideal thin-wall field scale.
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All authors Xin Chen, Zhen Han, Linyang Li, Mingwen Zhao
Materials Science · Cross-listed from physics.optics
High Uniformity GaN Micro-pyramids and Platelets by Selective Area Growth
Changhao Li, Vitaly Z. Zubialevich, Peter J. Parbrook et al. (+2 more)
The development of uniform GaN micro-pyramids and platelets via selective area growth is a critical step toward advancing III-nitride device technologies, particularly for micro-light-emitting diode applications. This work investigates the origins of morphological non-uniformity in micro-pyramids and micro-platelets grown by metal-organic chemical vapor deposition (MOCVD). We observe that a direct one-step growth approach leads to significant growth rate inhomogeneity across arrays. To shed light on this issue, we examine the mechanisms driving non-uniformity and explore process modifications aimed at mitigating these effects. Building on these insights, we propose a controlled multi-step growth strategy that combines sequen-tial growth and thermal treatment phases. This approach is demonstrated to enhance surface morphology and structural regularity. The work contributes to the broader objective of enabling scalable, high-precision GaN microstructure fabrication for next-generation optoelectronic applications.
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All authors Changhao Li, Vitaly Z. Zubialevich, Peter J. Parbrook, Brian Corbett, Zhi Li
Statistical Mechanics
Stochastic dynamics of quasiparticles in the hard rod gas
Seema Chahal, Indranil Mukherjee, Abhishek Dhar et al. (+2 more)
We consider a one-dimensional gas of hard rods, one of the simplest examples of an interacting integrable model. It is well known that the hydrodynamics of such integrable models can be understood by viewing the system as a gas of quasiparticles. Here, we explore the dynamics of individual quasiparticles for a variety of initial conditions of the background gas. The mean, variance, and two-time correlations are computed exactly and lead to a picture of quasiparticles as drifting Brownian particles. For the case of a homogeneous background, we show that the motion of two tagged quasiparticles is strongly correlated, and they move like a rigid rod at late times. Apart from a microscopic derivation based on the mapping to point particles, we provide an alternate derivation which emphasizes that quasiparticle fluctuations are related to initial phase-space fluctuations, which are carried over in time by Euler scale dynamics. For the homogeneous state, we use the Brownian motion picture to develop a Dean-Kawasaki-type fluctuating hydrodynamic theory, formally having the same structure as that derived recently by Ferrari and Olla. We discuss differences with existing proposals on the hydrodynamics of hard rods and some puzzles.
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All authors Seema Chahal, Indranil Mukherjee, Abhishek Dhar, Herbert Spohn, Anupam Kundu
Materials Science
Dara: Automated multiple-hypothesis phase identification and refinement from powder X-ray diffraction
Yuxing Fei, Matthew J. McDermott, Christopher L. Rom et al. (+2 more)
Powder X-ray diffraction (XRD) is a foundational technique for characterizing crystalline materials. However, the reliable interpretation of XRD patterns, particularly in multiphase systems, remains a manual and expertise-demanding task. As a characterization method that only provides structural information, multiple reference phases can often be fit to a single pattern, leading to potential misinterpretation when alternative solutions are overlooked. To ease humans' efforts and address the challenge, we introduce Dara (Data-driven Automated Rietveld Analysis), a framework designed to automate the robust identification and refinement of multiple phases from powder XRD data. Dara performs an exhaustive tree search over all plausible phase combinations within a given chemical space and validates each hypothesis using a robust Rietveld refinement routine (BGMN). Key features include structural database filtering, automatic clustering of isostructural phases during tree expansion, peak-matching-based scoring to identify promising phases for refinement. When ambiguity exists, Dara generates multiple hypothesis which can then be decided between by human experts or with further characteriztion tools. By enhancing the reliability and accuracy of phase identification, Dara enables scalable analysis of realistic complex XRD patterns and provides a foundation for integration into
multimodal characterization workflows, moving toward fully self-driving materials discovery.
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All authors Yuxing Fei, Matthew J. McDermott, Christopher L. Rom, Shilong Wang, Gerbrand Ceder
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Exact results for dissipation and steady creeping flow in three-dimensional chiral active fluids
Laura Meissner-Oszer, Bogdan Cichocki and Jeffrey C. Everts
Chiral active fluids consist of self-spinning particles that rotate due to continuous energy injection at the microscopic scale (e.g. by activity or an external field). The hydrodynamics of such fluids is described by antisymmetric contributions in the viscosity tensor - called odd viscosity - which are allowed by
symmetry due to the presence of a non-trivial
spin angular momentum density. By generalising the Helmholtz minimum dissipation
theorem to systems with odd viscosity, we show that incompressible three-dimensional odd fluids in the presence of sources that induce flow (e.g. surfaces that impose boundary conditions) admit a unique solution for their steady flow fields at low Reynolds number. Furthermore, we prove that such flows dissipate more energy than ordinary Stokes flow, provided that the flow field is affected by odd viscosity. As an example, we consider a model fluid described by one shear viscosity and one odd viscosity in the creeping flow regime. We explicitly compute the stress tensor for a fluid subjected to a point-force density. Finally, we compute exact results for the pressure and flow fields around a translating and rotating spherical particle from their singularity representations. From these solutions and our extended Helmholtz
theorem, we explain why a translating sphere dissipates more energy when odd viscosity is present, whereas a rotating sphere does not.
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Mesoscale and Nanoscale Physics
Adaptive Ising machine based on phase-locking of an auto-oscillator to a bi-harmonic external driving with noise
Eleonora Raimondo, Andrea Grimaldi, Vasyl Tyberkevych et al. (+6 more)
We introduce a universal theory of phase auto-oscillators driven by a bi harmonic signal (having frequency components close to single and double of the free-running oscillator frequency) with noise. With it, we show how deterministic phase locking and
stochastic phase slips can be continuously tuned by varying the relative amplitudes and frequencies of the driving components. Using, as an example, a
spin-torque nano-oscillator, we numerically validate this theory by implementing a deterministic Ising machine paradigm, a probabilistic one, and dual-mode operation of the two. This demonstration introduces the concept of adaptive Ising machines (AIM), a unified oscillator-based architecture that dynamically combines both regimes within the same hardware platform by properly tuning the amplitudes of the bi-harmonic driving relative to the noise strength. Benchmarking on different classes of combinatorial optimization problems, the AIM exhibits complementary performance compared to oscillator based Ising machines and probabilistic Ising machines, with adaptability to the specific problem class. This work introduces the first OIM capable of transitioning between deterministic and probabilistic computation taking advantage of a proper design of the trade-off between the strength of phase-locking of an auto-oscillator to a bi harmonic external driving and noise, opening a path toward scalable, CMOS compatible hardware for hybrid optimization and inference.
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All authors Eleonora Raimondo, Andrea Grimaldi, Vasyl Tyberkevych, Riccardo Tomasello, Anna Giordano, Mario Carpentieri, Andrei Slavin, Massimo Chiappini, Giovanni Finocchio
Materials Science
DFT-informed Design of Radiation-Resistant Dilute Ternary Cu Alloys
Vaibhav Vasudevan, Thomas Schuler, Pascal Bellon et al. (+1 more)
This research establishes a systematic, high-throughput computational framework for designing radiation-resistant, dilute ternary copper-based
alloys by addition of solutes that bind to vacancies and reduce their mobility, thus promoting interstitial-vacancy recombination. The first challenge in developing
alloys by this method is mitigating the vacancy-mediated solute drag effect, since density functional theory (DFT) calculations show that solutes that bind strongly to vacancies are also rapidly dragged to point-defect sinks, and thus removed from the
matrix. To overcome this issue, two types of solutes are added to the Cu
matrix: A first solute with a strong vacancy binding energy (B-type species) and another solute that binds to 'B' and is a slow diffuser in Cu (C-type species). Using DFT, 21 synergistic solute pairs are screened, with 'B'=Zr, Ge, Sn and 'C'=Fe, Co, Mo, Ni, Nb, W, Cr. Two promising
alloys, Cu(Zr,Co) and Cu(Zr,Fe) are then investigated in detail in the dilute regime.
Diffusion and solute drag in these
alloys are modeled using the kinetic cluster expansion approach (KineCluE) under irradiation conditions. It is shown that strong Zr-'C' thermodynamic binding, especially between Zr and Co, significantly reduces the mobility of Zr solute and suppresses the vacancy-mediated solute drag. Using an analytical framework for the standard five-jump frequency model for
diffusion in binary
alloys, it is found that vacancy-Zr-Co triplets disrupt the kinetic
circuits that promote solute drag in the binary
alloy by raising the dissociation barrier for the vacancy from the solute.
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All authors Vaibhav Vasudevan, Thomas Schuler, Pascal Bellon, Robert Averback
Mesoscale and Nanoscale Physics
Single-Scale Magnetoelastic Landau Quantization: Thermodynamics, Quantum Oscillations, and Metrology
Denise Assafrão, Faizuddin Ahmed and Edilberto O. Silva
We develop a unified, single-scale description of thermodynamics and
quantum oscillations in electronic systems with a uniform areal density of screw dislocations under a uniform
magnetic field. A single tunable gap, $\hbar|\omega_{eff}|$ with $\omega_{eff}=\omega_{c}+\omega_{cl}$, organizes all
equilibrium observables obtained from a compact harmonic-oscillator partition function: free energy, internal energy,
entropy, heat capacity, magnetization,
magnetic susceptibility, and magnetocaloric responses collapse onto universal
hyperbolic kernels in $x=\hbar|\omega_{eff}|/(2k_{B}T)$. We identify a compensated-field regime where the transverse gap closes and the heat capacity reaches an equipartition plateau, providing a sharp signature of magnetoelastic interference. In transport and torque, the same scale rigidly shifts the
Hall fan and compresses the $1/B$ period of de Haas-van Alphen and Shubnikov-de Haas oscillations when expressed in $1/B_{eff}$, enabling a phase-unwarping protocol that metrologizes the dislocation density from a single field sweep. In mesoscopic samples, boundary corrections to the Landau degeneracy generate finite-size calorimetric oscillations that diagnose the effective
magnetic length. Moderate disorder and weak interactions preserve the kernel structure while smoothing amplitudes. We outline an experimental roadmap combining on-chip calorimetry, torque magnetometry, and transport, and discuss device-level opportunities in caloritronics and strain engineering, magnetocaloric microcooling, magnetoelastic heat switching, and dilatometric transduction, where the single scale $\hbar|\omega_{eff}|$ enables rational design and optimization.
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