Mesoscale and Nanoscale Physics
Multistate Torsion in Zitterbewegung
Wojciech J. Jankowski
We derive nonlinear Zitterbewegung velocity of electrons augmented by band torsion in
crystals. The equation of motion with multistate
quantum geometric tensors and torsion culminates in transient nonlinear photocurrent responses distinct from the recently measured resonant steady-state photovoltaic effects induced by circularly polarized light.
Tomography protocols for measuring the multistate
quantum geometric torsion tensors are proposed.
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Quantum Gases · Cross-listed from physics.atom-ph
Spin-exchange interactions between circular Rydberg atoms over long times
Andrés Durán-Hernández, Gautier Creutzer, Aurore Alice Young et al. (+5 more)
Arrays of neutral atoms excited to Rydberg levels have emerged as one of the most promising platforms for
quantum computation and simulation. With the hope to outperform classical devices, the number of atoms has been increased by orders of magnitude. However, the interaction time, i.e., the maximum accumulated time during which an atom interacts with its neighbours, has been limited to a few microseconds only. This restrains the number of gates per atom or prevents the simulation of long-time dynamics of
quantum many-body systems. Here, we observe the
spin-exchange interaction between two
spin 1/2s encoded in
laser-trapped circular Rydberg atoms over more than $60\mu s$ and 40
spin-oscillation periods, improving the state of the art by an order of magnitude. These unprecedented timescales allow us to record for weak atomic trapping a collapse and revival of the
spin-exchange oscillation contrast induced by
spin-motion coupling. Our results constitute the first observation of this coupling with
laser-trapped Rydberg atoms. To counteract its detrimental effect for
quantum simulation, we demonstrate a novel dynamical decoupling method that prevents the collapse of the
spin oscillations. This method exploits the advantages of our recently developed hybrid platform that enables the measurement and the optical manipulation of long-lived circular Rydberg atoms with auxiliary Rydberg atoms. This work opens a direct route to long-duration
quantum simulation of strongly-interacting many-body systems.
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All authors Andrés Durán-Hernández, Gautier Creutzer, Aurore Alice Young, Abderrahmane Kassid, Yohann Machu, Jean-Michel Raimond, Michel Brune, Clément Sayrin
Materials Science
Nonrelativistic and Relativistic Contributions to Spin-Momentum Locking and Spin Photogalvanic Effect in an Altermagnetic Multiferroic
Giuseppe Cuono, Subhadeep Bandyopadhyay, Amar Fakhredine et al. (+6 more)
Altermagnetic multiferroics provide a platform where non-relativistic
spin-momentum locking (SML) coexists with relativistic
spin textures, yet disentangling their different origins remains challenging. Here, using first-principles density-functional-theory calculations and
symmetry analysis of the multipolar expansion of the
spin polarization, we investigate the altermagnetic multiferroic BaCuF4. Its dominant non-relativistic altermagnetic d-wave SML originates primarily from a CuF6 octahedral rotation coupled to the polar distortion and can therefore be reversed by ferroelectric switching. We show that
spin-orbit coupling generates additional
spin multipoles and, depending on the Neel-vector orientation, induces
spin canting and weak ferromagnetism. By exploiting the group-subgroup relations between
spin groups and
magnetic space groups, we then distinguish non-relativistic altermagnetic, canting-associated, and purely relativistic contributions to the SML. We further show that this hierarchy is encoded in the nonlinear
spin-photogalvanic response, whose
spin projection selectively probes contributions of different origins. These results establish a direct connection between the microscopic
spin texture and nonlinear
spin transport in altermagnetic multiferroics.
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All authors Giuseppe Cuono, Subhadeep Bandyopadhyay, Amar Fakhredine, Mathews Benny, Xujia Gong, Paolo Barone, Andrea Droghetti, Carmine Autieri, Silvia Picozzi
Mesoscale and Nanoscale Physics
Rotational symmetry and common-mode phase drift in a counter-wound S-shaped Aharonov–Bohm interferometer
Halil Serdar Solak and Afif Siddiki
We study common flux offsets in a three-dimensional InAs Aharonov-Bohm waveguide formed by two quarter-circle bends of opposite
curvature. Each bend contains a through-opening that separates two conducting arms and encloses an independently specified flux. For a
spin-independent, two-terminal model with ideal confined fluxes, microreversibility and a rotation exchanging the complete modules imply $\mathcal{T}(\phi_1,\phi_2)=\mathcal{T}(-\phi_2,-\phi_1)$. The counter-wound configuration is therefore stationary against common offsets, while the same-winding configuration is stationary against differential offsets. This constraint does not require cancellation of every interference phase, and it extends to a spatially uniform ambient field perpendicular to the plane of the guide, even though that field also penetrates the conductor. Three-dimensional scattering calculations at $R=350$ nm and $E_F\simeq 7.283$ meV retain three open orbital lead modes and strong reflection at the openings. The finest sampled counter-wound sweep has a visibility of approximately 3.56%; referring the grids to a common threshold gives an estimated continuum visibility of 2.6-2.9%. The response coefficients vary strongly with energy, while a 100 mK electron temperature retains about 98% of the visibility. For weak, purely common Gaussian phase noise, the leading transmission variance is quartic in noise amplitude, whereas the mean shift remains quadratic. Flux imbalance and asymmetric scalar potentials restore a linear response; symmetric scalar disorder preserves stationarity without guaranteeing high transmission. The proposed experimental test requires few-mode coherent transport, calibrated flux controls, and a
magnetic-source design whose leakage fields and
spin-dependent terms are assessed explicitly.
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Materials Science
Pronounced Site Preference in Cr-Doped Mn-Based M-Type Hexaferrites and Its Chemical Origins
Dylan Correll, Susheng Tan, Evan Wang et al. (+1 more)
Cation distribution plays a critical role in determining the properties of crystalline oxides. Understanding the chemical factors that govern cation distribution is therefore essential for the rational design of cation-ordered materials, particularly frustrated magnets in which structural disorder can strongly affect the
magnetic ground state. Here, we investigate the origin and
evolution of cation distribution in the extensively studied M-type hexaferrite structure using the first Mn-based M-type hexaferrite, KSb3Mn9O19, as a model system. A systematic Cr3+-doped series, KSb3(Mn1-xCrx)9O19, was examined using powder and single-
crystal X-ray diffraction, electron microscopy, and energy-dispersive X-ray spectroscopy. Cr3+ exhibits a pronounced preference for the Mn Kagome sublattice, accompanied by the
evolution of Mn vacancies and Mn3+/Sb3+ disorder on neighboring sites. Analysis of the local coordination environments and their
evolution with Cr content suggests that
crystal-field effects, chemical bonding, and local structural strain collectively govern this site selectivity. The
magnetic properties of the Cr-doped compounds show similar behaviors as the undoped parent compound, other than the doping-induced
spin-glass state at the highest Cr concentration, supported by heat capacity measurements. These results establish a chemical picture of cation site distribution and selection in M-type hexaferrites and demonstrate how substitution at one crystallographic site can induce coupled redistribution and disorder across neighboring sublattices. Moreover, this work establishes local coordination chemistry as a route toward understanding and ultimately controlling cation distribution in complex oxides, providing chemical design principles for structurally well-defined frustrated
magnetic materials.
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All authors Dylan Correll, Susheng Tan, Evan Wang, Xin Gui
Materials Science
Chemical-Disorder-Induced Non-metallic Transport in Thermodynamically Metallic Mo4TGa16Ge (T = Co, Rh or Ir)
Chaoguo Wang, Jiaqi Tian and Xin Gui
Flat-band electronic states can be highly sensitive to chemical perturbations, offering opportunities to access a broader range of electronic behaviors beyond that of parent materials. Here, we report the discovery of a new series of compounds, Mo4TGa16Ge (T = Co, Rh, or Ir), derived from the strongly correlated flat-band
superconductor, Mo4PtGa17, via nominally preserving the total valence electron counts. All three materials crystallize in a noncentrosymmetric cubic space group, F-43m, with Ge selectively occupying one of the Ga sites in the parent compound. Although the total electron count remains the same, Mo4TGa16Ge exhibits significantly distinct properties from Mo4PtGa17. Theoretical calculations predict metallic electronic structures with narrow, dominant Mo-d states at the Fermi energy, while low-temperature heat capacity results demonstrate finite Sommerfeld coefficients. However, electrical transport measurements show predominantly non-metallic behaviors with small observed activation energies, excluding the possibilities of conventional semiconducting behaviors. Combining chemical bonding analysis, electronic structure and compositional determination from X-ray crystallography and spectroscopy, we propose that the coexistence of the non-metallic transport features and the thermodynamically metallic behaviors can be attributed to the high sensitivity of the narrow-band materials to chemical disorders. Thus, the discovery and investigation of Mo4TGa16Ge provide a chemically tunable platform for studying disorder-controlled transport in flat-band intermetallics.
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Materials Science
Switching Anomalous Hall and Nernst Responses by Nonmagnetic N Occupation at Fixed Noncoplanar Mn Antiferromagnetic Order
Xin Liu, Jiyuan Xu, Li Ma et al. (+4 more)
Nonmagnetic atomic occupation can control anomalous transverse transport by modifying
magnetic symmetry without changing the underlying
magnetic order. We demonstrate this effect using controlled $\gamma$-Mn, Mn$_4$N, and MnN reference states with the same
lattice constant and identical noncoplanar all-in-all-out Mn
magnetic configurations, while varying only the occupation of the N sublattice. The anomalous Hall and anomalous Nernst responses exhibit a pronounced zero–finite–zero
evolution across the series despite the unchanged Mn
spin order. In $\gamma$-Mn and MnN, the high
magnetic symmetry enforces complete cancellation of the Brillouin-zone-integrated Berry
curvature. In Mn$_4$N, N occupation lowers the
magnetic symmetry while preserving inversion and breaking the relevant twofold rotational
symmetries, thereby lifting the cancellation constraint and permitting an uncompensated Berry-
curvature contribution along the [111] direction. The resulting finite anomalous Hall conductivity reaches $-126$~S/cm near the Fermi level. These results establish nonmagnetic sublattice occupation as a
symmetry-control parameter for Berry-
curvature-driven transport in compensated antiferromagnets, independent of changes in the
magnetic order.
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All authors Xin Liu, Jiyuan Xu, Li Ma, Guoke Li, Dewei Zhao, Congmian Zhen, Denglu Hou
Soft Condensed Matter
Defect Organization in Coexisting Hexagonal and Square Lattices on Ellipsoids
Wenyu Liu, Han Xie, Baohui Li et al. (+2 more)
Curvature and
topology jointly organize defects in two-dimensional
crystals, but their combined role remains unresolved when competing
lattice symmetries coexist with spatially varying
curvature. We use simulated-annealing Langevin dynamics to study Hertzian particles forming coexisting hexagonal (Hex) and square (Sq)
lattices on prolate and oblate ellipsoids. Mapping reduced density and aspect ratio reveals a broad sequence of scar and domain-based morphologies in both Hex-dominant and Sq-dominant backgrounds. Latitude-resolved comparisons show that Gaussian
curvature biases defects toward its maxima under weak deformation. Strong prolateness, however, confines high
curvature to small polar caps that cannot independently accommodate all defect motifs. Defects then spread toward lower-
curvature latitudes to relieve defect crowding and elastic repulsion. In the Hex-dominant regime, this competition drives vertex-contacted domains with neutralized corner contacts, and compensating positive defects locate away from the poles. The Sq-dominant regime features Hex-rich triangular domains, bridged states, and linear or open scars similarly reorganized by
curvature anisotropy. On oblate ellipsoids, the extended equatorial high-
curvature belt allows defects to separate azimuthally while remaining
curvature-localized. This work elucidates that nonuniform
curvature can engineer rich defect patterns by selecting the spatial distribution of topological charge and the connectivity of finite defect motifs.
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All authors Wenyu Liu, Han Xie, Baohui Li, Jeff Z.Y. Chen, Yao Li
Soft Condensed Matter
A Bioinspired Magnetothermally Triggered Capsule for Rapid Microrobot Release
Mengfan Zhang, Zike Chen, Zhihao Lv et al. (+3 more)
Capsules are attractive platforms for microrobot delivery, combining structural simplicity with protected delivery and rapid release remains challenging. Inspired by the latched spring mechanism of Impatiens balsamina seed dispersal, a magnetothermally triggered capsule integrates a phase-change hydrogel latch, a monostable cover that serves as an elastic spring, and a payload-carrying base. Mechanical analysis guides the cover design to avoid bistability after assembly and premature hydrogel latch rupture before triggering. During transport, the hydrogel constrains the inverted cover. Under an alternating
magnetic field, Fe3O4-mediated heating softens the hydrogel and induces cohesive failure, releasing stored energy to drive capsule opening and microrobot ejection. The capsule opens within 50 ms after hydrogel softening and ejects microrobots at an estimated initial velocity of 1.0 m/s. Demonstrations on a three-dimensional platform and ex vivo porcine stomach establish protected delivery, target-site opening, and post-release actuation.
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All authors Mengfan Zhang, Zike Chen, Zhihao Lv, Zheng Jia, Rui Xiao, Guoyong Mao
Statistical Mechanics
Quantum Statistical Thermal Engine at the BCS-BEC crossover
Santiago Henríquez Lira, Felipe Isaule, Martín HvE Groves et al. (+3 more)
We propose a
quantum heat engine based on a two-component Fermi gas with s-wave contact interaction, operating across the BCS-BEC crossover. The work is extracted from the statistical properties of the gas, which are controlled by the interaction, rather than relying solely on compression and expansion stages. Using the functional renormalization group formalism, we obtain the equation of state in a non-perturbative form along the crossover, encompassing the superfluid-normal phase transition. The cycle combines isentropic density strokes, isochoric thermalization, and isothermal interaction sweeps. This construction makes it possible to integrate features of both Otto and Carnot cycles, in which the system simultaneously saturates both efficiency limits without the net work vanishing. In the absence of density variations, the cycle reduces to a statistical Stirling-like engine, in which the work generated arises exclusively from the interaction, achieving efficiencies up to $38\%$. A pronounced asymmetry emerges through the crossover, giving rise to distinct operating regimes depending on the trajectory followed in the phase diagram. Consequently, the same architecture can be tuned to function as an engine, refrigerator, accelerator, or heater. These findings highlight pairing correlations as a versatile thermodynamic resource for
quantum heat machines.
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All authors Santiago Henríquez Lira, Felipe Isaule, Martín HvE Groves, Francisco J. Peña, Patricio Vargas, Thomás Fogarty
Materials Science · Cross-listed from physics.chem-ph
What Does a Semilocal Machine-Learning Correction Actually Learn? Size-Dependent Errors across Four Parent Functionals
Abhishek Bhattacharjee, Kishan Kumar Mohanta, Subrata Jana et al. (+1 more)
Machine-learning (ML) corrections to density functional approximations (DFAs) offer a route to improving electronic-structure predictions while retaining the efficiency of semilocal functionals. An important question is whether such corrections learn transferable improvements or instead compensate for errors specific to the parent functional. Here, we address this question by applying the semilocal ML correction of Wang et al. [J.~Chem.~Phys.~158, 154107 (2023)] to PBE, B3LYP, SCAN, and r$^2$SCAN, while keeping the network architecture, loss function, training set, and optimization protocol unchanged. We find that the learned correction develops a systematic size-dependent contribution to atomization energies for all four parents, with $|r|\geq0.9999$ along the $n$-alkane series, where r is the Pearson coefficient of the linear fit. Its magnitude and sign depend systematically on the parent: the correction partially compensates the size-dependent errors of PBE and B3LYP, but introduces substantial size-dependent contributions for SCAN and r$^2$SCAN, whose parent errors show little size dependence. In contrast, ionization potentials, electron affinities, and isomerization energies are largely unaffected. Spatial decomposition further reveals distinct origins of this extensive contribution, with bonding regions dominating for B3LYP, SCAN, and r$^2$SCAN and core regions dominating for PBE. These results show that the global-energy ML correction is strongly dependent on the error structure of its parent DFA, highlighting size-dependent error accumulation as a critical consideration in the assessment and development of ML-enhanced density functionals.
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All authors Abhishek Bhattacharjee, Kishan Kumar Mohanta, Subrata Jana, Prasanjit Samal
Materials Science
Screening of Coulomb Interactions in MoS2 Nanoribbons: Enhanced Coulomb interactions, Antiscreening, and Edge Magnetism
A. Montaghemi, H. Hadipour, A. Khademi et al. (+1 more)
MoS2 has attracted significant
attention for its promising applications in optoelectronics, owing to the remarkable stability of its
excitons and trions. These quasiparticles have large binding energies that arise from the MoS2 moderate band gap and the unconventional screening of Coulomb interactions in low dimensions. Here, we investigate the screening of long-range Coulomb interactions in the 1H and 1T' phases of MoS2 across different dimensionalities, with particular emphasis on nanoribbons. Our analysis is based on first-principles calculations combined with the constrained random-phase approximation. This work presents a comparative study of MoS2, h-BN, black phosphorene, and
graphene nanoribbons, with emphasis on the role of Coulomb interactions in shaping their electronic and
magnetic properties. In one-dimensional nanoribbons,
quantum confinement leads to a substantial enhancement of Coulomb interactions relative to 2D MoS2. Calculations show that the Hubbard U increases from 2.6 eV in the 2D system to nearly 3.5 eV in the semiconducting nanoribbons. In these systems, the Coulomb interaction is long-ranged, with its tail extending over more than 100 A, nearly twice of that in the 2D structure. The presence of asymmetric edge states involving d and p orbitals in non-hydrogen-passivated zigzag MoS2 nanoribbons, in contrast to phosphorene, h-BN, and
graphene nanoribbons, results in a finite net magnetization.
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All authors A. Montaghemi, H. Hadipour, A. Khademi, A. Yazdani
Materials Science
Operando Surface Probe Microscopy Reveals Electrochemical Origins of Reliability Variability in Hafnia Ferroelectrics
Anudeep Tullibilli, Kartick Biswas, Shubham Kumar Parate et al. (+1 more)
Device-to-device and sample-to-sample variability remains a major obstacle to the reliable implementation of hafnia-based ferroelectrics, even in nominally identical structures fabricated under similar processing conditions. This highlights the need for operando diagnostic probes that provide process-relevant feedback beyond conventional structural phase analysis. Here, we demonstrate that operando nanoscale surface measurements serve as sensitive probe of the local electrochemical processes governing reliability in hafnia ferroelectric devices. Using epitaxial rhombohedral Y:HfO2 films grown on La0.67Sr0.33MnO3 (LSMO)-buffered SrTiO3 as a model system, we combine operando atomic force microscopy, conductive AFM, piezoresponse force microscopy, and correlative STEM-EELS to directly link surface
evolution with interfacial electrochemistry. Devices exhibiting wake-up show a spatially uniform increase in surface height, arising from homogeneous oxidation of the LSMO electrode followed by oxygen migration into the ferroelectric layer during polarization switching. In contrast, leaky devices display pronounced surface roughening and blister formation, originating from spatially inhomogeneous oxidation states in the pristine LSMO electrode that promote competing oxygen
evolution reactions at the LSMO/Y:HfO2 interface. The accompanying electron generation produces leakage which is transient. Guided by these mechanistic insights, we introduce simple modifications to the processing conditions, without altering the optimized ferroelectric phase, that suppress the competing electrochemical pathways and reproducibly yield 100% ferroelectric devices. More broadly, this work establishes operando surface
evolution as a powerful nanoscale diagnostic of hidden electrochemical processes and provides a practical route for improving the reliability and reproducibility of hafnia-based ferroelectric devices.
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All authors Anudeep Tullibilli, Kartick Biswas, Shubham Kumar Parate, Pavan Nukala
Statistical Mechanics
Exact anomalous current fluctuations in the strong-anisotropy limit of the XXZ chain
Taiki Ishiyama, Taiga Kurose, Kazuya Fujimoto et al. (+1 more)
We study
spin-current fluctuations of the folded XXZ chain, which describes the strong-anisotropy limit of the XXZ chain. We obtain an exact expression for the moment-generating function of the time-integrated
spin current at infinite temperature. A long-time asymptotic analysis establishes that the rescaled time-integrated current converges to a non-Gaussian distribution described by the M-Wright function. The derivation relies on a nonlocal map to the one-dimensional t-0 model and its exact
spin-charge separation. By extending this approach, we also show that the dynamical correlation function of the
spins summed over two adjacent sites exhibits a diffusive Gaussian profile at long times.
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All authors Taiki Ishiyama, Taiga Kurose, Kazuya Fujimoto, Tomohiro Sasamoto
Statistical Mechanics
Phase separation, morphology, and metastability in the three-dimensional active Potts model
Aditya Kumar Dutta and Raja Paul
We study the three-dimensional active Potts model (APM) on a cubic
lattice with 2, 4, and 6 orientational states. The steady-state phase diagrams exhibit low-density gaseous, high-density polar
liquid, and
liquid–gas coexistence phases, with the phase behavior controlled by density, temperature, and propulsion speed and retaining the main features of the previously studied two-dimensional APM. At weak propulsion, the dense phase forms a slab perpendicular to its direction of motion. With increasing propulsion speed, this morphology persists for the 2-state model, whereas the dense phases for 4 and 6 states reorient and propagate along their longitudinal direction. For the 6-state model, the reoriented dense phase further develops a cylindrical morphology. We also examine the stability of polar
liquids against artificially introduced droplets using microscopic simulations and coarse-grained hydrodynamic equations. At high propulsion speeds, counter-propagating droplets can partially modify the initial polar state, while transverse droplets can completely alter it, demonstrating the metastable nature of polar
liquids in the three-dimensional active Potts model.
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Soft Condensed Matter
Stiffness-dependent Dielectric Relaxation in Thermoreversible Microgels: Effects of Temperature and Strain
Sayantan Chanda, Sonali Vasant Kawale and Ranjini Bandyopadhyay
We investigate how particle stiffness governs length-scale-dependent relaxation dynamics in dense suspensions of thermoresponsive PNIPAM microgels subjected to temperature variations and large amplitude oscillatory shear. By combining dielectric spectroscopy with rheometric measurements, we directly correlate microscopic polarization fluctuation dynamics with macroscopic mechanical relaxation. Highly crosslinked, stiffer microgels exhibit longer dielectric relaxation times across a broad temperature range and strain-induced slowing down, whereas softer, open-network microgels exhibit nearly strain-independent dielectric dynamics. Below the volume phase transition temperature (VPTT), macroscopic bulk stress relaxation experiments reveal that suspensions of the softest particles relax most rapidly. For the stiffer microgel suspensions, however, the dynamics decouple: bulk stress relaxation speeds up with increasing stiffness even as dielectric relaxation slows down. Above the VPTT, softer particles undergo greater volume collapse, leading to very rapid bulk stress relaxation. Besides exhibiting slower stress decay, stiffer microgel suspensions also undergo shear-induced structural regeneration during the later stages of deformation. These findings demonstrate that particle stiffness and internal architecture govern relaxation pathways across microscopic and macroscopic length scales, thereby providing a framework for designing adaptive soft metamaterials, stress-dissipative coatings, and self-healing robotic materials.
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Mesoscale and Nanoscale Physics
Nonlinear optical responses of semiconducting graphene nanoribbons: Strong constraint from a hidden symmetry
Jiawei Ruan, Weichen Tang, Yang-Hao Chan et al. (+3 more)
Nonlinear optical (NLO) responses are powerful tools for probing material structures, as they are highly sensitive to spatial
symmetries. For instance, it is well known that having inversion
symmetry forbids even-order NLO effects. Here, we show that nonspatial
symmetries can also significantly constrain NLO responses. In
graphene nanoribbons (GNRs) with bipartite-
lattice structures, we identify the approximate bipartite-
lattice particle-hole (BLPH)
symmetry strongly suppresses even-order NLO effects, even for systems with no inversion
symmetry. Importantly, we demonstrate that this approximate
symmetry enables the optical generation of nearly pure
spin shift currents in ferromagnetic GNRs, with the charge shift currents strongly suppressed. The
spin orientation of these photo-induced DC
spin currents can be easily tuned by an external
magnetic field, providing distinct advantages over previous schemes for generating pure
spin shift currents in antiferromagnetic systems. We illustrate our findings using a recently synthesized ferromagnetic Janus GNR. Our results underscore the significance of an overlooked
symmetry aspect of NLO responses and highlight
magnetic GNRs as promising candidates for spintronic devices.
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All authors Jiawei Ruan, Weichen Tang, Yang-Hao Chan, Chen Hu, Xiaoxun Gong, Steven G. Louie
Materials Science · Cross-listed from physics.ins-det
Quantitative Interleaved-Pulse Acquisition Extends the Range of Isotope-Ratio Measurements in ToF-SIMS
Anton V. Ievlev
Isotope ratios underpin tracer studies of transport in oxides, battery materials, and biological systems, yet time-of-flight secondary ion mass spectrometry (ToF-SIMS) struggles to quantify ratios whose members differ in intensity by orders of magnitude: a primary-ion pulse long enough to count the minor isotope precisely can saturate the major isotope, whereas a pulse short enough to keep the major isotope linear yields too few minor-isotope counts. We show that multi-pulse-width acquisition yields quantitative isotope ratios when a dose factor measured within each crater links the phases and each isotope is taken only from phases in which it remains linear; we call this quantitative reconstruction interleaved-pulse acquisition. Pulse widths are selected from measured transfer curves and peak shapes. On thermal SiO2, a tuned (6, 35) ns pair achieves the same per-layer precision as short-pulse acquisition with a 13-fold reduction in the number of analysis frames. On 18O-enriched WOx films, interleaving extends the quantifiable range at the low-fraction end by about 14-fold. Across isotope ratios spanning approximately 1:500 to 1:1, the interleaved reconstruction agrees with the corresponding linear reference measurements, showing no measurable bias introduced by interleaving, and natural-abundance ratios of oxygen, strontium and titanium are reproduced within several percent. The method requires no hardware additions and enables depth-resolved isotope-ratio measurements over a wide range within a single crater.
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Materials Science
Topological Hall Effect Induced by Chiral Spin Textures at the Ferroelectric/Ferromagnetic Interface
Jingkuan Xiao, Yaqing Han, Jianfeng Guo et al. (+25 more)
Chiral
spin textures, largely driven by the Dzyaloshinskii-Moriya interaction, offer significant potential for next-generation computing technologies due to their chirality and topological stability. Ferroelectric/ferromagnetic van der Waals
heterostructures are particularly appealing because they can combine interfacial inversion-
symmetry breaking and
spin-orbit coupling to promote interfacial Dzyaloshinskii-Moriya interaction, while switchable ferroelectric polarization provides a nonvolatile tuning knob. This study investigates interfacial chiral
spin textures in few-layer Fe$_3$GeTe$_2$/$\alpha$-In$_2$Se$_3$
heterostructures. Two groups of topological Hall signals are identified just below and above the coercive field, and thickness-dependent transport reveals a notable reduction in critical temperature with increasing Fe$_3$GeTe$_2$ layer thickness. Low-temperature
magnetic force microscopy images reveal two types of
magnetic bubbles with opposite
magnetic contrasts near the coercive field, each associated with distinct topological Hall signals. Together with atomistic
spin-dynamics simulations and first-principles calculations, these results support the formation of interfacial DMI-stabilized chiral
spin textures. Switching the ferroelectric polarization of the $\alpha$-In$_2$Se$_3$ layer further enables nonvolatile modulation of both anomalous and topological Hall effects. The resulting ferroelectric and
magnetic bistabilities generate four distinguishable Hall resistance states programmable by electric and
magnetic fields. These findings highlight the potential of van der Waals interfaces for advanced device applications.
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All authors Jingkuan Xiao, Yaqing Han, Jianfeng Guo, Renjun Du, Jiawei Jiang, Baoshan Cui, Runnong Zhou, Siqin Wang, Siqi Jiang, Fuzhuo Lian, Di Zhang, Guodong Ma, Jiabei Huang, Zhaochen Qu, Wanting Xu, Kenji Watanabe, Takashi Taniguchi, Alexander S. Mayorov, Jinsheng Wen, Haifeng Ding, Gong Chen, Ahmet Avsar, Hongxin Yang, Lihong Bao, Hong-Jun Gao, Shiyu Zhu, Lei Wang, Geliang Yu
Disordered Systems and Neural Networks · Cross-listed from q-bio.NC
An adaptive fractional state links circuit mechanisms to cortical dynamics across the visual hierarchy
Brendan Harris and Pulin Gong
Cortical
circuits must respond flexibly to new inputs while integrating information about the past, yet the way in which neural activity reconciles these competing demands remains unclear. Combining Neuropixels recordings from six mouse visual areas with mechanistic
circuit modeling, we identify a dynamical regime in which heavy-tailed superdiffusive fluctuations coexist with long-range temporal dependence and oscillations. We formalize this regime as the adaptive fractional (AF) state, using an effective mean-field theory in which spatial and temporal fractional derivatives capture heavy-tailed excursions and long-range
memory, respectively. We find that dynamical exponents characterizing the AF state vary systematically across the visual hierarchy: higher visual areas exhibit weaker superdiffusion and stronger temporal
memory. In the
circuit model, this hierarchical shift emerges from a progressive weakening of effective inhibition. These findings extend the classical hierarchy of timescales to a hierarchy of dynamical regimes and suggest that the AF state allows cortical areas to jointly express rapid responses and long-term temporal integration.
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Strongly Correlated Electrons · Cross-listed from hep-lat
Boundary Condition dependent Universality Classes on a Hyperbolic Lattice
Pallabi Dey, Debasish Banerjee, Arnab Kundu et al. (+1 more)
We study the ferromagnetic Ising model on finite
hyperbolic tessellations of Euclidean AdS$_2$ with open and wired boundary conditions. Because a finite fraction of
spins remains at the boundary as the
lattice grows, these conditions select distinct thermodynamic behaviours. In the $\{5,4\}$ tessellation, Monte-Carlo simulations using efficient worm
algorithms on open boundaries (OBC) yield a transition near $\beta_c J=0.632(3)$, with susceptibility data collapsing under scaling by the total number of
spins $N$. The fitted finite-size exponents, $1/\bar{\nu} \simeq 0.162$ and $\gamma/\bar{\nu} \simeq 0.743$, differ substantially from the mean-field volume scaling. Wired boundaries (WBC), which correlate boundary
spins, instead show a transition around $\beta_c J=0.348(4)$ to an ordered phase consistent with the mean-field exponents. While the mean-field criticality with WBC is consistent with previous studies and with the suppression of independent boundary fluctuations, the OBC exponents hint at the presence of a new universality class. Results from other tessellations support the robustness of the observed scaling with OBC. We discuss a possible route to interpolate between the different boundary conditions. Our findings show that boundary dynamics must be specified when characterizing critical behaviour on
hyperbolic lattices.
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All authors Pallabi Dey, Debasish Banerjee, Arnab Kundu, Ritam Sinha
Materials Science
Vapor phase growth and characterization of van der Waals BiSbTeSe platelets on semiconducting MoS2
M. Zhezhu, V. Torosyan, V. Mehrabyan et al. (+1 more)
Three dimensional topological
insulators of the tetradymite family, such as BiSbTeSe (BSTS), are attractive for spintronic and
quantum device applications because of their compensated, bulk-insulating character. Nanostructured BSTS platelets are promising for practical TI based devices. However, their growth often requires complex equipment, organometallic precursors, or electrically insulating substrates. Simple growth on technologically relevant semiconducting substrates remains largely unexplored. Here, we report the vapor phase growth of van der Waals BSTS platelets directly on semiconducting MoS2 using a presynthesized BiSbTe1.5Se1.5
crystal as the source material. The grown BSTS platelets exhibit thicknesses ranging from 4 nm to 246 nm, with an average lateral size of 1.4 mkm for individual platelets. Raman spectra of platelets, acquired in correlation with AFM thickness measurements, reveal contributions from both BSTS and the underlying MoS2 substrate. Among the characteristic BSTS modes, A21g mode shows the highest sensitivity to platelet thickness and local composition. EDS analysis reveals a systematic thickness dependence of the platelet composition, with an apparent crossover around 49 nm that coincides with a change in the thickness dependence of the low-wavenumber component of the E2g Raman band. This correlation suggests a composition-related origin of the Raman behavior, with the compositional variations tentatively attributed to the differential
volatility of the constituent elements during growth. These results demonstrate that MoS2 is a promising van der Waals platform for BSTS deposition and provide a structural and compositional baseline for future studies of BSTS-MoS2
heterostructures.
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All authors M. Zhezhu, V. Torosyan, V. Mehrabyan, A. Vasilev
Mesoscale and Nanoscale Physics
Atomic-scale control of spin transport in exchange-coupled molecules
A. Fétida, R. Robles, F. Scheurer et al. (+4 more)
Spin transport between coupled
spins is governed by tunneling and exchange interactions, yet their microscopic relation in real space has remained experimentally elusive. To address this, we functionalize the tip of a scanning tunneling microscope with a single molecule and use it as a movable
spin sensor positioned above a second molecule on a ferromagnetic surface, forming an exchange-coupled molecular junction. From the same spectroscopic
dataset, we independently extract the junction conductance, exchange coupling, and
spin polarization with atomic-scale resolution. Conductance and exchange display nearly identical spatial dependences, consistent with a minimal Hubbard description in which both are governed by the same hopping
matrix between the molecular frontier orbitals. In contrast, the
spin polarization depends on the orbital composition and the relative weight of the resulting transport channels. These results establish a real-space connection between tunneling, exchange, and
spin transport in magnetically coupled molecules.
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All authors A. Fétida, R. Robles, F. Scheurer, M. Romeo, J. Kröger, N. Lorente, L. Limot
Statistical Mechanics
Anomalous transport in periodic systems driven by active fluctuations
Karol Białas
This dissertation investigates the transport of Brownian particles driven by active fluctuations in periodic potential landscapes. Unlike thermal noise, active fluctuations break detailed balance and violate the fluctuation-dissipation
theorem. They model self-propulsion mechanisms and active-bath interactions in biological and synthetic micro-systems. By focusing on white Poisson shot noise with non-Gaussian amplitude statistics, this work systematically uncovers the mechanisms governing three major transport anomalies: giant transport enhancement, absolute negative mobility, and the ratchet effect. Combining Monte Carlo simulations with analytical modeling, this work demonstrates that active fluctuations adhering to a bidirectional skew-normal amplitude distribution enhance directed velocity compared to the free-particle by several orders of magnitude. This giant transport enhancement is fully quantified via a phenomenological jump-relaxation model that decouples particle displacement into instantaneous
stochastic jumps and deterministic relaxation towards potential minimum. Extending this model to inertial dynamics reveals that finite particle mass m acts as a dynamic control parameter capable of strengthening, weakening, constructively inducing, or completely suppressing transport enhancement depending on noise variance. Furthermore, an ultra-minimal model for absolute negative mobility is established in a one-dimensional, purely overdamped system, showing that discontinuous shot noise drives transport opposite to an applied bias without requiring particle inertia, nonlinearity of spatially periodic potential, or explicit time-dependent periodic driving. Conversely, under an alternative scaling of the average
stochastic force, an asymmetric distribution of fluctuation amplitudes generates net directed transport through a tilting ratchet effect in the zero-bias limit.
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Statistical Mechanics
Scale invariance, fractal dynamics, and critical exponents at the phase transition
Henrique Alves de Lima
We propose that, at criticality,
equilibrium dynamics effectively evolves on a fractal subspace rather than throughout the full Euclidean space. Starting from Fisher's formulation of the order-parameter correlation function, we interpret the anomalous critical exponent $\eta$ geometrically through a correlation fractal dimension associated with this effective subspace. Using fractional-calculus tools, we derive a form of the correlation function that recovers critical behavior below the upper critical dimension and obtain an explicit relation between $\eta$ and a fractal dimension $d_R$ linked to the Riesz fractional derivative. We also examine the Rushbrooke scaling relation and investigate critical behavior in non-integer-dimensional and disordered systems. In the disordered case, controlled by a parameter $\sigma$, we test the range over which the proposed
geometric interpretation remains valid. The results connect scaling laws, critical exponents, correlations, and fractal geometry, suggesting that the anomalous behavior observed at criticality can be understood as a consequence of dynamics constrained to an effective fractal subspace.
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Quantum Gases · Cross-listed from hep-th
Active normal-fluid feedback in quantum turbulence from holography
Yu-Ping An, Li Li, Makoto Tsubota et al. (+2 more)
The two-fluid model provides a powerful phenomenological framework for superfluids, where components interact through
vortex-induced mutual friction.
Quantum turbulence in such coupled two-fluid systems has become a central theme in low-temperature physics. However, the fundamental incompatibility between discrete
vortex-line and continuum descriptions has historically forced reliance on phenomenological parameters. Here, we present an ab initio holographic simulation of this active two-fluid dynamics. Using a fully backreacted gravitational model, we intrinsically incorporate reciprocal momentum exchange and finite-temperature dissipation without empirical inputs. Contrasting continuously driven and freely decaying
turbulence, we uncover pronounced non-Gaussian tails and spatial anisotropy in the normal-fluid velocity statistics, arising directly from the dynamical quantized
vortex backreaction. Raising the temperature suppresses normal-fluid velocity fluctuations despite increasing the
vortex density. This suppression is unambiguously traced to the thermal depletion of the superfluid condensate. Our results establish holographic duality as a rigorous first-principles framework for
quantum turbulence, revealing the active role of the normal fluid far from
equilibrium and yielding predictions for ongoing cold-atom and superfluid experiments.
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All authors Yu-Ping An, Li Li, Makoto Tsubota, Sebastian Waeber, Hua-Bi Zeng
Soft Condensed Matter · Cross-listed from physics.plasm-ph
Rectification of plasma-powered active matter into macroscopic work
Ting-yu Yao, Shuo Wang, Shao-peng Li et al. (+3 more)
Plasmas sustain strong energy and momentum flux, yet this activity is typically treated as a dissipative loss channel rather than a usable resource, and its conversion into macroscopic work remains challenging. Here we demonstrate a
plasma-powered active engine by coupling self-propelled micromotors to ratchet rectification. Dielectric microspheres in the
plasma sheath spontaneously develop asymmetric surface charging and undergo a Quincke rotational instability, forming fast micromotors that extract energy directly from the
plasma. Their
stochastic impacts are rectified by a sawtooth rotor into a directed angular-momentum flux that drives steady rotation, while an outer asymmetric gear organizes the active bath into coherent circulation to amplify torque transfer. Operating in an inertia-relevant regime, the engine achieves orders-of-magnitude enhancements in both power output and end-to-end efficiency compared with
liquid-phase active engines, and remains functional down to the single-micromotor limit. More broadly, our results establish a general route to rectify nonequilibrium
plasma activity for macroscopic work.
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All authors Ting-yu Yao, Shuo Wang, Shao-peng Li, Ming-hang Zhao, Bao-quan Ai, Ya-feng He
Materials Science · Cross-listed from quant-ph
L-band single-photon generation from a cavity-coupled silicon C-center
Carolina Crosta, Kyu-Young Kim, Purbita Purkayastha et al. (+7 more)
Monolithic integration of single-
photon sources into silicon photonics offers a compelling solution for realizing scalable
quantum telecommunication architectures. Among the candidate silicon color centers, the C-center features a zero-
phonon emission in the telecom L-band, corresponding to the spectral window of minimum transmission loss in optical fibers. Despite this advantage, isolating single C-centers has remained an unrealized challenge in solid-state
quantum optics. In this work, we report the isolation of a single silicon C-center. We enhance the spontaneous emission rate of the zero-
phonon line by coupling the single emitter to a nanophotonic
crystal cavity, observing a fivefold reduction in the excited-state lifetime compared to bulk conditions, which corresponds to a Purcell factor lower bound of 33. Second-order autocorrelation measurements confirm single-
photon emission from the investigated defect, obtaining an optical purity of $g^{(2)}(0) = 0.23$ without background correction. Our results establish a native telecom L-band
quantum light source in silicon, laying the foundation for ultra-low-loss and long-distance
quantum applications.
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All authors Carolina Crosta, Kyu-Young Kim, Purbita Purkayastha, Abhijit Biswas, Jasvith Raj Basani, Amirehsan Alizadehherfati, Amirehsan Boreiri, Chang-Min Lee, Fabio Pezzoli, Edo Waks
Statistical Mechanics
The Spectral Cost of Detecting Nonequilibrium at Finite Temporal Resolution
Murad Aznagulov
A detector that cannot take two snapshots closer than a time $\tau_0$ still identifies a fully observed finite Markov generator exactly, provided its gaps are randomized by two clocks. Identification is not detection. For a normal nonequilibrium network, the number of snapshots needed to reject every hidden
equilibrium explanation grows as $e^{2\gamma_{\mathrm{irr}}\tau_0}$, where $\gamma_{\mathrm{irr}}$ is the slowest damping of rotating modes. No adaptive schedule beats this rate, and a test on one dependent trajectory attains it.
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Materials Science
Engineering Synaptic Dynamics in Ag-Modified TaO$_x$ Memristive Devices
R. Leal Martir, W. Quiñonez, A.J.T. van der Ree et al. (+4 more)
Engineering not only the magnitude but also the dynamics of synaptic weight updates is an important challenge for memristive neuromorphic hardware. Here, we show that Ag modification of TaO$_x$ memristors introduces an electrically selectable degree of freedom in synaptic depression through the interplay between Ag-related and oxygen-vacancy dynamics. Reference devices exhibit conventional bipolar switching, whereas Ag-modified devices display symmetric table-with-legs hysteresis loops, metastable intermediate states, and a strongly non-monotonic dependence of depression dynamics on programming amplitude. By varying only the pulse amplitude, the same device can be driven among three regimes: gradual sigmoidal depression, an abrupt update concentrated within a few pulses, and a broadly distributed
evolution extending over more than one hundred pulses. A minimal coupled-state model, in which a vacancy-related switching variable interacts with a slower Ag-related internal degree of freedom, reproduces this gradual–abrupt–gradual crossover using two individually monotonic field-activated processes. The functional impact is assessed in a memristor-based multilayer perceptron. For MNIST, the abrupt, sigmoidal, and slowly evolving responses yield accuracies of approximately 50%, 85%, and 88%, respectively, while the gradual regime reaches approximately 72% for Fashion-MNIST. These results show that coupling Ag-related and oxygen-vacancy dynamics can transform synaptic depression from a fixed device characteristic into an electrically programmable property.
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All authors R. Leal Martir, W. Quiñonez, A.J.T. van der Ree, M. H. Aguirre, G. Palasantzas, M. J. Sánchez, D. Rubi