Mesoscale and Nanoscale Physics
Observation of microscopic domain effects in the metal-insulator transition of thin-film NdNiO$_3$
Lucy S. Nathwani, Anne Ruperto, Ashvini Vallipuram et al. (+8 more)
Perovskite
oxides display correlated electrical,
magnetic, and thermal properties that can be further tuned in the thin-film limit, making them contenders for next-generation electronics. Measuring thermal transport in thin films is challenging, because traditional techniques are dominated by the substrate. Here, frequency-domain thermoreflectance (FDTR) of an epitaxial NdNiO$_3$ thin film reveals a sharp change in out-of-plane thermal conductivity across the metal-
insulator transition. Complementary frequency-domain photoreflectance (FDPR) reveals a large change in ambipolar diffusivity of photoexcited carriers. While the in-plane electrical resistance shows large hysteresis, out-of-plane thermal and charge transport shows negligible hysteresis. We attribute this discrepancy to anisotropy in the percolation of nanoscale domains across the transition as the film thickness approaches the domain length scale. We establish FDTR and FDPR as sensitive probes of
quantum material phase transitions and highlight NdNiO$_3$ for thermal control and
memory applications.
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All authors Lucy S. Nathwani, Anne Ruperto, Ashvini Vallipuram, Abigail Y. Jiang, Grace A. Pan, Dan Ferenc Segedin, Ari B. Turkiewicz, Charles M. Brooks, Jarad A. Mason, Qichen Song, Julia A. Mundy
Quantum Gases
Heterosymmetric states of rotating quantum droplets under confinement
S. Nikolaou, G. M. Kavoulakis and M. Ogren
We investigate the rotational response of a confined, two-dimensional
quantum droplet, which emerges in an attractive binary Bose mixture that is stabilized against collapse by beyond-mean-field effects. We consider both a harmonic and an anharmonic form for the external confining potential. We go beyond the widely employed “phase-locked" single-order-parameter model, maintaining two separate order parameters for the two components, and calculating the lowest-energy state for various values of the angular momentum. For a population-balanced
quantum droplet and sufficiently tight confinement, we find that near certain half-integer values of the angular momentum the droplet is excited in a “heterosymmetric" manner, with the two components carrying different vorticities. This mode is naturally missed by the single-order-parameter model. We additionally investigate the effects of a small population imbalance in the droplet. Apart from an energy increase associated with the population difference, the imbalance also lifts the double degeneracy of the heterosymmetric states, which characterizes the $\mathbb{Z}_2$-symmetric balanced droplet. The heterosymmetric mode is found to be favored by the energy term which captures the beyond-mean-field effects in the mixture.
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Statistical Mechanics · Cross-listed from math.PR
A Constructive Approach to $q$-Gaussian Distributions: $\alpha$-Divergence as Rate Function and Generalized de Moivre-Laplace Theorem
Hiroki Suyari and Antonio M. Scarfone
The Large Deviation Principle (LDP) and the Central Limit
Theorem (CLT) are central pillars of probability theory. While their formulations are established under the i.i.d. assumption, the probabilistic foundation for power-law distributions has primarily evolved through descriptive models or variational principles, rather than a constructive derivation comparable to the classical binomial process. This paper establishes a constructive probabilistic framework for power-law distributions, proceeding from the nonlinear differential equation $dy/dx = y^q$ without assuming a specific distribution a priori. We build the algebraic and combinatorial foundations, which lead to a generalized binomial distribution based on finite counting. We prove the LDP for this generalized binomial distribution in the regime $0 < q < 1$, demonstrating that the $\alpha$-divergence is identified as the rate function, and clarify the breakdown of this macroscopic scaling for heavier tails ($q > 1$). This result connects our constructive framework to the structures of information geometry. Furthermore, we prove a generalized de Moivre-Laplace
theorem, showing that the generalized binomial distribution converges to a heavy-tailed limit distribution (the $q$-Gaussian distribution). We derive that the scaling law follows the order of $n^{q/2}$ as a consequence of the underlying nonlinearity. These analytical results are numerically verified for distinct values of $q \in (0, 2)$. This framework provides a constructive basis that unifies the shift-invariant exponential family and the rescaling-invariant power-law family.
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Quantum Gases · Cross-listed from physics.optics
Universal exciton polariton logic gates in Ouroboros rings
Tobias Schneider, Stefan Schumacher and Xuekai Ma
All-optical logic gates have significantly advanced over a diverse range of photonic systems, boosted by intricate nonlinearities that facilitate the engineering of complex logic operations. Here, we demonstrate that in
semiconductor microcavities, polariton condensates trapped in Ouroboros-shaped rings form specifically charged
vortices, determined by the strength of nonlinearity and the excitation method. Quantized
vortex phases encode binary digits that can be nonresonantly controlled by optical pulses incident directly upon the ring, enabling logic operations. By interconnecting three polariton Ouroboros rings, we realize a universal set of logic gates (AND, OR, NIMPLY) fundamental to functional polaritonic devices. The Ouroboros structures are highly customizable, providing a robust and promising platform for exploring more complex logic operations.
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Disordered Systems and Neural Networks
Signatures of Nonergodicity in Sparse Random Matrices
Sagnik Seth, Adway Kumar Das and Anandamohan Ghosh
The prevalence of sparsity in the Fock space graph of interacting many-body systems motivates an investigation into the spectral statistics of sparse random
matrices with on-site disorder. We numerically determine the delocalization-localization transition in the ground state as a function of the sparsity. The short-range energy correlation in the bulk indicates that the Anderson transition at infinite temperature occurs at the critical percolation limit of the sparse graph. By analytically deriving the energy moments and calculating the shifted kurtosis, we show that the critical sparsity threshold matches the Anderson transition. Furthermore, long-range energy correlations in the bulk spectrum reveal a Thouless energy scale, suggesting a broad nonergodic regime within the delocalized phase.
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Mesoscale and Nanoscale Physics
Joule heating and electronic Gurzhi effect in hydrodynamic differential transport in an electron liquid
Yi Wang, Shu-Yu Zheng, Li Lu et al. (+2 more)
We perform a differential resistance study in the hydrodynamic regime of electron
liquid in GaAs/AlGaAs
quantum wells. At zero
magnetic field ($B$) a Lorentzian profile occurs in the nonlinear transport driven by a U-turn (ac) current loop, in (ac + dc) measurements a minimum deepens with the external dc current bias ($j_{dc}$). Our analysis shows that the observed electronic transport valley induced by $j_{dc}$ is attributed to Joule heating effect on the electron temperature ($T_{e}$) of electron
liquid. Quantitatively, we demonstrate that the viscosity resistivity ($\Delta \rho$) is proportional to $T^{-2}$ and is consistent with the dc-current induced electronic Gurzhi effect in various configurations of measurement.
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All authors Yi Wang, Shu-Yu Zheng, Li Lu, Kai Chang, Chi Zhang
Soft Condensed Matter
Deformed states in paraelectric and ferroelectric nematic liquid crystals
Oleg D. Lavrentovich
Ground states of materials with orientational order ranging from solid ferromagnets and ferroelectrics to
liquid crystals often contain spatially varying vector-like order parameter caused by inner factors such as the shape of building units or by the geometry of confinement. This review presents examples of how the shapes, chirality, and polarity of molecules and spatial confinement induce deformed
equilibrium and polydomain states with parity breaking, splay, bend, and twist-bend deformations of the order parameter in paraelectric and ferroelectric nematic
liquid crystals. Parity breaking results either from chirality of the constituent molecules, as a replacement of energetically costly splay and bend in paraelectric nematics, or in response to depolarization field in the ferroelectric nematic. Both paraelectric and ferroelectric nematics exhibit a splay cancellation effect, in which the elastic and electrostatic energies of splay along one direction are reduced by an additional splay along orthogonal directions.
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Statistical Mechanics
Taming of free volume in statistical mechanics of the hard disks model
Victor M. Pergamenshchik, Taras Bryk and Andrij Trokhymchuk
We turn the long time puzzle of the free volume, known for its highly irregular form, into exact analytical formulae and develop statistical mechanics of the hard disk model. The free volume is exactly expressed in terms of the intersection areas of up to five exclusion circles, which can be computed analytically as functions of disk coordinates. In turn, the free volume determines the partition function and
entropy. The partition function is shown to factorize into a product of free volumes and admits two exact limiting forms corresponding to gaslike and liquidlike regimes. From this construction, using Monte Carlo-generated disk coordinates, the
entropy and pressure are obtained analytically and recover the known equation of state of hard disks in almost entire density range up to the close packing. At intermediate densities, the theory reveals a mixed
liquid regime associated with defect formation preceding the hexagonal ordering. The intersection area of five disks emerges as a scalar measure of the local hexagonal order. The theory can be directly adopted for the hard sphere model.
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Strongly Correlated Electrons
Universally Diverging Grüneisen Ratio of Holographic Quantum Criticality
Jun-Kun Zhao, Enze Lv, Wei Li et al. (+1 more)
Quantum criticality is a hallmark of strongly correlated electron systems, as seen in heavy-
fermion materials and high-temperature
superconductors.
Holographic duality provides a powerful framework to investigate these systems by translating them into weakly coupled classical
gravity living in one higher dimension. Here, we harness this approach to study a field-induced
quantum critical point with dynamical exponent $z=3$ in Einstein-Maxwell-Chern-Simons theory. Our analysis of its thermodynamic properties reveals a new universality class. Notably, we identify a diverging Grüneisen ratio with universal scaling $\sim T^{-2/3}$, a behavior that closely mirrors recent experiments on the heavy-
fermion material CeRh$_6$Ge$_4$. These findings advance our understanding of metallic
quantum criticality and highlight the potential of
holographic duality as a tool for studying correlated
quantum matters.
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All authors Jun-Kun Zhao, Enze Lv, Wei Li, Li Li
Materials Science
Engineering magnetism in hybrid organic-inorganic metal halide perovskites
Yaiza Asensio, Lucía Olano-Vegas, Samuele Mattioni et al. (+4 more)
The chemical and structural flexibility of hybrid organic-inorganic metal halide perovskites (HOIPs) provides an ideal platform for engineering not only their well-studied optical properties, but also their
magnetic ones. In this review we present HOIPs from a new perspective, turning the
attention to their
magnetic properties and their potential as new class of on-demand low-dimensional
magnetic materials. Focusing on HOIPs containing transition metals, we comprehensively present the progress that has been made in preparing, understanding and exploring
magnetic HOIPs. First, we briefly introduce HOIPs in terms of composition and
crystal structure and examine the synthesis protocols commonly used to prepare those showing
magnetic properties. Then, we present their rich
magnetic behavior and phenomenology; discuss their origin and guidelines for tuning them by changing the perovskite phase, chemical composition and dimensionality; and showcase their potential application in magneto-optoelectronics and spintronics. Finally, we describe the current challenges in the field, such as their integration into devices, as well as the emerging possibilities of moving from
magnetic doping to pure transition metal-based HOIPs, which will motivate further studies in the future.
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All authors Yaiza Asensio, Lucía Olano-Vegas, Samuele Mattioni, Marco Gobbi, Fèlix Casanova, Luis E. Hueso, Beatriz Martín-García
Soft Condensed Matter
Non-Hermitian chiral surface waves in disordered odd solids
Cheng-Tai Lee and Tomer Markovich
Chiral surface waves are surface-localized modes that propagate unidirectionally along a boundary, enabling directed transport and minimal back-scattering. While first identified in
quantum systems, they were recently shown to emerge in classical metamaterials in the presence of `odd elasticity'. Owing to the non-reciprocality of odd elasticity, these waves exhibit growing amplitudes during propagation, reminiscent of the non-Hermitian skin effect. To date, studies of odd elastic systems have mainly focused on ordered structures. Whether structurally-disordered materials can host non-Hermitian
chiral surface waves (NHCSW) remains unexplored. We address this question using a minimal model of torque-driven disordered odd solids. Such solids are abundant, from biological gels such as the cytoskeleton driven by motor-
proteins to synthesized systems such as
magnetic colloidal gels. We find that torque-driven disordered odd solids have unique NHCSW with stronger surface localization and stable boundary velocity, in contrast to previous
lattice models of odd solids. These distinct features stem from an intrinsic interplay between boundary torques and odd elasticity in torque-driven odd solids. Our results offer a new strategy to control NHCSW using active torques.
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Statistical Mechanics
The phase boundary of the random site Ising model
Riccardo Ben Alì Zinati, Giacomo Gori and Alessandro Codello
We introduce a new approach to disordered two-dimensional Ising models based on the extension of the combinatorial solution to randomized supercells. Applying it to the site-diluted Ising model on the square
lattice, we resolve the full phase boundary $T_c(p)$ from the pure-Ising point to the percolation limit $T_c(p_c)=0$ with, in principle, arbitrary precision. The critical
eigenvalue governing the transition is found to follow a remarkably accurate linear interpolation between the Ising and percolation endpoints, whose small but systematic deviations reveal the nontrivial fine structure of the phase boundary. Near the percolation threshold, we confirm the crossover exponent $\phi_{\rm RSIM}=1$ and extract the nonuniversal amplitude ${\alpha_{\rm RSIM}\simeq 1.616}$.
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Strongly Correlated Electrons
Non-invertible symmetries and boundary conditions for the transverse-field Ising model
Huan-Qiang Zhou and Qian-Qian Shi
Non-invertible Kramers-Wannier (KW) duality
symmetries are constructed for the transverse-field Ising model (TFIM) at the self-dual point under various boundary conditions (BCs), as long as the resultant
Hamiltonian commutes with the ${\rm Z}_2$
symmetry operator. This is achieved by introducing extra degrees of freedom into the
Hilbert space, in order to turn a non-translation-invariant
Hamiltonian in the original
Hilbert space into a translation-invariant
Hamiltonian in the augmented
Hilbert space. One may lift the trivial identity operator, the ${\rm Z}_2$
symmetry operator and the non-invertible KW duality
symmetry operator to their counterparts in the augmented
Hilbert space, valid for each of four types of toroidal BCs. As it turns out, they yield a
lattice version of fusion rules, which bears a resemblance to the Tambara-Yamagami ${\rm Z}_2$ fusion category. Our construction is thus consistent with the basic physical requirement that all possible BCs should yield a converging result in the thermodynamic limit. In particular, the
lattice versions of fusion rules, constructed by Seiberg, Seifnashri and Shao [SciPost Phys. 16, 154 (2024)], are reproduced for periodic and anti-periodic BCs, but a discrepancy is revealed for duality-twisted BCs.
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Soft Condensed Matter
Disorder-induced persistent random motion and trapping of microswimmers
Mirko Residori, Sebastian Aland and Christina Kurzthaler
Microorganisms ofter move in confined, disordered environments, where hydrodynamic couplings can modify their transport behavior. Using extensive finite-element simulations, we investigate the dynamics of microswimmers – modeled as squirmers – in two-dimensional disordered porous media by resolving the full hydrodynamic interactions. We reveal that the deterministic coupling between activity, hydrodynamics, and disorder is sufficient to generate effective diffusive transport. Strong pushers and pullers become localised in the porous medium either by trapping at corners or dynamic trapping, depending on swimmer type and obstacle packing fraction. Squirmers can escape from dynamic traps, leading to a prominent “hopping-and–trapping” dynamics. Strikingly, we find a pusher-puller asymmetry in the trapping probability that can be reversed by short-range swimmer-obstacle interactions, highlighting the sensitivity of transport to near-field effects.
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Other Condensed Matter · Cross-listed from quant-ph
Gauge-Invariant Non-Hermitian Quantum Theory: Foundation and Applications to Dynamical Phase Transitions
Fei Wang, Guoying Liang, Zecheng Zhao et al. (+1 more)
The description of states and dynamics in non-Hermitian systems is fundamentally linked to the choice of an appropriate theoretical framework – a point of ongoing debate in the field. This work addresses this issue by proposing a consistent formulation that reconciles existing controversies and establishes a unified theoretical understanding. Our approach rests on two foundational premises: (i) the dynamics of both left and right-vectors of a non-Hermitian system must satisfy the Schrödinger equation; (ii) the theoretical framework must preserve gauge invariance, ensuring that physical quantities are independent of unobservable phase choices. Building on these physically motivated assumptions, we refine the biorthogonal framework, leading to a gauge-invariant non-Hermitian
quantum theory. Our framework naturally encompasses the open-system effective non-Hermitian
evolution as a special case, and can naturally reduce to standard
quantum mechanics in the Hermitian limit. As a concrete application, we analyze the dynamical phase transition in a one-dimensional Su-Schrieffer-Heeger (SSH) model within this gauge-invariant non-Hermitian
quantum theory. Notably, our formulation naturally generalizes the known condition for such transitions in Hermitian two-band systems, namely, $\mathbf{d}_{k}^i\cdot\mathbf{d}_{k}^f=0$, to the non-Hermitian case, where it takes the form $\mathrm{Re}\Bigl[\frac{\mathbf{d}_{k}^i}{d_{k}^i}\cdot\frac{\mathbf{d}_{k}^f}{d_{k}^f}\Bigr]=0$. Furthermore, we identify entirely new dynamical phase transitions that cannot be characterized by the winding number. We hope that this gauge-invariant non-Hermitian
quantum theory will find broad applications in the study of non-Hermitian systems.
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All authors Fei Wang, Guoying Liang, Zecheng Zhao, Bao-Ming Xu
Mesoscale and Nanoscale Physics
Phase-Space Quantum Geometry Beyond Adiabatic Electron Dynamics
Luca Maranzana, Koki Shinada, Ying-Ming Xie et al. (+2 more)
The geometry of electronic
quantum states plays an important role in the
equilibrium and transport properties of solids. While the Berry
curvature is known to influence electron motion, recent work has shown that the
quantum metric also affects the motion of electron wave packets beyond the adiabatic approximation. To connect this nonadiabatic dynamics to many-electron observables, we derive an equivalent semiclassical formulation, valid up to second order in $\hbar$. The resulting phase-space measure and kinetic equation incorporate the
quantum metric over the full phase space, including its mixed real-momentum components. We show that, in spatially inhomogeneous systems, the full phase-space
quantum metric contributes to electric polarization in
insulators and generates an intrinsic linear
Hall response in metals. As a concrete example, we study Dirac electrons subject to a
magnetic texture and a background potential that vary periodically in space. In this model, the mixed components of the phase-space metric produce a
Hall contribution controlled by the relative phase between the two modulations. This phase-sensitive response can remain finite even when the conventional anomalous
Hall conductivity vanishes. More broadly, our formulation enables the systematic study of
equilibrium and transport responses in systems whose
quantum geometry involves both position and momentum.
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All authors Luca Maranzana, Koki Shinada, Ying-Ming Xie, Sergey Artyukhin, Naoto Nagaosa
Materials Science
Disentangling Anomalous Hall Effect Mechanisms and Extra Symmetry Protection in Altermagnetic Systems
Yuansheng Bu, Ziyin Song, Zhong Fang et al. (+2 more)
We investigate the
evolution of Anomalous
Hall Conductivity (AHC) in a coplanar and collinear
antiferromagnetic system with varying
spin canting angles. A tight-binding model based on three t2g-orbitals in a body-centered tetragonal
lattice is constructed, where the inclusion of third-nearest neighbor hopping is demonstrated to be essential for capturing the characteristic energy band splitting of altermagnetic materials. By employing a
symmetry analysis based on
spin space groups and treating
spin-orbit coupling (SOC) as a perturbation, we theoretically distinguish and numerically verify two origins of the transverse transport: the conventional anomalous
Hall effect (AHE) induced by net magnetization and the
Crystal Hall Effect (CHE) arising from specific
crystal symmetries. Our results show that the conductivity components driven by these two mechanisms follow distinct trigonometric dependencies on the canting angle. Crucially, we identify a hidden C110 rotational
symmetry that has been previously overlooked in static
magnetic group analyses. By expanding the AHC in terms of
spin orientation vectors, we demonstrate that this
symmetry acts as a bridge connecting distinct
magnetic configurations with different canting angles, thereby strictly protecting the equivalence of orthogonal conductivity components in the collinear system.
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All authors Yuansheng Bu, Ziyin Song, Zhong Fang, Quansheng Wu, Hongming Weng
Strongly Correlated Electrons
Symmetry group factorization and unitary equivalence among Temperley-Lieb integrable models
Huan-Qiang Zhou
It is shown that there is a hidden connection between the two well-studied sequences of the Temperley-Lieb (TL) integrable models – the $q$-state
quantum Potts (QP) models at the self-dual points and the staggered ${\rm SU}(n)$
spin-$s$ chains with $n=2s+1$ ($s \ge 1$), in addition to the uniform ${\rm SU}(2)$
spin-$1/2$ Heisenberg model. For each sequence,
symmetry group factorization arises, in the sense that if $q$ is factorized into $q_1$ and $q_2$, then the $q$-state QP model is unitarily equivalent to a combined QP model with the
symmetry group ${\rm S}_{q_1} \times {\rm S}_{q_2}$ or if $n$ is factorized into $n_1$ and $n_2$, then the staggered ${\rm SU}(n)$
spin-$s$ chain with the
symmetry group ${\rm SU}(n)$ is unitarily equivalent to a combined staggered ${\rm SU}(n_1) \times {\rm SU}(n_2)$
spin chain with the
symmetry group ${\rm SU}(n_1) \times {\rm SU}(n_2)$, valid for both
ferromagnetic (FM) and
antiferromagnetic (AF) cases. Moreover, the FM (AF) staggered ${\rm SU}(n)$
spin-$s$ chain is unitarily equivalent to the AF (FM) $q$-state QP model with $q=n^2$, as long as the size of the AF (FM) staggered ${\rm SU}(n)$
spin-$s$ chain is doubled. A combination of the two distinct types of
unitary equivalences yields a family of models such that they are essentially identical, but appear in different guises. Some physical implications for
unitary equivalence among different TL integrable models are clarified.
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Strongly Correlated Electrons
Green parafermions as emergent flat-band excitations in condensed matter
Huan-Qiang Zhou, Ian P. McCulloch and Murray T. Batchelor
Green parafermions, originally introduced by Green and extended by Greenberg and Messiah through trilinear and relative trilinear commutation relations beyond Bose-
Fermi statistics, are generally regarded as mathematical curiosities without physical realization. We show that these paraparticles can in fact emerge as composite excitations in a broad class of condensed-matter systems undergoing spontaneous
symmetry breaking with type-B Goldstone modes. The key ingredient is the introduction of auxiliary Majorana
fermions defined on emergent unit
cells produced by partial translational-
symmetry breaking. When the auxiliary Majoranas are treated as physical degrees of freedom, the resulting Green parafermion states (up to a projection operator) correspond to flat-band excitations, whose creation and annihilation operators satisfy the trilinear
algebra. When they are regarded as fictitious, the same construction explains the appearance of exponentially many degenerate ground states and reveals a surprising correspondence between Green parafermions and self-similar
geometric objects, such as the golden spiral. Explicit realizations are demonstrated for the
ferromagnetic spin-1 biquadratic model and the
ferromagnetic $\rm {SU}(2)$ flat-band Tasaki model, showing that condensed-matter systems with type-B Goldstone modes provide a natural setting for Green parafermions as emergent, possibly observable quasiparticles.
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Materials Science
Towards Computational Microscope of Chemical Order-Disorder via ML-Accelerated Monte Carlo Simulation
Fanli Zhou, Hao Chen, Pengxiang Xu et al. (+3 more)
Tailoring the performance of next-generation high
entropy materials requires a deep understanding of the competition between
entropy-driven random solid solution and enthalpy-driven chemical ordering. Investigating such order and disorder complexity demands atomistic simulations that achieve high accuracy, efficiency, and generalizability across vast spatial, temporal, and especially chemical scales. While machine learning (ML) interatomic potentials have transformed molecular dynamics, they remain limited in capturing
diffusion-driven chemical
evolution over long timescales. The recently introduced SMC-X method brings exciting opportunities. Realizing its full potential requires a comprehensive study, which is the focus of this work. To assess model performance, we systematically
benchmark invariant and equivariant architectures using a density functional theory
dataset of more than 10,000 configurations spanning seven elements: Fe, Co, Ni, Al, Ti, Ta, and V. To understand the roles of pairwise and higher-order interactions, we decouple their contributions across chemical space using an explainable machine learning approach. We also examine the impact of
lattice relaxation by comparing models trained on
datasets with and without structural relaxation. Our results clarify how to choose ML surrogate models for Monte Carlo simulations, bridge the gap between theory and experiment, and lay a foundation for establishing ML-accelerated Monte Carlo as a computational microscope for chemical complexity.
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All authors Fanli Zhou, Hao Chen, Pengxiang Xu, Kai Yang, Zongrui Pei, Xianglin Liu
Strongly Correlated Electrons
Orbital-specific Itinerancy and Localization in a Kagome Magnet
S.V. Streltsov, H.Y. Huang, A. Ushakov et al. (+10 more)
The kagome
lattice naturally hosts flat bands, Dirac
fermions, and van Hove singularities, yet whether its geometry can stabilize orbital-selective phases - a hallmark of Hund's physics in multi-orbital correlated systems - has remained an open question. Here, we combine resonant inelastic X-ray scattering with density functional theory and dynamical mean-field theory to demonstrate that YMn$_6$Sn$_6$ exhibits a spontaneous orbital differentiation into coexisting itinerant and localized electrons within the same Mn $3d$
manifold. Orbitals directed along Mn-Mn bonds provide coherent quasiparticles and metallic bands, while those pointing toward ligands become strongly correlated and display non-
Fermi-
liquid behavior. Hund's intra-atomic exchange suppresses orbital fluctuations, stabilizing this dichotomy and providing a natural double-exchange-like mechanism for the observed
ferromagnetic bilayer coupling. Our work establishes YMn$_6$Sn$_6$ as a kagome platform where orbital selectivity, flat-band
topology, and Hund's
metallicity converge - revealing that
geometric frustration and correlation-driven orbital differentiation can cooperatively design exotic
quantum phases beyond the canonical paradigms of Mott physics or band
topology alone.
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All authors S.V. Streltsov, H.Y. Huang, A. Ushakov, C.I. Wu, A. Singh, J. Su, J. Okamoto, C.T. Chen, K. Wang, A.I. Poteryaev, S-W. Cheong, A. Fujimori, D. J. Huang
Quantum Gases · Cross-listed from math-ph
The non-uniform electron gas
Mihaly A. Csirik and Andre Laestadius
The non-uniform (or inhomogeneous) electron gas has received much
attention in many-body
quantum mechanics and
quantum chemistry in the early days of density functional theory, mainly as a theoretical device to construct gradient approximations via linear response theory. In this article, motivated by the recent works of Lewin, Lieb and Seiringer, we propose a definition of the
quantum (resp. classical) non-uniform electron gas through the use of the grand-canonical Levy-Lieb functional (resp. the grand-canonical strictly correlated electrons functional), establish these systems as rigorous thermodynamic limits and analyze their basic properties. The non-uniformity of the gas comes from an arbitrary
lattice-periodic background density.
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Materials Science
First Plasma Atomic Layer Etching of Diamond via O$_2$/Kr Chemistry
Duc Duy Tran, Cedric Mannequin, Aboulaye Traore et al. (+2 more)
We report the first
plasma atomic layer etching (ALE) process for diamond using a cyclic
plasma sequence composed of two separated steps: oxygen surface modification and krypton ion removal. The process is implemented in an inductively coupled
plasma reactor using alternating O$_2$
plasma exposure and low-energy Kr ion bombardment. This cyclic process exhibits the characteristic self-limiting behavior of ALE and enables controlled material removal with atomic-scale precision. An etch depth per cycle of \SI{6.85}{\angstrom} was achieved. Surface analysis reveals that the etched diamond surfaces exhibit lower roughness than the pristine material, while XPS confirms the preservation of the diamond bonding structure and indicates essentially damage-free etching. These results demonstrate that
plasma ALE based on O$_2$/Kr chemistry provides a viable route toward damage-controlled nanoscale processing of diamond, opening new opportunities for advanced device fabrication in power electronics, photonics,
quantum sensing and
quantum computing technologies.
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All authors Duc Duy Tran, Cedric Mannequin, Aboulaye Traore, Masahiro Sasaki, Etienne Gheeraert
Materials Science
Framework for Quasiperiodic Interfaces: Proximal Coincidence Point Set and Computation
Suining Xiong, Wenwen Zou, Pingwen Zhang et al. (+1 more)
We present a unified theoretical and computational framework that bridges mathematical quasiperiodicity with classical crystallographic models. Based on a rigorous cut-and-projection construction, the proposed proximal coincidence point set (PCPS) theory extends the classical coincidence site
lattice model and further incorporates physically motivated perturbations encoding interfacial atomic mobility as well as visual indistinguishability. Spectral characteristics of PCPS naturally motivate a conserved Landau-Brazovskii model combined with projection method, yielding unified high accuracy in resolving quasiperiodic order across the entire interfacial plane. Representative quasiperiodic features are revealed in our numerical results, including generalized Fibonacci sequences in BCC [110] tilt GBs, as well as repetitive patterns within the interstices of dislocation networks in low-angle BCC [100] twist GBs and phase boundaries between BCC and face-centered cubic
crystals. In high-angle BCC [100] twist GBs, 12- and 8-fold quasicrystals emerge, while the PCPS theory combined with cyclotomic field projections further explains their restrictions of non-crystallographic
symmetries. This framework not only provides a rigorous theoretical explanation for interface structures but also offers a path toward modeling other types of incommensurate structures.
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All authors Suining Xiong, Wenwen Zou, Pingwen Zhang, Kai Jiang
Strongly Correlated Electrons
Yu-Feng Mao, Shicheng Ma and Yong Xu
Despite long-standing theoretical interest, the
chiral spin liquid, a topologically ordered phase, has yet to be observed experimentally. Here we surprisingly find its emergence in an experimentally realized dipolar $\text{XY}$ model when Rydberg atoms are arranged in a breathing kagome
lattice. Using the infinite density
matrix renormalization group, we numerically calculate the ground state's
chiral order parameter,
spin-
spin correlations, Chern number, and
entanglement spectrum. Our numerical results provide strong evidence for the
chiral spin liquid phase. Furthermore, we identify a
quantum phase transition from a Dirac
spin liquid to a
chiral spin liquid as the
lattice geometry is tuned from the isotropic kagome to the breathing kagome
lattice.
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Materials Science
Unlocking Static Polarization and Strain Density Waves in Perovskites by Softening a Hidden Antiferrodistortive Tilt Gradient Mode
Yajun Zhang, Devesh R. Kripalani, Xu He et al. (+9 more)
Spin density waves (SDWs) represent a fundamental paradigm of spatially modulated order in condensed matter systems, yet their electrical and mechanical analogues polarization and strain density waves (PDWs and StDWs) have remained elusive as
equilibrium phases. Here, we introduce a general,
symmetry-driven strategy to unlock static PDWs and StDWs in perovskites SrTiO3 and SrMnO3. Using first-principles calculations, we uncover a previously overlooked soft antiferrodistortive tilt gradient mode at small-q wavevector in the
phonon dispersion of their presumed Ima2 ground state under moderate tensile strain. Group-theory analysis reveals that a hard polaracoustic
phonon, which intrinsically carries PDWs and StDWs, is improperly destabilized by a trilinear coupling with this modulated tilt mode and an inherently uniform tilt mode. This interaction drives a structural transition from the Ima2 phase to a novel lower-energy Pmn21 phase that hosts long-range-ordered PDWs and StDWs. Strikingly, the engineered StDWs in SrMnO3 activate an electrically tunable SDW via the flexomagnetic effect. These discoveries fundamentally revise the strain-phase diagrams of prototypical perovskites and establish a unified
phonon-engineering framework that links modulated
phonon instabilities to targeted density-wave order, offering new pathways for designing advanced electromechanical and magnetoelectric functionalities.
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All authors Yajun Zhang, Devesh R. Kripalani, Xu He, Konstantin Shapovalov, Jiyuan Yang, Hongjian Zhao, Shi Liu, Huadong Yong, Xingyi Zhang, Jie Wang, Kun Zhou, Philippe Ghosez
Soft Condensed Matter
Isometric Incompatibility in Growing Elastic Sheets
Yafei Zhang, Michael Moshe and Eran Sharon
Geometric incompatibility, the inability of a material's rest state to be realized in Euclidean space, underlies shape formation in natural and synthetic thin sheets. Classical Gauss and Mainardi-Codazzi-Peterson (MCP) incompatibilities explain many patterns in nature, but they do not exhaust the mechanisms that frustrate thin elastic sheets. We identify a new incompatibility that forbids smooth stretching-free configurations, even when the rest state of the elastic sheet locally satisfies the Gauss and MCP compatibility conditions. We demonstrate this principle in a model of surface growth with positive Gaussian
curvature, where a
geometric horizon forms, leading to the onset of frustration. Experiments, simulations, and theory show that the sheet responds by nucleating periodic d-cone-like dimples. We show that this obstruction to stretching-free configurations is topological, and we point to open questions concerning the origin of frustration.
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Materials Science
High Entropy Alloy under Shock Compression: Optical-Pump X-Ray-Probe
Hsin Hui Huang, Meguya Ryu, Shuji Kamegaki et al. (+23 more)
High
entropy alloys (HEAs) are multi-principal-element
alloys designed for tailorable mechanical performance and have been attracting significant engineering interest, yet their fundamental behaviour under extreme dynamic conditions, such as shock loading, remains unexplored. Here, we report
laser-shock experiments on two different types of 1-micrometers-thick HEA microfilms, CuPdAgPtAu and CrFeCoNiCuMo, on 25-micrometers-thick black-Kapton ablator driven by a high intensity
laser pulse (532 nm, 5 ns, 16 J, 0.5-mm diameter focal spot) and probed by an X-ray free electron
laser (XFEL) pulse (12 keV, 7 fs). Time-resolved X-ray diffraction (XRD) shows the formation of a transient phase with a
lattice compression up to 5.1% of the CuPdAgPtAu HEA along the (111) plane; this transient compressed phase existed for 0.3 ns. The impedance matching Hugoniot analysis estimated a shock pressure of 55 +/- 6 GPa in the HEA film, while Au- and Fe-based equations of state (EoS) modelling predict 80 GPa (0.8 MBar) at the free HEA surface. The free HEA surface reached maximum velocities of ~ 5 km/s as recorded from in situ monitoring with the velocity interferometry system for any reflector (VISAR) imaging. These initial HEA results show the suitability of HEA sample preparation and XFEL-based XRD characterisation under extreme shock loading, and are promising for experimental determination of the EoS of this emerging class of materials (beamtime proposal No.: 2024A8503 for a 6-hour preliminary experiment).
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All authors Hsin Hui Huang, Meguya Ryu, Shuji Kamegaki, Dominyka Stonyte, Tadas Malinauskas, Yoshiaki Nishijima, Rosalie Hocking, Nguyen Hoai An Le, Tomas Katkus, Haoran Mu, Soon Hock Ng, Samuel Pinches, Andrew S.M. Ang, Vygantas Mizeikis, Nadia Zatsepin, Kohei Miyanishi, Toshinori Yabuuchi, Hirotaka Nakamura, Alexis Amouretti, Norimasa Ozaki, Tommaso Vinci, Arturas Vailionis, Eugene G. Gamaly, Damien G. Hicks, Junko Morikawa, Saulius Juodkazis
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Robust Quantum Sensing via Prethermal Spin Orbits
Enrico Daniel Richter, Ryan J. Smith, Brayden Glockzin et al. (+3 more)
Practical performance of
quantum sensors is often curtailed by uncontrolled environmental drift (bias-field instability, temperature fluctuations, mechanical vibration), background fields, and imperfect control pulses. This motivates developing physical mechanisms that intrinsically compensate for such perturbations while retaining high sensitivity to target fields. We introduce an interaction-protected magnetometry scheme where periodic driving steers the collective magnetization onto two long-lived, prethermal Floquet "orbit" axes well-separated on the Bloch sphere. Rapid toggling between these axes encodes target fields as a differential signal, whereas background fields appear as common-mode motion that is strongly rejected, achieving >1000-fold suppression while canceling prethermal transients. This enables accurate reconstruction of rapidly varying audio-band
magnetic signals without predictive filtering or spectral tuning. We provide an experimental proof-of-principle using a dense ensemble of coupled
nuclear spins, operated here as a broadband (0-1 kHz) magnetometer. The protocol is remarkably tolerant to imperfections, operating robustly across millions of pulses under pulse-angle (~10{\deg}) and pulse frequency (>1 kHz) errors, large bias-field drifts (>50 $\mathrm{\mu}$T), temperature variations over 150 K, and harsh mechanical vibrations. These results establish Floquet prethermalization as a resource for robust
quantum sensors that combines broadband
magnetic-field sensitivity with intrinsic immunity to diverse environmental and control perturbations, opening a path toward stable
quantum metrology beyond controlled laboratory conditions.
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All authors Enrico Daniel Richter, Ryan J. Smith, Brayden Glockzin, Emanuel Druga, Thomas Schenkel, Ashok Ajoy
Other Condensed Matter
Gate-Drain Leakage Enhanced by Drain-Induced Dielectric Barrier Lowering in Gate-All-Around Field Effect Transistors
Juan P. Mendez, Coleman Cariker, Michael Titze et al. (+2 more)
Gate-All-Around Field-Effect Transistors (GAAFETs), now entering high-volume production as successors to fin field-effect transistor technology, are enabling continued scaling and enhanced performance in advanced
semiconductor nodes. However, the drain-current in GAAFETs strongly deviates from the thermionic dependence at negative gate voltages, exhibiting the existence of leakage that is additionally enhanced at high applied biases. Understanding the origin of this leakage is essential for determining the scaling limits of GAAFETs and for guiding device and material optimizations aimed at suppressing the off-state current. Additionally, recent experimental measurements have revealed the increased influence of radiation-induced defects in the negative gate voltage regime, with their impact remaining largely negligible for positive gate voltages. Through predictive first-principles simulations, we demonstrate that the observed leakage current at negative gate voltages originates from gate-to-drain tunneling, which is significantly enhanced by drain-induced dielectric barrier lowering between the gate and drain.
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All authors Juan P. Mendez, Coleman Cariker, Michael Titze, Alex A. Belianinov, Denis Mamaluy