Strongly Correlated Electrons · Cross-listed from hep-th
Monopoles, Center Vortices, Confinement in (3+1)d, and the Lens-Space Twisted Partition Function
Yui Hayashi and Yuya Tanizaki
We propose the gauge-invariant criteria of center-
vortex condensation and monopole condensation using the $\mathbb{Z}_N^{[1]}$-
symmetry twisted partition functions: The
torus twisted partition function characterizes the center-
vortex condensation, and the lens-space twisted partition function characterizes the monopole condensation. To justify our proposal, we study how these twisted partition functions behave in the adjoint
Higgs phase and show that their leading nontrivial contributions come from the center
vortex and monopole, respectively. Using the techniques of topological field theories, we uncover the relation between the center-
vortex and monopole condensations, and in particular, we prove that the gapped phase with the center-
vortex condensation necessarily shows the monopole condensation, too. We then study a center-
vortex model with monopoles as an illustrative example, and the higher-charge monopole condensation gives an example of the
symmetry fractionalization, which goes beyond the conventional Wilson-'t Hooft classification.
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Superconductivity
AC-flux-driven SQUID diode spectroscopy as a probe of current-phase relations
Yuriy Yerin, Iman Askerzade, Alexey Fedorchenko et al. (+2 more)
The current-phase relation (CPR) of a Josephson junction encodes microscopic information on superconducting states through higher-order and fractional harmonics. However, their unambiguous extraction is challenging, as different CPR components produce nearly identical static interference patterns that are further obscured by device asymmetries, damping, and dynamical effects. Here, we propose probing individual CPR harmonics via the ac
magnetic-flux-driven diode effect in asymmetric dc SQUIDs with unequal junction critical currents. Using two complementary reductions of the fast-driven dynamics – a Kapitza-type perturbation theory for the conventional junction and a Jacobi–Anger averaging for a general CPR – we show that ac flux modulation dresses each harmonic with a distinct Bessel function, yielding characteristic signatures in the diode efficiency $\eta(\phi_{\rm ac},\omega)$ as a function of ac flux amplitude $\phi_{\rm ac}$ and frequency $\omega$. We verify and extend these predictions by numerical solutions of the coupled dynamical equations for CPRs containing $\sin\varphi$, $\sin(\varphi/2)$, and $\sin 2\varphi$ terms ($\varphi$: superconducting phase difference), and construct phase diagrams of $\eta(\phi_{\rm ac},\omega)$. Distinct CPR components are revealed to produce characteristic weak, sparse, dense, or intermodulated arc patterns that remain robust in both overdamped and underdamped regimes. This suggests ac-flux-driven SQUID diode spectroscopy as a probe of current-phase relations in topological materials, multiband systems, and other unconventional
superconductors.
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All authors Yuriy Yerin, Iman Askerzade, Alexey Fedorchenko, Ali Gencer, Oleksandr Dobrovolskiy
Soft Condensed Matter
Using fast-reactive crosslinkers to modulate the internal structure of thermoresponsive microgels
Ballin Elisa, Brasili Francesco, Sztucki Michael et al. (+3 more)
The internal architecture of poly(N-isopropylacrylamide) (PNIPAM) microgels, which switches from fuzzy-sphere to
star-like when the standard N,N'-methylenebis(acrylamide) (BIS) crosslinker is replaced with ethylene glycol dimethacrylate (EGDMA), critically determines their interactions and swelling behavior. Here, we systematically investigate the role of the surfactant and crosslinker content in modulating the internal structure of the microgels using Dynamic Light Scattering, Small-angle X-ray Scattering and monomer-resolved numerical simulations. We reveal that the presence of the surfactant is crucial for obtaining the
star-like architecture, and that the transition from the
star-like regime to a more core-dominated structure occurs above a threshold EGDMA concentration. Monomer-resolved simulations capture how the role of surfactant differs between EGDMA-crosslinked and BIS-crosslinked microgels. Our findings establish a direct synthesis-structure relationship, providing a clear guidance for the rational design of soft,
star-like microgels with ultra-soft interactions, strenghtening the connection between microgels and model
star polymers.
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All authors Ballin Elisa, Brasili Francesco, Sztucki Michael, Rovigatti Lorenzo, Sennato Simona, Zaccarelli Emanuela
Soft Condensed Matter · Cross-listed from physics.optics
Multipolar optical binding in focus
Ashutosh Shukla, Sneha Boby and G V Pavan Kumar
The optical binding of gold nanoparticles has conventionally been explored within the Rayleigh limit using dipole approximations. But the field is increasingly focusing on the Mie regime for particles in the 100-500 nm range, where the dipole approximation is insufficient, and a complex landscape of multipolar resonances must be considered. This can be leveraged to engineer more complex forms of optical matter. To this end, we computationally study the optical binding force landscapes experienced by a pair of AuNPs using generalized multiparticle Mie theory. We calculate the total optical binding forces and mechanical trap stiffness values ($dF_i/di$) at the specific resonance wavelengths where the electric dipole, quadrupole, or octupole modes reach their respective scattering peaks and dominate the mechanical response. We demonstrate that the plasmonic mode
symmetry greatly influences the spatial distribution of zero-force nodes and the
rigidity of the optically bound dimer. By aligning these multipolar phenomena with standard experimental configurations, this work provides a mechanical framework for programmable metafluids and reconfigurable micromachines, bridging the gap between fundamental electrodynamics and reconfigurable nanomanipulation.
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Statistical Mechanics
First-order phase transitions in the three-dimensional Blume-Capel ferromagnet
D. Mataragkas, A. Vasilopoulos, Z.D. Vatansever et al. (+3 more)
We investigate first-order phase transitions in the three-dimensional Blume-Capel ferromagnet on the simple cubic
lattice by combining multicanonical simulations with two-parameter Wang-Landau sampling. The generalized-ensemble approach enables a detailed characterization of the coexistence region over a broad range of temperatures and
crystal-field couplings, extending from the vicinity of the tricritical point deep into the first-order regime. We analyze the finite-size scaling behavior of thermodynamic observables, with particular emphasis on the energy probability density function, free-energy barriers, and interfacial properties. The
evolution of the double-peaked energy distributions reveals a gradual crossover from weak to strong first-order behavior as the temperature is lowered. From the scaling of the free-energy barrier we determine the interface tension along the coexistence line and characterize its approach to the tricritical region through its vanishing behavior. In parallel, a field-mixing analysis based on the joint density of states obtained from two-parameter Wang-Landau simulations is employed to locate first-order transition points and probe tricritical behavior. While this approach has been highly successful in two-dimensional realizations of the Blume-Capel model, we find that in three dimensions its practical implementation becomes increasingly sensitive in the vicinity of the tricritical region, where the shallow structure of the relevant scaling variable distribution limits the ability to resolve coexistence conditions for the system sizes currently accessible. These results delineate the range of applicability of the method in three dimensions and provide a consistent picture of the first-order regime of the model.
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All authors D. Mataragkas, A. Vasilopoulos, Z.D. Vatansever, Y. Kim, D.-H. Kim, N.G Fytas
Mesoscale and Nanoscale Physics · Cross-listed from math-ph
Semiclassical Analysis of Tunneling in Graphene under Nonuniform Electrostatic and Magnetic Fields
Maria V. Perel
We develop a semiclassical theory of tunnelling of Dirac
fermions through an n-p-n junction in monolayer
graphene subjected to a perpendicular
magnetic field. Electrostatic and
magnetic fields are assumed to be smooth functions of a single spatial coordinate, supported on a finite interval, vanishing outside it, and thus ensuring asymptotically free states. In contrast to earlier studies restricted to constant
magnetic fields and exactly solvable electrostatic potential profiles, we consider a general electrostatic potential forming an n-p-n junction and an arbitrary
magnetic field, and formulate the corresponding scattering problem. Within the semiclassical approximation, and under an additional assumption on the incidence angle, the problem reduces to a connection problem for a pair of degeneracy points, treated using results from our earlier work. We obtain explicit expressions for the reflection and transmission coefficients, including their phases, as functions of energy and incidence angle. Furthermore, we derive semiclassical conditions for Fabry-Pérot resonances and "magic" angles, and analyse the resulting interference pattern. Numerical results demonstrate the angular dependence of transmission induced by the
magnetic field.
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Materials Science
Surface Induced Magnetism of CdSe Quantum Dots: A DFT Study
G. Kurian, D. Subedi, A. Aniagboso et al. (+1 more)
Surface induced magnetism of
quantum dots is not well understood and has been a subject of considerable controversy because of the complexity of surface chemistry of
quantum dot facets coupled with the many degrees of freedom inherently involved in magnetism. We performed
spin-polarized colinear density functional theory calculations to study charge and
spin densities to determine surface reconstructions in bare as well as passivated
quantum dots in controlled way. We find that tricoordinated surface atoms relax contributing no dangling bonds and bi-coordinated atoms dimerize, reducing the population of the dangling bonds affecting the induced magnetism. As a result, bicoordinated rather than tricoordinated surface atoms are responsible for
spin polarized surface states. In light of recent advanced experimental tools, we predict dangling bonds that remain, despite passivation, on low index facets with bicoordinated atoms could result in tunable surface magnetism. Our results also shed light on the contradicting experimental results in the literature.
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All authors G. Kurian, D. Subedi, A. Aniagboso, M. D. Mochena
Superconductivity
Graphene Josephson diodes from inherent asymmetric disorder
Ivan Villani, Luca Chirolli, Matteo Carrega et al. (+10 more)
Josephson diodes are non-reciprocal superconducting devices characterized by different switching currents depending on the current flow direction. They recently attracted considerable theoretical and experimental
attention, in view of their possible application as rectifying elements in the field of superconducting electronics, and as probes to investigate
symmetry breaking mechanisms in mesoscopic systems. In this work, we show that
graphene Josephson junctions provide rectification of supercurrent with an efficiency exceeding 20%. The effect appears applying a mT out-of-plane
magnetic field and is enhanced close to the nodes of the Fraunhofer interference pattern. Our theoretical model identifies long-range scattering potentials in the junction as the
symmetry-breaking mechanism, which yields supercurrent rectification in highly transparent junctions. While
graphene stands as an ultra-clean transmission medium, our work shows that unavoidable residual disorder in a clean two-dimensional system is sufficient to promote this effect. Tailoring of the inversion (mirror)
symmetry breaking could be obtained via proper design of external gates.
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All authors Ivan Villani, Luca Chirolli, Matteo Carrega, Alessandro Crippa, Elia Strambini, Francesco Giazotto, Vaidotas Miseikis, Camilla Coletti, Fabio Beltram, Kenji Watanabe, Takashi Taniguchi, Stefan Heun, Sergio Pezzini
Strongly Correlated Electrons
Probing La-based nickelates with Ni 1$s$ core-level photoelectron spectroscopy
Daisuke Takegami, Naoki Ito, Koto Fujinuma et al. (+15 more)
We present a comparative Ni core level photoemission study of La$_3$Ni$_2$O$_7$, Nd$_3$Ni$_2$O$_7$, and LaNiO$_3$ using both the Ni $2p$ and the Ni $1s$. We address the challenges in analyzing the widely investigated Ni $2p$ spectra arising from the substantial overlap in energy of the Ni $2p$ with the La $3d$. We show that on the other hand the deep Ni $1s$ core level does provide a clean view on the intrinsic electronic excitations and we highlight its potential to resolve detailed differences in the electronic structure within the strongly correlated Ruddlesden-Popper series La$_{n+1}$Ni$_n$O$_{3n+1}$.
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All authors Daisuke Takegami, Naoki Ito, Koto Fujinuma, Masato Yoshimura, Grace A. Pan, Dan Ferenc Segedin, Qi Song, Hanjong Paik, Charles M. Brooks, Hanjie Guo, Alexander C. Komarek, Takanori Taniguchi, Masaki Fujita, Julia A. Mundy, Takashi Mizokawa, Liu Hao Tjeng, Berit H. Goodge, Atsushi Hariki
Materials Science
Ground-state properties of the $S=3/2$ anisotropic triangular lattice antiferromagnet Na$_3$Cr(PO$_4$)$_2$
A. Magar, Sebin J. Sebastian, Q.-P. Ding et al. (+4 more)
We report the
crystal structure and
magnetic properties of a $S=3/2$ anisotropic triangular
lattice compound Na$_3$Cr(PO$_4$)$_2$ employing single-
crystal and powder x-ray diffraction, magnetization, heat capacity, and $^{31}$P
nuclear magnetic resonance (NMR) experiments, supported by the band structure calculations.
Magnetic susceptibility exhibits a broad maximum around 3.5 K, indicating the presence of a short-range
antiferromagnetic order, typical of a low-dimensional
spin system. Magnetization and heat capacity manifest an
antiferromagnetic long-range ordering at around $T_{\rm N} \simeq 2.6$ K. This was further confirmed by the drastic NMR line broadening and a peak in the
nuclear spin-
lattice and
spin-
spin relaxation rates. The isothermal magnetization data exhibit a field-induced
spin-flop transition at around $\mu_0H_{\rm SF} \simeq 1.7$ T reminiscent of an anisotropic two-dimensional magnet, before saturating above $\mu_0H_{\rm sat} \simeq 4.5$ T. The saturation field was further upheld by the field-dependent NMR relaxation measurements at low temperatures. The $^{31}$P NMR spectral shape confirms the commensurate
antiferromagnetic nature of the ordering below $T_{\rm N}$. Ab initio calculations reveal a significant deformation of the triangular
spin lattice, resulting in triangles with two
antiferromagnetic couplings of similar strength and a much weaker coupling along the third side of the triangle.
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All authors A. Magar, Sebin J. Sebastian, Q.-P. Ding, Y. Skourski, A. A. Tsirlin, Y. Furukawa, R. Nath
Strongly Correlated Electrons · Cross-listed from hep-th
Imprints of dynamical phases in semiclassical entanglement entropy in 2D CFT
Parijat Dey, Semanti Dutta and Bobby Ezhuthachan
We study the time
evolution of semiclassical
entanglement entropy in a class of $sl(2,\mathbb{R})$ driven states in a large $c$ conformal field theory (CFT) in $1+1$ spacetime dimensions. Upon varying the parameters of the drive, we find that the
entanglement entropy exhibits the signature of the dynamical phases of the driven CFT. We further study the
holographic dual of this CFT where the excited states of a minimally coupled scalar in $AdS_3$ induce a backreaction that modifies the background geometry. We compute the back reacted geometry by solving Einstein's equation with the expectation value of the stress tensor in the coherent state as the source term. Subsequently, we calculate the time
evolution of the perturbed minimal area and the bulk
entanglement entropy at $O(G_N^0)$, up to the sub-leading order in short distance approximation. These results match the CFT
entanglement entropy in the boundary at $O(c^0)$, and serve as a nontrivial check of the Faulkner-Lewkowycz-Maldacena (FLM)
conjecture for the first
quantum correction of
holographic entanglement entropy. The details of the check has been provided in the accompanying ancillary notebook.
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Statistical Mechanics
Work Extraction via Backward Motion in Optimal Closed-Loop Stochastic Control
Luis Frieder Reinalter, Emanuele Panizon, Lokesh Muruga et al. (+1 more)
We experimentally realize finite-time feedback control in an overdamped colloidal system using real-time optical tweezers with in situ reinforcement learning (RL). By varying the protocol duration tf for displacing the optical trap between prescribed positions, the optimal strategies identified by RL reveal a crossover from deterministic dragging toward the target to feedback-assisted exploitation of thermal fluctuations, reducing and eventually overcoming the energetic cost. The resulting policies agree quantitatively with the exact optimal closed-loop solution. By extending the approach to spatially localized external forcing, we further show that RL can identify optimal feedback strategies in heterogeneous
stochastic environments where direct analytical control design is challenging.
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All authors Luis Frieder Reinalter, Emanuele Panizon, Lokesh Muruga, Clemens Bechinger
Mesoscale and Nanoscale Physics
Atomic-scale sensing of photoexcitation processes in electronically isolated molecules via atomic force microscopy
Lisanne Sellies, Thomas Buchner, Jinhui Guo et al. (+6 more)
Atomic-scale insights into light-matter interaction can be obtained using light-assisted scanning probe microscopy techniques. Recently, photoexcited charge carriers have been detected by means of scanning tunnelling microscopy, enabling the study of photo-induced charge transfer with atomic-scale spatial resolution. Here, we propose an approach based on atomic force microscopy (AFM), namely photoexcitation single-charge AFM (PE-AFM), to detect photoexcitation in single molecules adsorbed on non-conductive dielectric films. Synchronizing
laser pulses to the oscillation of the tip of an AFM enables the detection of electron tunnelling events that follow photoexcitation. We demonstrate the PE-AFM technique for individual copper phthalocyanine molecules and achieve photoexcitation-driven AFM contrast with ångström spatial resolution. The observed sub-molecular contrast suggests the involvement of a long-lived quadruplet excited state. When combined with the recently developed AFM excited-state spectroscopy including lifetime measurements, PE-AFM enables comprehensive characterization of electronic states involved in photoexcitation and subsequent intersystem crossing, establishing a powerful platform for investigating photophysical processes at the single-molecule level.
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All authors Lisanne Sellies, Thomas Buchner, Jinhui Guo, Sonja Bleher, Felix Giselbrecht, Clea Ruth, Andrea Donarini, Jascha Repp, Laerte L. Patera
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Helical Dirac Current with Local Coupling to a Chiral Potential
Ju Gao and Fang Shen
We show that a propagating electron wave in the lowest cylindrical channel carries a
spin-resolved helical conserved current, and connect this current texture to its local
chiral coupling. In a weakly relativistic positive-energy Dirac projection, the two sectors have the same azimuthally symmetric charge density and opposite circulation superposed on longitudinal flow, even though their nonrelativistic orbital harmonic is $l=0$. The current is radially distributed and extends into the evanescent tail. A scalar screw potential couples these modes through a derived vertex expressed by the
chiral current overlap, $\mathcal J_\chi$. Both spatial textures determine the coupling: the environmental radial profile weights the electronic circulation, while the screw harmonic selects correlated changes of
spin sector and longitudinal momentum. For a uniform static harmonic, elastic energy conservation makes the first-order
spin-flip amplitude vanish within the same transverse mode. Environmental energy exchange is therefore required to activate these selected channels. The same current overlap supplies the spatial kernel for heliciton-assisted inelastic scattering in a companion study and for a subsequent transport treatment of chirality-induced
spin selectivity (CISS).
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Soft Condensed Matter
Defect Localization by Vanishing Deviatoric Stress in Active Nematics
Sameer Kumar and Manas Khan
Collective stress generation in cellular monolayers is a key phenomenological process governing coordinated migration and emergent multicellular dynamics. We employ a generic active nematics model to investigate stress generation and its associated properties. By analyzing the maximal principal stress and its correlation with the nematic director across different activity strengths, we find that the principal stress aligns perpendicular (parallel) to the nematic director for extensile (contractile) activity. In the turbulent regime, we identify a rotation-invariant scalar measure of the in-plane deviatoric stress whose zero-level contour coincides with the locations of all $\pm 1/2$ topological defects (both nematic and principal stress defects) are localized. This feature is robust and remains unchanged with variations in both the magnitude and nature (extensile or contractile) of activity. Our findings thus open up a new route to probe the spatial
alignment from the mechanical and rheological properties of confluent
cell layers, where stress measurements are more accessible than detailed
cell shape or size characterisation.
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Statistical Mechanics
Brownian gyration of an inertial ellipsoid
Soham Dutta and Arnab Saha
Recent studies on Brownian gyration (BG) have focused primarily on spherically symmetric particles under overdamped conditions. To explore BG in the underdamped regime with a spherically asymmetric particle, we investigate the inertial dynamics of a microscopic ellipsoid in a dissipative medium. The particle is confined in a spherically asymmetric trap and simultaneously coupled to two distinct thermal reservoirs. This configuration drives the system into a nonequilibrium steady state (NESS) characterised by BG, which is quantified by the mean and fluctuation of the particle's specific angular momentum. Using inertial Langevin dynamics, we systematically analyze how this microscopic gyration depends not merely on the trap asymmetry and temperature difference, but also on the particle's intrinsic physical properties like shape and axial orientation, besides inertia. Our study uncovers fundamental differences between the gyration of spherical and non-spherical particles in overdamped as well as underdamped conditions, at microscopic scales. These findings provide key insights for optimizing Brownian gyration across a broader landscape of experimentally tuneable parameters.
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Mesoscale and Nanoscale Physics
Beyond the interface: Persistent Hopping Transport and Frequency Dispersion in Strong-inversion Cryogenic MOSFETs
Keito Yoshinaga, Wataru Miyagi, Ryo Toyoshima et al. (+2 more)
Cryogenic complementary metal-
oxide-
semiconductor (cryo-CMOS) technology is essential for
quantum computing interfaces, which require precise modeling of dynamic device behavior. The output impedance of MOS field-effect transistors (MOSFETs) is frequency dependent, which has been conventionally attributed to extrinsic parasitics. Here, we report an intrinsic frequency dispersion in the channel impedance of cryogenic MOSFETs that persists deep into the strong-inversion region. Through a Cole-Cole analysis, we characterize this dispersion as a depressed semicircle in the impedance plane and attribute its behavior to variable-range hopping through band-tail localized states. Unlike conventional models where band-tail states are confined to the
oxide interface, we demonstrate that in MOSFETs with high channel doping the band-tail states are induced by ionized
impurities and distributed throughout the depletion region. Our paradigm accounts for frequency dispersion under strong inversion. This work demonstrates that ionized-
impurities-induced hopping governs the dynamic response of cryo-MOSFETs channel impedance even when drift conduction dominates, offering critical insights for accurate small-signal modeling and high-frequency cryo-CMOS
circuit design.
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All authors Keito Yoshinaga, Wataru Miyagi, Ryo Toyoshima, Munehiro Tada, Ken Uchida
Mesoscale and Nanoscale Physics
Anomalous Pairing Currents and a Second Topological Edge Channel in Bosonic Lattices
Chitrak Bhadra, Ángel Rivas and Miguel A. Martin-Delgado
We show that bosonic pairing opens a second
chiral current channel on a 2D kagome
lattice, absent from any particle-conserving model. From the continuity equation, we derive both a hopping current and an anomalous pairing current on the
lattice, and predict
chiral circulation in bulk-gapped phases with integer para-
unitary Chern numbers, as well as a phase-sensitive leakage ratio, $\Lambda_{\cal I}$, for the pairing current around a defect. This ratio can be tuned from confined to strongly anomalous regimes at fixed
topology. The two channels differ microscopically: the hopping current is sourced by the on-bond single-particle coherence, whereas the pairing current is sourced by the off-site anomalous coherence, whose spatial range is governed by the BdG pairing gap rather than by the single-particle gap. This separation produces distinct defect-induced signatures in real space, identifies a regime in which bulk
topology and anomalous edge response coexist with no analogue in particle-conserving matter, and is directly testable in driven photonic
lattices and superconducting-
circuit arrays.
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Strongly Correlated Electrons
Flat-Band Stoner Instability and Peierls-Phase Origin of the Transdimensional Anomalous Hall Effect in Rhombohedral Graphite
Yang Zhou
A “transdimensional” anomalous
Hall effect (TDAHE), where both in-plane ($\Bpar$) and out-of-plane
magnetic fields produce hysteretic
Hall signals, was recently observed in nine-layer rhombohedral graphite~\cite{Li2026Nature}. We present a microscopic theory attributing the TDAHE to a flat-band Stoner instability coupled to Peierls-phase gap modulation. The flat-band density of states satisfies the Stoner criterion $U\rho(\varepsilon_F) > 1$~\cite{Bultinck2020}, driving a
spin-valley-locked ferromagnet whose valley polarization $\eta$ breaks time-reversal
symmetry and generates an intrinsic anomalous
Hall conductivity (AHC). The orbital $g$-factor $g_{\mathrm{orb}} = e d_0 v_F (N{-}1)/2 \propto (N{-}1)$ then lets $\Bpar$ modulate the gap, producing the transdimensional response $\propto \eta$. A self-consistent $2N$-band Hartree-Fock calculation yields complete valley polarization ($\eta \to 1$) below a mean-field transition $T_c^{\mathrm{MF}} \approx 2.2$~K, reduced by 2D-Ising critical fluctuations to the experimental $T_c \approx 1.6$~K, with $R_{xy} \approx 1.5$~k$\Omega$. Because both
Hall responses are carried by one order parameter $\eta$, they share a single $T_c$, as observed; $T_c$ is governed by the Stoner product $U\rho$ and is insensitive to the intervalley exchange, which only gates whether the valley-polarized phase forms, so the exchange strength is not a fitted parameter. Beyond reproducing $R_{xy}$, $T_c$, and the phase window, the theory predicts a sharp onset of valley polarization between $N = 7$ and $N = 9$, a
symmetry selection rule fixing the crescent
Fermi surface to the $m{=}1$ nematic channel, and a transdimensional-to-conventional
Hall ratio $\sigmaPHE/\sigmaAHE^{\mathrm{tot}} = g_{\mathrm{orb}}\Bpar/m$ independent of $\eta$ and $U$. The $Z$-independence of the intrinsic AHC is verified within dynamical mean-field theory.
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Disordered Systems and Neural Networks
Hyperuniform charge distributions and phase transitions in a generalized Aubry-André model
Lujia Xiang, Junmo Jeon and Shiro Sakai
We show the existence of distinct inhomogeneous charge distributions and a phase transition between them in aperiodic
fermion systems. Using a generalized Aubry-André model as an example, we obtain various types of charge distributions, which we classify by means of hyperuniformity, a general mean to quantify and classify the global uniformity of spatial distributions. Examining various cases of filling fraction and potential strength and shape, we find that the many-body charge distribution in this model is always hyperuniform, i.e., showing an anomalously suppressed long-range fluctuation, while its hyperuniformity class depends on the localization properties of the states around the
Fermi energy, irrespective of those of high-energy states. Namely, the change in the localization properties of these single-particle states leaves a signature in the hyperuniformity class of many-body charge distribution. We further show a change of the hyperuniformity class corresponds to a phase transition between inhomogeneous many-body states, and that it is of the third order.
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Materials Science
Hybrid Electronic-Ionic Ferroelectricity in Superlubric van der Waals Heterostructures
Jing Huang, Jun Kang and Daniel Bennett
One strategy to lower the switching barrier in a sliding ferroelectric (sFE) is to insert an incommensurate spacer to reduce sliding friction, creating a superlubric sliding ferroelectric (SL-sFE). However, how polarization survives across the effectively decoupled outer layers remains an open question. We show that SL-sFEs are fundamentally different from conventional sFEs: polarization is not driven by sliding alone, but by an intricate coupling between interlayer sliding and the out-of-plane buckling of the spacer layer. This coupling results in a unique hybrid electronic-ionic polarization arising from asymmetric orbital hybridization. The interplay of these order parameters generates several distinct types of ferroelectric hysteresis, including mixed first- and second-order transitions, multi-step switching, and antiferroelectric-like behavior, establishing SL-sFEs as a distinct class of ferroelectrics.
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Superconductivity
Distinguishing Majorana zero modes from trivial defect states in an iron-based superconductor
Dongfei Wang, Jon Ortuzar, Freek Massee et al. (+5 more)
Majorana zero modes, which obey non-Abelian exchange statistics, are promising candidates for topological
quantum computation due to their robustness against environmental perturbations. The iron-based
superconductor Fe(Te,Se) has been identified as an intrinsic topological
superconductor, possibly hosting Majorana zero modes. In this paper, we report the observation of near-zero-energy localized states at multiple structural defects on the Fe(Te,Se) surface, which could be misidentified as Majorana zero modes without additional verification. By using
spin-polarized scanning tunneling spectroscopy, we demonstrate that the near-zero-energy localized states on step edges and line defects originate from topologically trivial Yu-Shiba-Rusinov states. In addition, zero-energy bound states are also observed for regions without surface defects. A combined spatial and
magnetic field dependent analysis of the
spin-resolved tunneling spectra in these regions reveals that this type of zero-energy states cannot be attributed to the presence of Majorana bound states. These findings emphasize the importance of
spin-dependent studies of low-energy states for pursuing Majorana zero modes.
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All authors Dongfei Wang, Jon Ortuzar, Freek Massee, Ruidan Zhong, Genda Gu, Wende Xiao, Yugui Yao, Roland Wiesendanger
Quantum Gases
Vorticity Induced by Non-frontal Collisions of Quantum Droplets
J. E. Alba-Arroyo, Santiago F. Caballero-Benitez and Rocio Jáuregui
The rotational dynamics induced by the non-frontal binary collisions of
quantum droplets composed of ultracold alkali atoms are analyzed. A theoretical study is presented within the extended Gross-Pitaevskii equation framework, using experimentally feasible conditions. Numerical experiments elucidate a rich landscape of possible topological excitations in the system that are robust towards measurements. The collision of heteronuclear
quantum droplets composed of $^{41}$K and $^{87}$Rb atoms in the incompressible regime gives rise to dynamical instabilities that spontaneously generate topological defects:
vortex rings, dislocation lines, and
vortices in one species. Their presence depends on the Weber number and the impact parameter. An experimental proposal for
vortex detection in both real and
Fourier space using interaction ramps is described.
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Materials Science
Lifetime Sample Tracking (LiST): A Data Platform for Materials Science
Anthony Richardella, Isaiah A Moses, Konrad Hilse et al. (+9 more)
The 2D
Crystal Consortium Materials Innovation Platform (2DCC-MIP) is an NSF supported national user facility focused on advancing the synthesis of 2D materials, monolayers, surfaces, and interfaces. The need for the facility to organize and share data with users led to the development of an internal data management and analysis engine, the Lifetime Sample Tracking platform (LiST). This infrastructure allows the automated capture, curation, analysis and dissemination of data ranging from experimental materials synthesis parameters and characterization, to theoretical first-principles and ReaxFF molecular dynamics modeling1. The system currently hosts synthesis and property data (accessible via a REST API) on approximately twenty thousand samples produced by the 2DCC grown using a variety of techniques from bulk
crystal growth to metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE), among others. Data used in publications can easily be grouped by the system into data packages that are given digital object identifiers (DOIs) for inclusion with each publication. The LiST platform is now being used by groups outside of the 2DCC as a solution for data curation in materials science. Data management tools such as LiST support the materials development process by allowing a closed loop iteration between synthesis, characterization, theory, and targeted materials design. This also enables machine learning (ML) research, artificial intelligence (AI) analysis, and the potential for autonomous synthesis in the future.
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All authors Anthony Richardella, Isaiah A Moses, Konrad Hilse, Frank Santaguida, Kevin Dressler, Ric Wilburn, Saiyyam Kochar, Wesley F. Reinhart, Adri C. T. van Duin, Nitin Samarth, Vincent H. Crespi, Joan M. Redwing
Materials Science · Cross-listed from cs.LG
Toward Controllable Catalyst Inverse Design via Large-Scale Autoregressive Pretraining
Dong Hyeon Mok, Jonggeol Na and Seoin Back
Inverse design of heterogeneous catalysts remains challenging because catalyst surfaces exhibit substantial structural complexity with coupled surface-adsorbate interactions across a vast chemical space that is difficult to explore efficiently through conventional screening alone. Although machine learning-based high-throughput screening has accelerated catalyst discovery, its efficiency inevitably declines as the search space grows, motivating the development of generative models that can directly construct catalysts with target properties. Here, we present a conditional catalyst generative model based on the Generative Pretrained
Transformer architecture with a numerical
embedding layer that enables the generation of catalyst structures conditioned on both categorical and continuous properties within a single autoregressive framework. The model was pretrained on 133 million catalyst structures and subsequently fine-tuned on approximately 460,000 optimized structures with associated categorical properties and binding energies for conditional generation. The resulting model achieved 98% structural validity, 95% optimization validity, and high categorical condition fidelity, with a 93 % joint match rate for adsorbate type and composition. For binding energy conditioning, the match rate of approximately 20% represents a four-fold improvement over the baseline training distribution, and the generated distributions shift systematically toward the target values, enabling a 1.5 to 4-fold improvement in screening efficiency for reaction-targeted catalyst discovery without additional fine-tuning. These results show that large-scale autoregressive pre-training, combined with explicit property conditioning, provides a practical route toward controllable catalyst generation and accelerated catalysts discovery.
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Materials Science
Coexistence of Donor and Acceptor Hydrogen States in n-Type InN
Masaki Kobayashi, Yudai Yamashita, Kazuyuki Hirama et al. (+1 more)
Hydrogen often exhibits amphoteric behavior in
semiconductors, but its role is in n-type InN remains unresolved. Wurtzite InN is a narrow-gap
semiconductor with high electron mobility and is therefore attractive for high-speed electronics and optoelectronic applications. Here we use hard x-ray photoemission spectroscopy (HAXPES) to probe hydrogen-related electronic structure in as-grown and post-annealed InN thin films prepared at different grown temperatures. Post annealing, which reduces the concentration of hydrogen
impurities in the films, shifts the core-level spectra toward lower binding energy, consistent with a chemical-potential shift associated with the passivation of electron carriers. In the valence-band spectra, an acceptor-like in-gap feature near the valence-band maximum is suppressed after annealing. Together with the established donor-like behavior of hydrogen in InN, these results suggest that acceptor H- states coexist with donor H+ states in InN. The coexistence of these opposite hydrogen charge states provides a microscopic picture of hydrogen-driven compensation in InN and highlights the amphoteric nature of hydrogen even in a highly n-type
semiconductor.
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All authors Masaki Kobayashi, Yudai Yamashita, Kazuyuki Hirama, Yoshitaka Taniyasu
Mesoscale and Nanoscale Physics
Surface-switchable nonreciprocity protected by Fermi arcs in Weyl semimetal TaAs
Dong Li, Yuki M. Itahashi, Ying-Ming Xie et al. (+12 more)
Weyl semimetals host topologically protected surface states, known as
Fermi arcs, which connect bulk Weyl nodes in momentum space. Both bulk Weyl nodes and
Fermi arcs are anticipated to be
chiral. The chirality of bulk bands has been confirmed through observations of the
chiral anomaly and Weyl orbits. In contrast, despite their discovery more than a decade ago, the
chiral nature of
Fermi arcs has remained unresolved. Here we report
Fermi-arc-induced nonlinear transport in the archetypal Weyl semimetal TaAs. Using focused ion beam techniques, we fabricated micro-scale devices that enable simultaneous transport measurements on opposing topological surfaces. While linear transport remains dominated by bulk conduction, nonlinear transport uncovers surface-specific contributions, including an exceptionally large third-order nonreciprocal response that exceeds conventional expectations and highlights the crucial role of the singular arc endpoints. Our findings unambiguously demonstrate the
chiral nature of
Fermi arcs and establish nonlinear transport as a direct probe of these topological surface states. By revealing a surface-switchable, room-temperature nonlinear response that is topologically protected, this work introduces a new functionality in Weyl semimetals. Given the abundance of natural materials predicted to host topological semimetal states, these results open opportunities for exploring nonlinear transport phenomena and device concepts across a broad class of systems.
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All authors Dong Li, Yuki M. Itahashi, Ying-Ming Xie, Menghu Zhou, Yukako Fujishiro, Kunjie Zheng, Yao Guang, Max T. Birch, Ilya Belopolski, Max Hirschberger, Takahiro Morimoto, Xiao-Xiao Zhang, Zhi-An Ren, Naoto Nagaosa, Yoshihiro Iwasa
Mesoscale and Nanoscale Physics
Dispersive mode coupling in $p$-doped semiconductor nanomechanical resonators
Ankang Liu, Mahmoud T. Elewa and Mark I. Dykman
Dispersive coupling between vibrational modes with different frequencies is a major nonlinear dynamical effect. We show that in $p$-doped
semiconductors such coupling is strongly enhanced. Moreover, the coupling parameters increase with the order of the nonlinearity. The doping-induced dispersive coupling becomes much stronger than the intrinsic one already for moderately strong doping. Its dependence on the hole density is nonmonotonic, and the temperature dependence becomes nonmonotonic for higher densities. Relevant mesoscopic frequency fluctuations are briefly discussed. The results are applied to Si resonators, where doping is used to compensate the temperature dependence of a clock mode, whereas another low-frequency mode is used as a thermometer to enable temperature stabilization.
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