Other Condensed Matter
$\mathcal{PT}$-symmetry as Effective Time Reversal Symmetry for Anderson Localization in a Collinear Antiferromagnet
Kim-Khuong Huynh, Takuma Ogasawara, Motoi Kimata et al. (+7 more)
We show that $\mathcal{PT}$-
symmetry acts as the effective time-reversal
symmetry governing Anderson localization in the antiferromagnet BaMn$_2$Bi$_2$, whereas the general time-reversal
symmetry is broken by its long-range
magnetic order. The magnetoconductance follows the laws established from breaking time-reversal
symmetry throuhg the orbital coupling of charge carriers to the magnet vector potential, however, the degrees of
symmetry breaking are qualitatively modulated by the magnetocrystalline anisotropy stabilizing $\mathcal{PT}$-related sublattices. The
quantum interferences and hoping amplitudes governing the phenomena are drastically impaired by transverse
magnetic fields, which readily cant $\mathcal{PT}$-related
magnetic sublattices. Accordingly, when the $\mathcal{PT}$-related texture is weakly perturbed by longitudinal fields orienting along the sublattices, the localization is minutely affected. The robustness of the $\mathcal{PT}$-enforced degeneracies is thus governed by exchange and magnetocrystalline interactions, in contrast to the exact $\mathcal{PT}$-
symmetry of the full
Hamiltonian, which is broken by any finite field.
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All authors Kim-Khuong Huynh, Takuma Ogasawara, Motoi Kimata, Sofie Søby Leiszner, Nhu-Quynh Thi Phan, Michael Anthony Quintero, Frej Søren Rattenborg, Denis Arčon, Bo Brummerstedt Iversen, Katsumi Tanigaki
Materials Science
Interplay between spinodal decomposition and wetting in ternary to quinary mixtures
Sandeep Kumar and Supriyo Ghosh
We use two-dimensional phase-field simulations based on the Cahn–Hilliard description to study spinodal decomposition in N-component mixtures with N = 3, 4, 5. In particular, we consider surface-directed spinodal decomposition in which one of the coexisting phases serves as a filler particle, while the remaining components phase separate around its surface. We investigate both nonwetting and wetting conditions by varying the interfacial tensions between the particle and the other components. The competition between wetting kinetics and spinodal decomposition produces rich morphological
evolution, including the formation of
lattice, droplet, and target (or core-shell) morphologies. The target pattern consists of alternating component-rich rings around the particle. In the intermediate-to-late time regime, these structures undergo further morphological transitions driven by
curvature-induced depletion of wetting layers and subsequent coarsening of the surrounding domains, resulting in the breakup of target patterns into isolated domains of the
matrix components. We find that domain coarsening slows down systematically as the number of components increases, while wetting accelerates it in all cases. The resulting morphologies and phase-separation pathways demonstrate how particle–component interactions can be used to control microstructural
evolution in multicomponent mixtures, with potential implications for systems ranging from industrial materials to cellular biology.
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Materials Science
Time-Reversal Selection Rule for Twist Disorder
Peng Kang, Da Wan, Shulin Bai et al. (+7 more)
Random layer rotations are ubiquitous in layered matter, from turbostratic films to rotationally disordered
crystals, and strongly suppress transport across the layers. Generated by a
symmetry operation, this disorder is absent on the rotation axis, so the thickness laws of conduction are set by how fast backscattering vanishes there. We show that a time-reversal selection rule decides this: each twist harmonic of the interlayer bond is either a frame rotation, whose backscattering cancels, or a coupling change, which scatters. A zero-set
theorem turns the rule into universal thickness laws for electrons and
phonons, fixed by band-edge
symmetry; random twist increments rescale the backscattering but keep its order. Where the axis is unprotected, band nodes provide a second route: a transparent energy with heavy-tailed disorder and an $N^{-3}$ law. A first-principles forward-channel model of black phosphorus shows both routes; its random-twist films act as a
symmetry filter that, relative to aligned stacks, retains a hundred times more of the electron than of the hole conductance at 64 layers. The
symmetry of band edges and
phonon branches thus decides what crosses a disordered stack, making stacking disorder a design element.
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All authors Peng Kang, Da Wan, Shulin Bai, Pengfei Zhang, Vincent Michaud-Rioux, Zhen Li, Yu Liu, Lei Zheng, Li-Dong Zhao, Huibin Xu
Statistical Mechanics · Cross-listed from math.PR
Uniform Bessel bounds for magnetization crossings in finite Ising chains
Arjun Pemmasani
In a finite zero-field Ising chain, the all-up configuration and zero magnetization become equally likely at a single coupling. This crossing has recently been described as a thermal transition of the finite chain, an analogue of a first-order transition temperature, and approximated by an analytic estimate and a numerical fit. We find its asymptotics, with explicit constants, for free and for periodic ends. The coupling at the crossing grows like half the logarithm of the length of the chain, minus half the logarithm of that logarithm. So the correlation length at the crossing is a vanishing fraction of the chain. Periodic ends lower the coupling at the crossing by an amount that decays like the inverse logarithm of the length. The earlier approximations lack the doubly logarithmic term, which explains why a fit on chains of moderate length finds a slope below one half. The proofs treat the magnetization as the position of a persistent random walk and compare its central probability with a modified Bessel function, with a relative error bound that is explicit for every length. For free ends this traps the crossing in an explicit interval at every length. The proof is analytic for long chains and uses exact integer arithmetic for short ones. We also locate, for each smaller magnetization, the coupling at which it becomes as likely as full magnetization.
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Statistical Mechanics
Active lattice percolation: an apparently new universality class of percolation transitions
Vernon M. Hughes and David A. Huse
We investigate a class of dynamic percolation models on a
lattice, in which connections are added and removed by a set of local
stochastic rules. In particular, the removal of any connection that can result in one connected cluster becoming two (or more) separate clusters is strictly forbidden. These models include and are inspired by a model for local
quantum error correction for a toric code studied by Chirame, et al., PRX
Quantum 6, 030363 (2025), who identified a phase transition with first-order characteristics, such as bistability and a discontinuous order parameter. We show numerically that this transition is a hybrid percolation transition (HPT), having characteristics of a continuous percolation transition such as diverging critical clusters while at the same transition having discontinuities like a first-order transition. We then modify this model to be fully isotropic, showing that the HPT remains. In both of these models, the steady state on one side of the HPT is an absorbing state; by turning on additional isotropic local
stochastic moves, we remove the absorbing state and strongly suppress or remove the first-order transition, leaving an apparently continuous percolation transition. Curiously, the numerically-observed percolation critical exponents do not change significantly between the models with hybrid transitions and the model with an apparently continuous transition. These exponents are significantly different from known percolation transitions, indicating that this may be a new universality class.
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Materials Science
Quantitative near-atomic-resolution oxidation-state mapping in complex oxide heterostructures by electron energy-loss spectroscopy
Ioannis Iatrakis, Zitao Zhang, Ricardo Egoavil et al. (+3 more)
We present a theoretical framework for quantitative oxidation state mapping of transition-metal and rare-earth elements from near-atomic-resolution electron energy-loss spectroscopy (EELS) in complex oxide
heterostructures. The total inelastic differential cross section of transition-metal L$_{2,3}$ and rare-earth M$_{4,5}$ edges is calculated by combining the relaxed Dirac-Hartree-Fock ionization cross section with ligand-field multiplet theory for the discrete transitions. We apply the approach to two correlated-oxide
heterostructures, La$_{0.67}$Sr$_{0.33}$MnO$_3$/LaCr$_{0.2}$Mn$_{0.2}$Fe$_{0.2}$Co$_{0.2}$Ni$_{0.2}$O$_3$/SrTiO$_3$ and NdNiO$_3$/La$_{0.67}$Sr$_{0.33}$MnO$_3$/NdGaO$_3$, which include a wide range of transition-metal and rare-earth elements with overlapping features. The method resolves the oxidation states of Cr, Mn, Fe and Co and identifies the Ni contribution within the LaCr$_{0.2}$Mn$_{0.2}$Fe$_{0.2}$Co$_{0.2}$Ni$_{0.2}$O$_3$ layer at near-atomic resolution. We find predominantly Co$^{2+}$ together with mixed Mn$^{2+}$/Mn$^{3+}$/Mn$^{4+}$ character, indicating site-specific valence redistribution within the layer. We also separate overlapping spectral features, such as La-M$_{4,5}$ and Ni-L$_{2,3}$ edges in the NdNiO$_3$/La$_{0.67}$Sr$_{0.33}$MnO$_3$/NdGaO$_3$
heterostructure, thereby recovering the intrinsic Ni-L$_{2,3}$ excitation spectrum. We find that the effective Ni valence in NdNiO$_3$ deviates from the simple ionic picture. More broadly, this work establishes a generic method for quantitative valence mapping from near-atomic-resolution EELS, applicable to a wide range of experimental conditions for the study of local electronic structure of complex oxides.
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All authors Ioannis Iatrakis, Zitao Zhang, Ricardo Egoavil, Emma van der Minne, Christoph Baeumer, Frank de Groot
Materials Science
Site-Specific Orbital Symmetry Breaking in Epitaxial Graphene on Silicon Carbide
Vinod K. Paidi, Yves Joly, Alex Taekyung Lee et al. (+5 more)
The epitaxial
graphene grown on SiC interface has been the subject of tremendous research efforts to control its electronic transport properties in the quest for
graphene electronic applications. The electronic structure of the epitaxial
graphene buffer layer on SiC(0001) is investigated at the atomic scale using monochromated electron energy loss spectroscopy (EELS) in an aberration-corrected scanning transmission electron microscope (STEM). The C $K$-edge reveals spectral fine structures distinctly different from free-standing
graphene layer, providing direct experimental evidence of a modified bonding environment. Ab initio calculations providing a site-resolved probe of orbital character to elucidate the origin of these spectral features: covalent bonding between one-quarter of the buffer-layer carbon atoms and the substrate silicon atoms induces partial $\mathrm{sp}^3$ hybridization, quenching the out-of-plane $\pi$ states and disrupting $\pi$-conjugation across the interfacial layer. Substrate-imposed
symmetry breaking further lifts the in-plane orbital degeneracy. This orbital-engineering framework, rooted in $\pi$-state quenching and site-specific
symmetry breaking, establishes a quantitative basis for tailoring
graphene-substrate interfaces toward next-generation low-energy transistor applications.
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All authors Vinod K. Paidi, Yves Joly, Alex Taekyung Lee, Guillaume Radtke, Vlado K. Lazarov, Demie Kepaptsoglou, Quentin M. Ramasse, Matthieu Bugnet
Mesoscale and Nanoscale Physics
Anisotropic Friedel oscillations and isoperimetric transport in two-dimensional free lattice Fermi seas
Guillermo R. Zemba
Two physical consequences of the recent topological classification of 2d Fermi seas for free particles based on flat orbifolds $\mathbb{R}^2/\Gamma$ of discrete
symmetry $\Gamma$, are explored. The first is a study of the spatial density behavior inside the mesoscopic window enclosed by the Fermi and (infinite) thermal lengths. It is shown that the single-particle density
matrix exhibits a sharp directional anisotropy, encoding a real space diffraction pattern, i.e., a Fraunhofer-like diagram of the Fermi sea, that reveals the point-group
symmetries of the background
lattice $\Gamma$ in the form of anisotropic Friedel oscillations. As examples, the special cases of the $p4m$ and $p6m$ crystallographic flat orbifolds are treated in some detail. The second physical consequence is the establishment of an explicit
geometric correspondence between momentum-space packing and electrical transport. A mean-field expression for the longitudinal electrical conductivity $\sigma_{xx}$ as a function of the isoperimetric parameter $\cal{I}$ of the occupied orbifold domain by utilizing
geometric measure theory is presented, satisfiying the scaling law $ \sigma_{xx} \propto 1/\sqrt{\cal{I}}$. The topological transport formula naturally incorporates the vanishing conductivity ($\sigma_{xx} \to 0$) of the previously described “
geometric insulators,” promoting the isoperimetric parameter as an efficient descriptor for topological and
geometric phases in conductors.
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Materials Science
Wavelength-Dependent Photoluminescence Mapping of Depth-Dependent Degradation Under Thermal Stress in Phenethylammonium Tetrafluoroborate Treated Perovskite Solar Cells
Julisa Juarez, Akash Dasgupta, Alan Zhan et al. (+2 more)
Studying real-time degradation in perovskite
semiconductors remains an important challenge. Conventional methods often cannot separate interfacial and bulk processes or rely on destructive analysis. Here, we demonstrate multiwavelength excitation photoluminescence (PL) as a nondestructive approach to distinguish interface- and bulk-dominated recombination losses. Using phenethylammonium tetrafluoroborate (PEABF4) treatment as a model, we use PL to show that PEABF4 passivates the electron transport layer (ETL)/perovskite interface, reducing interfacial recombination losses from fullerene deposition. However, upon thermal aging, PEABF4-treated stacks degrade more rapidly, with recombination losses broadening from the ETL/perovskite interface into the absorber.
Diffusion-recombination simulations support interpreting excitation-wavelength-dependent PL decay signatures consistent with changes in surface recombination velocity and bulk lifetime, providing a framework for depth-sensitive comparisons during aging. Collectively, these results further establish multiwavelength excitation PL as a platform for studying recombination losses during aging of perovskite films.
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All authors Julisa Juarez, Akash Dasgupta, Alan Zhan, Lamtiur P. Samosir, David S. Ginger*
Materials Science
The Hidden Cost of Two-Dimensional TEM Reconstruction of Magnetic Nanoparticle Morphology
Iago López-Vázquez, Amira Páez, Yilian Fernández-Afonso et al. (+6 more)
Conventional transmission electron microscopy (TEM) records two-dimensional (2D) projections of three-dimensional (3D) objects, complicating the inference of nanoparticle morphology. This limitation is investigated for quasi-spherical iron oxide nanoparticles (IONPs) imaged after deposition on a TEM grid and after cellular internalization and immobilization in resin. A statistical inverse-reconstruction method is developed in which synthetic 3D particle populations are randomly oriented, projected onto a TEM-like plane, and compared with the experimental equivalent-diameter and axial-ratio distributions. Models of increasing geometrical complexity are considered, from monodisperse prolate spheroids to size- and shape-polydisperse prolate populations and triaxial ellipsoids. Size polydispersity is required to reproduce the projected equivalent-diameter distribution, whereas relaxing axial
symmetry through a triaxial description enables simultaneous reproduction of the size and axial-ratio distributions. The inferred population represents a statistically compatible 3D morphology rather than a unique particle-by-particle reconstruction. Its physical relevance is assessed through a macrospin model incorporating the corresponding shape-anisotropy contributions. Application to
magnetic fluid hyperthermia reveals a pronounced sensitivity of the predicted heating response to particle geometry and polydispersity. The approach provides a general framework for connecting conventional TEM measurements with morphology-dependent properties of nanoparticle ensembles.
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All authors Iago López-Vázquez, Amira Páez, Yilian Fernández-Afonso, Roy W. Chantrell, Thomas S. van Zanten, Sergiu Ruta, Lucía Gutiérrez, Òscar Iglesias, David Serantes
Strongly Correlated Electrons
Peeling off Abelian Anyons and Proliferation Transitions
Meng Cheng and Nathan Seiberg
We study the invertible one-form global
symmetry of a (2+1)-dimensional topological
quantum field theory (TQFT). A universal description of this
symmetry “peels off” all the Abelian anyons from the rest of the TQFT. This allows us to study this
symmetry and some of its consequences, independently of the details of the rest of the system. We then describe these Abelian anyons using $\mathrm{U}(1)$ gauge fields with Chern-Simons terms and couple them to a scalar field, thus constructing a particular non-topological theory. This new theory, our transition field theory, exhibits a phase transition from the original TQFT to another phase. The latter is either gapless or another TQFT. This discussion generalizes and extends our earlier work (arXiv:2603.00245). In particular, we give a more detailed description of the global
symmetries and their fates in the various phases.
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Mesoscale and Nanoscale Physics
Electron-phonon control of obstructed and quantum spin Hall topology in an altermagnet
Kuntal Bhattacharyya, Bilal Tanatar and Saurabh Basu
We theoretically demonstrate control over the interplay between obstructed atomic insulating and first-order topological phases via electron-
phonon coupling (EPC) in a $d$-wave altermagnet (AM) that hosts nonrelativistic
spin-split bands with zero net magnetization. By
embedding a $d_{x^{2}-y^{2}}$-wave AM in a
quantum spin Hall (QSH)
insulator, we show that an altermagnetic order beyond a critical strength reconstructs the parent QSH state of a Bernevig-Hughes-Zhang (BHZ)-type topological
insulator (TI) into an obstructed atomic
insulator (OAI), characterized by nontrivial bulk polarization with quantized fractional corner charges, accompanied by characteristic in-gap boundary states, while the
spin Chern number vanishes. Upon incorporating sufficiently strong EPC, the polaronic dressing reorganizes the Wannier centers and the associated effective edge
topology, thereby weakening the altermagnetism-induced OAI phase and restoring the helical QSH edge modes. Further, EPC eventually drives the system into a trivial
insulator. By uncovering a controllable switching mechanism between topologically distinct insulating phases in AMs, our study establishes a direct route toward
phonon-tuned spintronic functionalities in unconventional
magnetic platforms.
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Strongly Correlated Electrons
Does a pole in the self-energy imply a violation of the Luttinger theorem?
Artem Abanov and Andrey Chubukov
Luttinger
theorem relates Fermi surface volume to electron density per
spin $n$. It holds in an arbitrary Fermi
liquid but is widely believed to break when a fermionic self-energy has a pole. We show that this is not necessarily the case. As an example, we consider a fermionic system consisting of two gapped bands, originating from a self-energy $\Sigma (\omega, \mathbf{k})$ with a pole, and a narrow residual quasiparticle band crossing $\omega =0$, with a small residue $Z \ll 1$ (a residual Fermi
liquid). We consider Model I, in which $Z$ also renormalizes quasiparticle bandwidth $W$ to $ZW$ and Model II, in which $W$ remains unrenormalized. The Green's function for such a system $G(\omega, \mathbf{k})$ contains two zeros and three poles — one from the quasiparticle band and two from the gapped bands. Yet, we show that in Model I, the Luttinger-Ward analysis is fully applicable for any $Z >0$, and the results are exactly the same as if the gapped bands did not exist. For Model II, the Luttinger-Ward analysis recovers once $Z$ exceeds some critical value, which depends on fermionic density.
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Strongly Correlated Electrons
Determining the j-Specific Unoccupied 5f Electronic Structure in Actinides
J. G. Tobin
An empirical comparison of high resolution M4,5 X-ray Absorption Spectroscopy (XAS), based upon High Energy Resolution Fluorescence Detection (HERFD), with Bremsstrahlung Isochromat Spectroscopy (BIS), the high energy variant of Inverse Photoelectron Spectroscopy (IPES), of various actinide materials is presented here. It will be shown that XAS-HERFD is essentially the j-specific version of BIS, providing a direct measure of the separate 5f5/2 and 5f7/2 Unoccupied Density of States (UDOS).
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Statistical Mechanics
MUTACO: Simulator-Efficient Response Matching in Stochastic Nonlinear Systems via Compatibility-Aware Sequential Design
Ege Karadeniz, İlter Onat Korkmaz, Umut Can Turhan et al. (+2 more)
Many physical inverse problems are mediated by expensive
stochastic simulators for which response gradients, adjoint sensitivities, or a differentiable simulator interface are unavailable. We introduce Multiple Target-based Confident Acquisition (MUTACO), an uncertainty-aware sequential-design method for response matching that requires only noisy forward evaluations and learns the multicomponent response together with its predictive uncertainty. We develop and evaluate MUTACO for a disordered network of
stochastic phase oscillators. The inverse task is to infer statistical properties of the local potential and interactions from macroscopic rotation and synchronization curves under multiple driving conditions. Rather than requiring unique recovery of these statistical properties, MUTACO searches for parameter configurations whose predicted rotation and synchronization responses are compatible with the target response while accounting for predictive uncertainty. This response-centered formulation is appropriate when experimentally accessible observables characterize ensemble statistics rather than a particular microscopic realization. Under strictly limited simulation budgets, MUTACO achieves the lowest held-out response error among the tested adaptive-search, space-filling, and simulation-based inference methods, while also yielding lower parameter-recovery error than the compared methods. These results demonstrate that response-targeted sequential design is a simulator-efficient approach to inverse modeling from finite noisy forward evaluations and suggest broader applicability to
stochastic physical systems with correlated multicomponent responses and weakly constrained parameter directions.
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All authors Ege Karadeniz, İlter Onat Korkmaz, Umut Can Turhan, Cem Tekin, Ayd{\i}n Cem Keser
Mesoscale and Nanoscale Physics
Spatiotemporal imaging of microwave magnetic fields via magnonic coherent splitting
C. K. Wei, Z. J. Chen, J. T. Song et al. (+7 more)
Spatiotemporal microwave
magnetic-field imaging reveals current flow in high-frequency
circuits and nonequilibrium
spin dynamics, yet probes rarely combine calibrated spectral readout, optics-free operation and transient mapping at room temperature. Here ferrimagnetic order in yttrium iron garnet supports coherent coupling from a pump-induced
magnon mode, converting target-field amplitude into a spectral splitting with all-microwave readout. Sampling the calibrated splitting over position and delay reconstructs spatiotemporal imaging of
magnetic fields. Continuous-wave measurement reaches a sensitivity of 58 pT/$\sqrt{\mathrm{Hz}}$ and recovers phases across various powers. Combined with time-resolved frequency-comb spectroscopy, the method reconstructs transient fields with a 130-ns response time. Coplanar-waveguide imaging validates the
magnetic selectivity of the mode-splitting readout, where measured maps agree with simulated
magnetic-field distribution. In a microwave amplifier, our reconstruction resolves nonuniform switching dynamics and detects downstream field suppression from an open-contact fault. Magnonic coherent splitting provides a scalable route for optics-free imaging of spatiotemporal field
evolution in functional devices.
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All authors C. K. Wei, Z. J. Chen, J. T. Song, S. H. Ma, W. H. Liu, J. H. Wu, Z. W. Huang, Jinwei Rao, Wei Lu, Bimu Yao
Materials Science
Development and Application of a Magnetoelectric Coupling Measurement System for Strain-Mediated Effects
Samanway Mohanta, Poonacha C.T, Hemant Singh et al. (+6 more)
This paper reports about development of a dynamic lock-in based magnetoelectric (ME) coupling measurement system and its application to investigate strain-mediated coupling in 0.65Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_3$-0.35PbTiO$_3$/NiFe$_2$O$_4$ (PMN-PT/NFO) and CoFe$_2$O$_4$/BaTiO$_3$ (CFO/BTO) composites. The PMN-PT/NFO composite exhibits a significantly enhanced ME coefficient ($\alpha_{\mathrm{ME}} \approx 1.85$~mV\,mm$^{-1}$\,Oe$^{-1}$) compared to CFO/BTO ($\approx 0.147$~mV\,mm$^{-1}$\,Oe$^{-1}$). The antisymmetric field dependence and $180^\circ$ phase reversal confirm the strain-driven origin of coupling in both the samples. The superior response of PMN-PT/NFO arises from the combined effect of high piezoelectric strength in PMN-PT and low
magnetic anisotropy of NFO, whereas the high
magnetic anisotropy of CFO and weaker piezoelectricity of BTO limit the ME output. These results highlight the decisive role of
magnetic softness and piezoelectric strength in optimizing strain-mediated ME coupling.
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All authors Samanway Mohanta, Poonacha C.T, Hemant Singh, Gunjan Verma, A. Ahlawat, S.C. Das, G. Sinha, V. G. Sathe, D. K. Shukla
Mesoscale and Nanoscale Physics
Micromagnet engineering for enhanced addressability of donor-cluster arrays in silicon
Hao Wang, Baolong Zhao, Shihang Zhang et al. (+11 more)
Phosphorus donors in silicon are one of the promising platforms for fault-tolerant
quantum computing, owing to their long coherence times and compatibility with complementary metal-oxide-
semiconductor (CMOS) technology. However, a key bottleneck for scaling this platform lies in the independent addressability of individual
spin qubits. Here, we present a scalable
quantum processor architecture that integrates scanning tunneling microscope (STM)-defined phosphorus donor-cluster arrays with on-chip micromagnets. By generating
magnetic field gradients, the micromagnets enable a broader addressable frequency range compared to the addressing scheme based solely on variations in hyperfine (HF) interactions, which arise from the randomness of intra-cluster configurations. Through micromagnetic simulations to optimize micromagnet geometry, we demonstrate that these structures are compatible with customized array designs, facilitating the integration of over 120 atomic
spin qubits and enabling frequency multiplexing with a single microwave
antenna, which greatly reduces the overhead of fan-out addressing lines. This design is further validated via
magnetic measurements, which generally align with our micromagnetic simulations. These results establish a critical foundation for the development of scalable silicon
quantum computing with atomic
qubits.
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All authors Hao Wang, Baolong Zhao, Shihang Zhang, Ziliang Jin, Huan Shu, Peihao Huang, Guanyong Wang, Mingchao Duan, Tianluo Pan, Tao Xin, Guangchong Hu, Zhen Tian, Dapeng Yu, Yu He
Materials Science
Emergent magnetic nonanalyticity in Dirac altermagnets
Xizhi Fu, Zhenqiao Huang, Fei Yang et al. (+3 more)
Symmetry has long provided the organizing principle for understanding how materials respond to external perturbations. Here we show that what is permitted by
symmetry need not be what actually emerges from the underlying system, and this distinction becomes particularly consequential for
symmetry-related gapless Dirac
fermions such as in altermagnets. A perturbation that shifts the Dirac points drives a Lifshitz reconstruction and generates an intrinsically nonanalytic effective potential, giving rise to undiscovered singular responses. In Dirac altermagnets, this nonanalyticity acquires a
magnetic manifestation through $C$-paired
spin-polarized Dirac cones: breaking the pairing
symmetry $C$ lifts their degeneracy and converts the associated Lifshitz reconstruction into an itinerant magnetization. As a consequence, piezomagnetism, the induction of a net magnetization by a mechanical strain, becomes nonlinear and nonanalytic, with $M\propto\mathrm{sgn}(\varepsilon)\varepsilon^2$, whereas the linear response is absent despite being allowed by
symmetry. Accordingly, the leading response cannot be inferred from the conventional
symmetry-based paradigm of material response built upon the cornerstones of Neumann's principle and analytic Landau expansion. First-principles calculations identify the monolayer Fe$_2$S as a candidate material realization for such singular
magnetic responses. These results suggest
quantum singularities as a new degree of freedom for engineering material responses.
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All authors Xizhi Fu, Zhenqiao Huang, Fei Yang, Mengli Hu, Xingkai Cheng, Junwei Liu
Quantum Gases
Quasi-solitons of the 1D Bose gas at arbitrary-strength contact repulsion
Anahita Sarvi, Cesare Vianello and Jean-Sébastien Caux
Harnessing integrability at arbitrary interaction strength, we build long-lived and spatially localized
soliton-like excitations in the 1D Bose gas with contact repulsion (Lieb-Liniger model). We show how these density profiles, built from selective superpositions of multi-hole eigenstates, display long lifetimes tunable through parameters like dispersion width and number of holes. We further illustrate a scaling protocol that in principle enables unbounded increase in lifetimes in the thermodynamic limit. Our results showcase classical-like excitations originating from
unitary quantum dynamics, away from the semi-classical regime, and in regions where interactions cannot be treated perturbatively.
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Other Condensed Matter · Cross-listed from astro-ph.HE
A Vortex Avalanche Model for Pulsar Glitches
M. Ali Alpar and Erbil Gügercinoğlu
Pulsar glitches are thought to involve sudden unpinning and fast transport of large numbers of pinned
vortices, possibly triggered by breaking of the
neutron star crust solid. Such a
vortex avalanche can take place on a fast timescale only if there are pathways for fast
vortex motion. Formation of local
vortex “traps” (regions containing larger than average density of pinned
vortices) will provide
vortex-free regions surrounding the traps, which can connect to form pathways for fast
vortex motion. We propose a simple two-dimensional model for the
neutron star crust superfluid, with the
vortex pinning landscape tiled into traps and surrounding
vortex-free regions which can connect to azimuthal pathways for fast
vortex motion. The trap and tile sizes are estimated from the physics of the crust solid and
vortex pinning, namely the critical strain angle of the crust solid and the critical velocity for
vortex unpinning. Unpinned
vortices move with the superfluid flow in the azimuthal direction while also scattering radially outward, by a small angle, due to mutual friction. The model qualitatively explains the glitch parameters and their
evolution in young
pulsars and provides an explanation for the bi-modality in the distribution of glitch magnitudes. Laboratory experiments and simulations on
vortex systems with spatially inhomogeneous
vortex pinning landscapes are likely to be more realistic models for
pulsar glitches. Breaking the spatial scale-invariance and monitoring the results may also lead to better understanding of collective behaviour in pinned
vortex systems in general.
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Mesoscale and Nanoscale Physics · Cross-listed from hep-th
Wald entropy and Wen-Zee type gauge-curvature coupling in 2+1-dimensional gravity
Aryan Bhatia, Giandomenico Palumbo and Suraj S. Hegde
The Wen-Zee term is a mixed gauge-
curvature coupling in the topological Chern-Simons description of a
quantum Hall fluid, encoding the electric charge bound to spatial
curvature. We investigate a Lorentz-covariant generalisation of this coupling, expanding its scope to black-hole spacetimes and determine its contribution to horizon
entropy. Such a coupling arises naturally in three-dimensional Chern-Simons
gravity based on the Maxwell
algebra. We show that its Wald
entropy contribution is a horizon boost charge, given by a loop integral of the additional gauge field projected along the tangent to the bifurcation circle. This contribution can be nonzero even when the mixed term vanishes on shell. We show that the integral admits an Abelian holonomy interpretation when the projection direction is covariantly constant. We evaluate the charge on a flat cosmological solution and, using smooth horizon fields and a specified thermal ensemble, on an AdS-Lorentz black hole. These results connect the
geometric response familiar from
quantum Hall physics to gravitational horizon thermodynamics.
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Statistical Mechanics
From Equilibrium Criticality to Universal Collective Phases through Nonreciprocal Coupling of Ordered Systems
Fabrizio Rippa, Jacopo A. Garofalo and Eugenio Lippiello
Nonreciprocal interactions have emerged as a fundamental driver of collective behavior far from
equilibrium. Here, we show that nonreciprocal couplings between
spin systems whose isolated dynamics favors ordered states, beyond the previously identified oscillatory (swap) phase, give rise to a richer nonequilibrium phenomenology, including a multistable regime where ordered and disordered states coexist, a scenario strictly forbidden in
equilibrium. Crucially, we show that this nonequilibrium phenomenology is inherited directly from the critical properties of the underlying isolated model. In particular, tricriticality in the isolated system gives rise to multistability, hysteresis, and hard excitations in the oscillatory dynamics, while non-normal interactions further enrich the phase diagram by generating multistability. Moving beyond mean-field theory, we derive a universal field equation governing the onset of these nonreciprocal oscillations in finite dimensions. Our results establish a unified theoretical framework connecting critical phenomena, dynamical systems, and non-reciprocal collective dynamics, with applications ranging from opinion dynamics to active matter
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Superconductivity
Trapping magnetic flux quanta in superconducting 3D caps
Igor Bogush, Vladimir M. Fomin and Oleksandr Dobrovolskiy
Magnetic flux quanta in type-II
superconductors are topological excitations of the order parameter whose sensitivity to the local environment makes them probes of current density,
magnetic fields, and pinning landscapes. Yet, in planar thin films, individual
vortices are difficult to manipulate, often requiring intricate nanopatterning or demanding scanning-probe instrumentation. Here, we show that shaping a superconducting thin film into a three-dimensional curved geometry enables controllable
vortex trapping under a spatially uniform applied
magnetic field. Employing a conformal formulation of the time-dependent Ginzburg-Landau equation, we simulate
vortex dynamics in a cap-shaped superconducting membrane and compare it with a planar reference.
Curvature converts the uniform applied
magnetic field into a nonuniform local normal component, creating a reconfigurable asymmetric rim-pinning potential tunable by
magnetic-field orientation. Rotating the
magnetic field therefore controls the number and positions of
vortices trapped along the rim. Moreover, the asymmetric pinning produces a superconducting diode effect through current-direction-dependent
vortex capture. Three-dimensional
curvature thus provides a route to engineer local
vortex pinning and realize fluxonic devices with
magnetic-field-programmable
vortex trapping and transport.
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Soft Condensed Matter
Compression-controlled dynamic buckling in thin soft sheets
Harsh Jain, Shankar Ghosh and Kirti Chandra Sahu
We investigate experimentally the dynamic phase transition from compressed to buckled phases for thin sheets of rubber. We find that the rubber strips enter a highly compressed, metastable state when compression speed is high. During the compressed phase, higher modes grow, followed by mode coarsening. Mode growth is accompanied by an expansion of length while the system is still being compressed. We measure the forces and length of the sheet to confirm this, and we develop a mechanism for how modes grow and coarsen during dynamical buckling. The influence of crucial control parameters in the experiments, such as the material cross section and compression speed, on the buckling dynamics, are explained theoretically.
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Quantum Gases · Cross-listed from math.AP
Complete classification of solutions for spin-1 Bose-Einstein condensates in R
Xiao Luo, Cunxin Wei, Juncheng Wei et al. (+1 more)
Spin-1 Bose-Einstein condensates provide a fundamental platform for exploring
quantum magnetism and coherent
spin dynamics. Their three Zeeman components are coupled by
spin-exchange interactions under conserved particle number and magnetization, giving rise to rich
magnetic phases and nonlinear
spin structures; a rigorous classification of stationary states therefore clarifies the possible
spin configurations and their physical origins. In this paper, as a continuation of our previous work \cite{LLWZ23,LLWZ24,LLWZ26}, we study the classification of solution for the
spin-1 Bose-Einstein condensates in $\mathbb{R}$, by applying the non-standard Hirota's bilinear method, the determinant formula and the general left-uniqueness strategy, we present some novel explicit solution and give the complete classification of the solutions. In comparison with the classical Hirota's method, the non-standard Hirota's method needs to introduce auxiliary functions to construct Hirota's bilinear form, which essentially adds additional constraint on the wave functions, so that it possible to deal with more complex equations. As far as we know, this is the first systematic study the complete classification of solutions to the
spin-1 Bose-Einstein condensates. Our classification results yields experimentally testable predictions for
spin populations, relative phases, and
magnetic textures
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All authors Xiao Luo, Cunxin Wei, Juncheng Wei, Maoding Zhen
Materials Science
Kilovolt-class Vertical (011) e̱ta}-Ga2O3 Schottky Diodes for High Voltage and High Temperature Applications
Emerson J. Hollar, Aaron M. Adams, Nolan S. Hendricks et al. (+2 more)
We report kilovolt-class vertical (011) e̱ta}-Ga2O3 Schottky diodes utilizing high-permittivity dielectric TiO2/Al2O3 field-plate for high voltage and high temperature applications. A systematic study was performed with Pt/(011) e̱ta}-Ga2O3 Schottky barrier diodes (SBDs) with varied diameters from 100 {\mu}m to 300 {\mu}m, for both with and without field-plate, that revealed excellent consistency of reverse blocking performance regardless of diode area. The field-plate SBDs achieved superior breakdown voltages (3.90 - 4.16 kV) compared to the diodes without field-plate (3.06 - 3.16 kV) owing to effective edge termination. Furthermore, we explored high-temperature performance of the field-plate (011) e̱ta}-Ga2O3 diodes that revealed excellent forward conduction properties and high rectification ratio (~10^9) throughout the temperature range (25 - 150 C). At reverse bias, the field-plate diodes also exhibited kV-range breakdown voltage with no evident increase in leakage current up to the explored elevated temperature of 150 C. The low area-dependence of breakdown voltage, excellent forward transport properties, and minimal reverse leakage at both high-voltage and elevated temperature demonstrate the exciting potential of (011) e̱ta}-Ga2O3 SBDs in high-temperature power switches. Thus, our work demonstrates the strategy of advancing the performance of vertical e̱ta}-Ga2O3 SBDs by utilizing the advantageous (011) e̱ta}-Ga2O3 epilayers with low background doping, reduced killer dislocation effects, and effective field management for high-voltage and high-temperature applications.
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All authors Emerson J. Hollar, Aaron M. Adams, Nolan S. Hendricks, Andrew J. Green, Esmat Farzana
Soft Condensed Matter
Activated coarsening of motility-induced phase separation in random environments
Parameshwaran A and Bhaskar Sen Gupta
Self-propelled particles that only repel one another can still separate into a dense and a dilute phase, a process known as motility-induced phase separation (MIPS). In a clean system the domains coarsen like any conserved mixture: domains grow as $\ell(t)\sim t^{1/3}$. Living and synthetic swimmers, however, move through rough, porous, or patterned surroundings. Using large-scale simulations of active Brownian particles, we ask how frozen heterogeneity changes MIPS coarsening. We introduce disorder in two ways, as a quenched random force field acting on particle positions and as a quenched random torque field acting on their orientations. Both destroy Lifshitz-Slyozov growth. A transient power law with a disorder-dependent exponent gives way to activated dynamics in which the effective dynamic exponent grows without bound and domains grow at most logarithmically. The crossover obeys the scaling form known from the random-field Ising model, and the domain morphology depends on disorder strength, so superuniversality fails. The two kinds of disorder act through different mechanisms. Random forces trap particles in the sinks of a random drift field once the drift beats self-propulsion. Random torques act as a sign-random, quenched chirality that erodes persistence and lowers the local Péclet number toward its critical value. Our results show that quenched disorder is a relevant perturbation for the kinetics of active phase separation and connect MIPS coarsening to the physics of pinned interfaces in disordered magnets.
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Strongly Correlated Electrons
State-selective entanglement and point-gap topology in the unidirectional Bose-Hubbard chain
Chuan-Fu Lin, Yu-Chin Tzeng and Po-Yao Chang
We study the effect of repulsive interactions on skin modes and
entanglement in the unidirectional Bose–Hubbard model. Although the ground state of this integrable model undergoes a superfluid–Mott transition with suppressed skin accumulation, the corresponding change in
entanglement depends on the selected many-body state. We compare the ground state with the steady state, defined as the largest-imaginary-energy eigenstate in the zero-momentum sector. For sixteen sites at unit filling, we find that the ground-state density approaches uniform filling and its
entanglement decreases toward the Mott limit, whereas the steady states exhibit a nonmonotonic
entanglement crossover. At intermediate interaction ($U/t=10$), the second Rényi
entropy of the steady state develops four spatial maxima. We show that these maxima are accounted for by competing subsystem-number sectors within a dominant configuration
manifold of four doublons and four holons, but not by the subsystem particle-number variance alone. The dominant global onsite-pair
manifold retains the same
entropy peak structure. At strong interaction, projection onto the one-doublon–one-holon
manifold closely reproduces the full
entropy profile and its two edge peaks. Furthermore, we demonstrate that the many-body winding about the origin remains nonzero at strong interaction; an exact two-site example shows how it becomes ill-defined in the singular projected $U/t\to\infty$ limit. Our results distinguish ground-state skin suppression from state-selective
entanglement and point-gap
topology.
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