We show that intercalating a WSe$_2$ monolayer into bilayer graphene creates a synthetic bilayer graphene at the Fermi level, in which WSe$_2$-mediated wavefunction overlap hybridizes the two graphene layers, giving rise to states delocalized across both layers. Because the interlayer coupling is comparable in energy to the proximity-induced spin-orbit interaction, the resulting spintronic behavior goes beyond what is typically accessible in conventional single-interface proximity systems. A simple four-electrode device, with source and drain electrodes on both the top and bottom graphene layers, gives access to distinct regimes depending on which electrodes are activated. The most prominent feature is a nonlocal Rashba-Edelstein effect, activated via cross-layer source and drain electrodes, in which a charge current injected into one graphene layer generates a spin accumulation in the spatially separated opposite layer. This effect is robust to the twist angle modulation between graphene and WSe$_2$ and to the applied electric field, suggesting that a moderate degree of structural asymmetry along the vertical direction does not destroy it. In addition, activating the source and drain electrodes on either the top or bottom graphene layer reveals local Rashba-Edelstein signals of opposite sign in the two layers, thereby realizing a layer-selective chirality switch. This is a consequence of the hidden Rashba effect, which is present even when a net Rashba splitting is forbidden. Our results suggest new physical regimes and device architectures that could be useful for spintronic applications.
Author(s): Yi Ren, Shan Dong, Zheng Vitto Han, Wen-Kai Lou, and Kai Chang
The recently synthesized quasihexagonal-phase fullerene network (${\mathrm{qHPC}}_{60}$) offers opportunities for 2D electronics. Through first-principles calculations, we reveal that ${\mathrm{qHPC}}_{60}/\mathrm{graphene}$ van der Waals heterostructures exhibit unique electronic properties, includ…
[Phys. Rev. B 114, 125415] Published Mon Aug 17, 2026
Charge transfer between two conductors is conventionally viewed as a single-particle process governed by electrostatics and band alignment. Using tunneling spectroscopy, we show that charge transfer in closely spaced graphene double layer quantum Hall ferromagnets instead proceeds through a sequence of interaction driven phase transitions governed by the competition between capacitive charging and Coulomb exchange interactions. A comparison of experimental data and theoretical calculations identifies spectroscopic signatures of the interaction driven charge transfer transitions, and reveals that this charge transfer reconstructs the quasiparticle spectrum. While intralayer exchange favors abrupt transfer of entire spin-valley subbands between the layers, interlayer exchange stabilizes coherent intermediate phases that enable gradual charge transfer. Our results establish interlayer tunneling as a powerful probe of interacting electronic systems whose quasiparticle spectrum is itself bias dependent.
Topologically protected Majorana zero modes (MZMs) have attracted intense interest due to their potential application in fault-tolerant quantum computation (TQC). Graphene nanoribbons, with tunable edge terminations and compatibility with planar device architectures, offer a promising alternative to semiconductor nanowires. Here we present a comprehensive theoretical study of finite graphene strips with armchair, zigzag, and nearly square geometries, proximitized by an s-wave superconductor and subject to Rashba spin-orbit coupling, Zeeman fields, and disorder. Using exact diagonalization of the Bogoliubov-de Gennes tight-binding Hamiltonian, we analyze Majorana polarization, low-energy spectra, and real-space wavefunctions to identify the non-trivial topological phases supporting MZMs and distinguish them from from partially separated Andreev bound states (psABS) or the quasi-Majoranas. We systematically chart the robustness of these modes across geometries and disorder regimes, finding that armchair strips with short zigzag edges provide the most stable platform. Our results unify polarization diagnostics with spatial wavefunction analysis and disorder effects, yielding concrete design guidelines for graphene-based topological superconductors.
Author(s): R. David Mayrhofer and Andrey V. Chubukov
In experiments on Bernal bilayer graphene under perpendicular electric field, quantum oscillations have shown the presence of electronic nematic states in some ranges of hole density. Here, the authors perform a Hartree-Fock study to numerically determine where nematic states develop in the system as hole density and displacement field are varied. Nematic phases are found close to the boundary between fully and partially isospin polarized phases. An analytic criterion for the appearance of nematicity is also derived. It is in good agreement with the numerical results.
[Phys. Rev. B 114, 115114] Published Mon Aug 17, 2026
In 1991, it was proposed that fourfold-degenerate Landau levels formed by a single species of electrons could host a non-Abelian fractional quantum Hall (FQH) state with Fibonacci anyons at filling fraction $\nu = \frac{2}{3}$. In this work, we investigate how such degenerate Landau levels can be realized in rhombohedral-stacked tetralayer graphene. We identify the following key conditions which may stabilize the Fibonacci state: (1) A magnetic field of around 20 Tesla is required if surface and interior carbons have the same energy level. If substrate hybridization raises the surface carbon energy level by $\Delta_2 = 30$\,meV relative to interior carbon, the required field will have a larger range: 15 -- 20 Tesla. For $\Delta_2 = 45$\,meV, the range reaches a maximum: 7 -- 20 Tesla. (2) The displacement field must be tuned to achieve Landau level degeneracy. $\nu = \frac{3}{5}$ Fibonacci FQH states may also be realized in pentalayer rhombohedral graphene with a magnetic field of 12 Tesla, and $\nu = \frac12$ states with Ising anyons may occur in trilayer graphene for magnetic fields of 12 -- 20 Tesla at $\Delta_2 = 0$ or 5 -- 20 Tesla at $\Delta_2 = 45$\,meV. We also study a simple interaction model to explore spin/valley polarization effects, and we see that the Fibonacci statemay occur at $\nu = 2/3 + $ integer filling fractions, where the integer is 0 and 4 for sufficiently weak interaction, or can shift to 2 and 5 under a stronger interaction. The case $\Delta_2 = 45$\,meV also produces states at negative filling fraction, e.g. $-\frac23$, $-4\frac23$. Here $\nu$ is defined with respect to the Hall conductance, $\sigma_{xy} = \nu \frac{e^2}{h}$.
We present CMesh, a polymer‐free carbon nanotube (CNT) mesh scaffold for robust TEM specimen preparation of graphene and porous graphene. Fabricated by simple vacuum filtration, CMesh acts as a porous mechanical reinforcement layer during transfer, avoiding direct contact between graphene and a continuous sacrificial polymer support such as PMMA. Under the optimized condition using 0.5 mL of 0.05 mg/mL CNT stock dispersion, CMesh provides dense suspended pockets as TEM/STEM imaging windows while enabling transfer onto standard low‐cost TEM grids. Fresh CMesh‐supported pristine graphene shows a STEM‐segmented cleanliness of 53 ± 6% without post‐transfer cleaning. With CMesh reinforcement, pristine graphene and 2 s O 2 plasma‐treated porous graphene show high coverages of 99.4 ± 0.3% and 99.4 ± 0.2%, respectively, on standard 400‐mesh Cu grids, reducing grid cost by ∼60–200‐fold compared with specialized supports. The resulting specimens support atomic‐resolution TEM/STEM imaging, remain structurally stable during in situ heating up to 900°C, and retain large‐area integrity after approximately one year of storage.
The standard Mott formula is widely used to describe thermoelectric transport, but it becomes less accurate when the temperature is not much smaller than the Fermi energy. In this work, we develop an all-orders extension of the Mott approach using a series of Riemann zeta functions. We show that when the transport function is a polynomial, the series ends after a finite number of terms, giving exact results within the model. We apply this method to graphene photothermoelectric devices using a quadratic conductivity model. The results provide closed-form expressions for the Seebeck coefficient, Lorenz ratio, and electronic figure of merit. The analysis shows that the Seebeck coefficient reaches a maximum instead of increasing indefinitely, while the Wiedemann-Franz law can be significantly violated at higher temperatures. We also find that disorder reduces the thermoelectric performance and that the electronic figure of merit has an upper limit in the clean graphene model. Finally, we discuss the effect of radiative heat transport on the figure of merit. These results provide a simple analytical way to study graphene thermoelectric transport beyond the usual low-temperature Mott approximation.
We report the realization of a gate-defined quantum point contact (QPC) in bilayer graphene proximitized by a single aluminum superconducting electrode. Superconducting correlations induced in the ballistic channel enhance the conductance plateaus beyond their normal-state values. In addition, we observe a pronounced above-gap conductance anomaly which serves as a spectroscopic signature of the loss of superconductivity and the associated collapse of the Andreev excess current. By reconstructing the nonlinear current-voltage characteristics, we find that the magnitude of the excess current increases as successive QPC modes are populated. Additionally, we find that the switching current associated with the loss of superconductivity follows the underlying mode structure of the QPC, exhibiting discrete levels consistent with a heat dissipation-driven transition. These results demonstrate that the one-dimensional transport modes of the QPC govern both the equilibrium proximity effect and the non-equilibrium dynamics of the hybrid system.
Pnictogen chalcohalide (MChX; M=Bi,Sb; Ch=S,Se; X=I,Br) solid solutions combine earth-abundant constituents, tunable band gaps ($1.2$-$2.1$ eV), and strong optical absorption, making them attractive for solar energy conversion. Yet their vast compositional space has so far prevented a systematic assessment of how band-edge positions vary with stoichiometry and surface termination. Here, we combine first-principles density functional theory with machine learning to predict the valence and conduction band-edge positions of $\mathrm{Bi}_x\mathrm{Sb}_{1-x}\mathrm{S}_y\mathrm{Se}_{1-y}\mathrm{I}_z\mathrm{Br}_{1-z}$ solid solutions across their full compositional range on the two most stable surfaces, (010) and (011). We find that the valence-band maximum and conduction-band minimum can be tuned by more than $1$ eV through composition alone, and shift by up to $0.6$ eV between the two surface terminations for a same composition despite their nearly degenerate formation energies, establishing facet selection as a design parameter on par with chemical substitution. Guided by these results, we identify specific compositions capable of driving hydrogen, ammonia, methane, hydrogen peroxide, and oxygen (photo)electrochemical half-reactions, and show that several electron- and hole-transport contact materials commonly used in photovoltaic devices align with MChX solid solutions only as hole-selective contacts.
Fano resonances, arising from the interference between discrete and continuum states, are observed across a wide range of quantum and classical systems. Here, we report the experimental observation of Fano resonances in a graphene SiNx hybrid nanomechanical system modeled as coupled oscillators. The broad, low quality factor graphene mode plays the role of the continuum, while the dense comb of sharp, high quality factor SiNx modes provides the discrete states. The inter-mode detuning is tunable via a DC gate voltage, enabling dynamic control of the Fano resonance: we demonstrate gate controlled switching of both the sign and the magnitude of the Fano asymmetry parameter $q$, in quantitative agreement with a coupled oscillator theory that predicts $q=-\cot\phi$, with $\phi$ the phase of the continuum response. At strong drive, the graphene mode enters the Duffing regime and its jump-down frequency locks to successive SiNx modes, producing a staircase of drive insensitive frequency plateaus; a weak seeding tone deterministically switches the resonator between adjacent locked states. The dense SiNx mode thus acts, in the linear regime, as the discrete states of a tunable Fano interferometer and, in the nonlinear regime, as a frequency ruler that stabilizes and quantizes the graphene oscillation. This platform offers a controllable mechanical realization of Fano interference and opens new avenues for high resolution hybrid resonant sensors and stable nanomechanical frequency references.
Rare-earth chalcogenide perovskites have attracted significant attention for optoelectronic applications due to their nontoxic composition, robust phase stability, and excellent optoelectronic properties. However, their excitonic and polaronic properties remain largely unexplored due to the high computational cost of accurate theoretical treatments. In this work, we present a comprehensive first-principles investigation of excitonic dynamics and polaronic effects in a series of III-III rare-earth chalcogenide perovskites ABX$_{3}$ (A = Y, La; B = Sc, Y; X = S, Se), along with their structural stability and optoelectronic properties, using state-of-the-art density functional theory in conjunction with many-body perturbation theory within the G$_{0}$W$_{0}$ and Bethe-Salpeter equation (BSE) frameworks. All investigated compounds satisfy the dynamical and mechanical stability criteria. They exhibit quasiparticle band gaps in the range of 2.75$-$4.47 eV, and the BSE calculations reveal strong optical absorption spanning the visible to ultraviolet regions. The computed excitonic properties indicate intermediate-to-large exciton binding energies (0.148$-$0.517 eV), moderately localized excitons, and strong electron-hole wavefunction overlap, indicative of favorable radiative recombination characteristics and enhanced light-matter interaction. Furthermore, analysis based on the Fr\"ohlich model demonstrates intermediate-to-strong carrier-phonon coupling, with electron-phonon interactions generally stronger than hole-phonon interactions. Overall, rare-earth chalcogenide perovskites ABX$_{3}$ exhibit a compelling combination of structural stability, tunable optoelectronic properties, pronounced excitonic effects, and favorable polaronic transport, positioning them as promising lead-free materials for next-generation optoelectronic devices, including light-emitting devices and photodetectors.
Point defects in atomically thin materials have a strong impact on physical properties and those that induce in-gap states are advantageous for quantum information science and engineering (QISE). However, dopant engineering consisting of well-controlled synthesis and robust identification of in-gap states is challenging. In this work, we addressed this challenge by first using finely tuned chemical vapor deposition to incorporate vanadium dopants into a monolayer WS2 (V-WS2). Next, we utilized a suite of scanned probe microscopy techniques to identify and characterize individual dopants. The latter included conductive atomic force microscopy (cAFM), low temperature scanning tunneling microscopy and spectroscopy (STM/STS), and scanning transmission electron microscopy and unambiguously revealed that vanadium dopants form deep in-gap states 0.35 eV above the valence band maximum in V-WS2. Our experimental results are well supported by first principles calculations and taken together demonstrate that V-WS2 is a promising platform for QISE applications.
Nature Reviews Physics, Published online: 17 August 2026; doi:10.1038/s42254-026-00970-5
van der Waals Josephson junctions offer opportunities to explore novel device functionalities in superconducting circuits. This Review discusses progress in different device architectures and provides a roadmap outlining near-term and long-term opportunities for the field.The magnetic structure of a magnetic topological semimetal EuMnSb$_2$ is investigated in fields up to 30 T using polarized and unpolarized neutron diffraction, pulsed-field x-ray magnetic circular dichroism and pulsed-field magnetometry. We determine the zero-field magnetic structures of the Eu and Mn sublattices, and find that magnetic transitions induced by applied fields below 2 T correspond to changes in the magnetic order of the Eu spins alone without detectable perturbation to the order of the Mn spins. An additional magnetic transition is observed at fields close to the saturation field for the Eu spins. We present a mean-field model which describes key features of the magnetic behavior and allows us to estimate the dominant Eu--Eu and Eu--Mn exchange interactions responsible for the coupling between magnetism and electronic topology.
Author(s): Yi Peng, Chao Yang, Haiping Hu, and Yucheng Wang
Robust states emerging at the boundaries of a system are an important hallmark of topological matter. Here, using the Su-Schrieffer-Heeger model and the Kitaev chain as examples, we study the impact of a type of experimentally realizable bond dissipation on topological systems by calculating the ste…
[Phys. Rev. B 114, 084203] Published Mon Aug 17, 2026
Metal halide perovskite nanoplatelets combine quantum confinement with structural anisotropy, yet how thickness and processing govern their internal crystal lattice versus collective organization remains unresolved. In this study, we separate internal structure, superlattice organization, and film texture using 2-5 monolayer CsPbBr3 nanoplatelets and larger nanocrystals across spin-coating and drop-casting routes. Grazing incidence X-ray diffraction analysis of the specimens indicates that orthorhombic-compatible signatures recur throughout the thickness and deposition series, with a preserved lattice-morphology relationship in which 020/040 and 101/202 lattice planes are associated with the platelet thickness and lateral dimensions, respectively. Upon deposition on the substrate, we notice a thickness-dependent crossover: 2-monolayer nanoplatelets remain predominantly face-on across deposition routes, whereas thicker nanoplatelets show marked processing sensitivity and orientational disorder. Processing therefore can be used as a tool to direct the NPL packing, establishing thickness as a key determinant of processing sensitivity.
Helium bubbles and grain boundaries in tungsten plasma-facing components alter hydrogen-isotope transport and thermal conduction by orders of magnitude, yet evaluating these transport properties for a given microstructure requires hours of molecular dynamics (MD) per configuration. We present a graph neural network surrogate that maps a tungsten atomic configuration containing helium bubbles and grain boundaries directly to the full $3\times3$ symmetric tensors of the hydrogen diffusion coefficient $D_H(T)$ and the thermal conductivity $\kappa(T)$ at arbitrary temperature. Anisotropy is captured by a rotation-equivariant tensor pooling layer; temperature enters through predicted temperature-independent parameters (an Arrhenius pair $(D_0,E_a)$, a phonon conductivity tensor, and a defect residual resistivity) expanded analytically via the Arrhenius and Wiedemann-Franz-Matthiessen relations. Training labels for 635 microstructures are generated with an embedded-atom-method potential (Green-Kubo conductivity and multi-temperature tracer diffusion); the electronic channel is calibrated against published irradiation-degradation measurements, and the pipeline is anchored to a first-principles machine-learning potential (VASP+FLARE) through paired MD calibration runs and an active-learning loop. The learned activation energies (median 0.21 eV, rising in bubble and grain-boundary structures) reproduce literature hydrogen migration barriers and trapping physics, and the equivariant pooling keeps predictions consistent across arbitrarily oriented sub-blocks. Coupled finite-element thermal-hydrogen analyses driven by the surrogate show that conductivity degradation changes predicted hydrogen permeation by a factor of 2.5 through the temperature field. The model returns both tensors in milliseconds, enabling microstructure-resolved transport input for component-scale analyses of fusion divertors.
We demonstrate that spatially engineered magnetic anisotropy can stabilize skyrmion and meron spin textures in magnetic nanodisks even in the absence of Dzyaloshinskii-Moriya interaction (DMI). Using a constrained analytical model and micromagnetic simulations, we show that competing perpendicular and in-plane anisotropies can generate non-collinear topological textures in non-chiral magnetic systems. We further show that DMI and dipolar interactions lift the helicity degeneracy and select preferred chiral configurations; micromagnetic simulations were used to identify physically stable states. These results establish anisotropy-patterned nanodisks as a platform for studying DMI-free topological spin textures and their controllable magnetic response. We also show that arrays of anisotropy-engineered skyrmions can control spin-wave transmission by manipulating their vorticity arrangement, pointing to reconfigurable magnonic elements based on non-chiral topological textures.
In the search for promising material candidates for hydrogen storage, we investigate from first principles derivatives of metal organic framework 5 (MOF-5), including isoelectronic substitution of the metal centers (Zn $\rightarrow$ Mg, Cd) and linker functionalization with NH$_2$, OH, and NO$_2$ groups. Metal-node substitution consistently stabilises and ligand functionalization systematically enhances H$_2$ binding at the metal-oxo cluster sites. The combination of Cd centers and NO$_2$ groups proves to be most efficient, yielding an adsorption energy of -15.58 kJ mol$^{\text{-1}}$, which substantially outperforms the storage ability of pristine MOF-5. Detailed electronic structure analysis clarifies how the local framework environment coordinates the guest molecule, providing a robust design framework to guide the experimental development of advanced adsorbent materials.
The origin of the proposed bond disproportionated insulating state of the non-centrosymmetric ($Pnn2$) phase of Ag$_{2}$BiO$_{3}$ is explored using first principles electronic structure calculations. The novel insulating state is elucidated by first considering the initially proposed centosymmetric metallic ($Pnna$) phase of Ag$_{2}$BiO$_{3}$. Our calculations reveal that the valence skipping Bi$^{4+}$ ions in this phase are better described as Bi$^{3+}\underline{L}$ with completely filled Bi-(6$s$) states and a ligand hole. However, phonon calculations indicate that the metallic ($Pnna$) state is dynamically unstable. Structural stability is achieved through breathing distortions of the oxygen octahedra, resulting in two inequivalent Bi sites and a reduction of symmetry to the $Pnn2$ phase. Electronic structure calculations further reveal that the $Pnn2$ phase is a bond disproportionated insulator where the nominal charge state of Bi is described by : 2[Bi$^{3+}\underline{L}$ (Bi$^{4+}$)] $\rightarrow$ Bi$^{3+}\underline{L}^{2-\delta}$ (Bi1$^{5+}$) + Bi$^{3+}\underline{L}^{\delta}$ (Bi2$^{3+}$), highlighting the crucial role of ligand holes in driving the insulating state. Next we have investigated the electronic structure of Ag$_{2}$BiO$_{3}$ in the insulating ($Pnn2$) phase including spin-orbit coupling. Our density functional theory (DFT ) calculations complemented by ${\bf k.p}$ model Hamiltonian analysis reveal persistent spin-textures around the $X$ and $Y$ high symmetry points of the orthorhombic Brillouin zone imposed by non-symmorphic symmetry, positioning Ag$_{2}$BiO$_{3}$ as a promising candidate for spintronic applications.
A comprehensive study of second harmonic generation on thermally oxidized MoS 2 flakes with the thickness ranging from monolayer up to seven layers is presented. Observing the fundamental nonlinear behavior for nontreated and oxidized MoS 2 reveals that oxidation causes significant changes in the second harmonic response for all investigated structures. Excitation-power-dependent measurements to analyze the nonlinear behavior with respect to the oxidation time show progressive oxidation within the maximum oxidation time of 6 h under the considered oxidation conditions. Here, polarization-dependent measurements reveal the structural changes due to oxidation. Additionally, it is found that the oxidation depth is restricted to the topmost S layer and the oxidation behavior exhibits a layer dependency. These findings are supported by theoretical band structure calculations. The results demonstrate that the thermal oxidation progress of two-dimensional MoS 2 can be monitored with nonresonant and noninvasive SH microscopy by following the distinct fingerprints of structural modification in the nonlinear response.
Using the DFT+dynamical mean-field theory method we study the effects of electron-electron correlations and epitaxial strain of the crystal structure on the normal-state electronic structure, quasiparticle band renormalizations, Fermi surface, and magnetic correlations of the bilayer Ruddlesden-Popper nickelate La$_3$Ni$_2$O$_7$ (LNO). Our results exhibit a remarkable orbital-selective renormalization and strong incoherence of the Ni $3d$ bands, pointing to the proximity of the Ni $x^2-y^2$ and $3z^2-r^2$ states to orbital-selective localization. The electronic properties of LNO show a high sensitivity to the in-plane strain. We note that both a tensile and a moderate compressive strain (up to about $-2$\%) yield a significant enhancement of magnetic correlations compared to the unstrained LNO. Under a large compressive strain of about $-4$\%, we observe a Lifshitz transition characterized by the disappearance of the $\gamma$ Fermi surface sheet, which is associated with a nearly fully occupied, shallow flat-band of the bonding Ni $3z^2-r^2$ orbital character. As a result, we observe a sharp decrease of magnetic correlations, implying suppression of superconductivity. Overall, our results support the picture of spin- and change-density-wave stripe instability driven by the Fermi surface nesting in LNO. Our results suggest that both pressure and strain can effectively tune (suppress or enhance) spin-change-density-wave ordering, giving rise to enhanced spin fluctuations.
It has been controversial whether infinite projected entangled pair state (PEPS) can faithfully describe chiral gapped phases in two dimensions or not. Finite-bond-dimension PEPS can capture many local and topological properties of chiral phases, but generically develop spurious long-range power-law like correlations. We introduce an auxiliary-assisted framework that bypass this obstruction by embedding the physical chiral system together with an auxiliary time-reversed partner, yielding a non-chiral enlarged representation whose physical chiral sector is recovered with controlled decoupling. For both a free-fermion Chern insulator and an interacting chiral spin liquid, the resulting PEPS show clean gapped correlation functions, and a finite transfer-matrix correlation length, in contrast with the artificial long-range tail of direct chiral PEPS representations. There exist small and negligibly coupling between the physical and auxiliary systems due to the finite entanglement effect, which only affect short-ranged local quantities. Despite the nonchiral enlarged representation, the chiral topological information remains encoded in the entanglement. Using layer-resolved momentum projection, we recover the expected universal chiral entanglement boundary spectrum. Our study provides a practical route to access gapped chiral phases with finite bond-dimension PEPS by changing the representation problem rather than directly studying the chiral pure state.
Author(s): Jose Antonio Moreno, Pablo García Talavera, Edwin Herrera, Sara López Valle, Zhuoqi Li, Lin-Lin Wang, Sergey Bud’ko, Alexander I. Buzdin, Isabel Guillamón, Paul C. Canfield, and Hermann Suderow
Vortex formation from surface superconductivity is observed in the topological semimetal -PtBi, which confirms the robustness of the surface superconductivity at a higher T than the bulk.
[Phys. Rev. Lett. 137, 086001] Published Mon Aug 17, 2026
Hydrogen (H) and deuterium (D) interactions with transition metals play a central role in heterogeneous catalysis and hydrogen-related technologies. While H-Pt surface interactions have been extensively studied, direct investigations of hydrogen incorporation and transport in Pt remain limited due to its low solubility. Here, we study H(D) incorporation and desorption dynamics in metastable $PtH(D)_x$ thin films prepared by low-energy ion irradiation, enabling hydrogen loading far above equilibrium concentrations. Nuclear reaction analysis (NRA) reveals a nonuniform hydrogen depth profile with two accumulation regions: the subsurface and the film-substrate interface. Thermal desorption spectroscopy (TDS) exhibits two desorption peaks near 190 and 230 K, consistent with hydrogen release from these sites. Resistance relaxation measurements, analyzed within a two-parallel-channel conduction model, indicate different relaxation kinetics for subsurface and near-interface hydrogen. Arrhenius analysis reveals two thermally activated processes for $PtH_x$ with an average hydrogen concentration of $x = 0.15$, with activation energies of $130 \pm 18$ meV (subsurface) and $164 \pm 26$ meV (near interface). Above 140 K, D exhibits slower relaxation rates with activation energies of $117 \pm 8$ and $121 \pm 7$ meV for $PtD_x$ prepared under the same implantation dose. Within experimental uncertainty, the activation barriers remain comparable, while the prefactors are reduced significantly for D, indicating isotope-dependent attempt frequencies and zero-point energy effects. TDS simulations based on the Polanyi-Wigner formalism reproduce the experimental desorption spectra by resolving subsurface and near-interface contributions, in agreement with the NRA profile. These findings provide insight into hydrogen kinetics in $PtH_x$ for Pt-based catalysis, sensing, and hydrogen-metal interactions.
Author(s): Jiali Chen, Chaoxi Cui, Zhi-Ming Yu, Wei Jiang, and Yugui Yao
The anomalous Hall conductivity in magnetic Weyl semimetals scales linearly with the momentum separation between Weyl nodes, establishing a geometric paradigm for three-dimensional Hall responses. Here, we discover an analogous phenomenon in the spin Hall effect: a quantized spin Hall conductivity (…
[Phys. Rev. Lett. 137, 086301] Published Mon Aug 17, 2026
In recent years, epsilon-near-zero (ENZ) materials have attracted a great deal of attention in nonlinear optics, as they combine field enhancement with strong, ultrafast nonlinearities. In particular, transparent conducting oxides, such as ITO, have emerged as a promising class of materials and have been extensively exploited to achieve temporal optical responses varying on the femtosecond scale using an optical pump. Most of the solutions discussed so far in the literature rely on effective $\chi^{(3)}$ modulations, wherein the dominant material response is controlled by the envelope of the optical pump. Here, it is shown that low-symmetry conductors can provide an interesting alternative to transparent conducting oxides and a more natural implementation of time-crystalline behavior in optical systems with optical-cycle modulation. I demonstrate that ENZ confinement, combined with the strong anomalous-velocity nonlinearity of low-symmetry conductors, enables a subwavelength nanoparticle to develop a time-crystalline response under optical pumping. For sufficiently strong pumping, this response can overcome dissipative losses and lead to parametric amplification. Furthermore, the pump can strongly tailor the scattering and extinction of a weak probe and, in extreme cases, render the extinction negative. In this regime, the driven nanoparticle effectively amplifies the probe beam.
Most computationally predicted materials are never synthesized because conventional synthesis optimization is slow, expertise-dependent, and iterative. Here we present a closed-loop framework that automates this expert workflow by placing human tacit knowledge in the loop through a large language model (LLM) that distills synthesis knowledge from the literature, high-throughput hyperspectral imaging for rapid film evaluation, and multi-objective Bayesian optimization guided by experimental feedback. In a paired optimization campaign, LLM-assisted initialization produced more Pareto-optimal samples and higher hypervolume than a Latin hypercube sampling baseline at matched trial counts, and this advantage persisted throughout iterative optimization. We demonstrate the framework by synthesizing the previously unreported perovskite-inspired compound Rb3BiI6 as thin films and validating the optimized films by optical bandgap analysis and X-ray diffraction. The framework transforms synthesis prediction from single-shot recommendation to iterative learning, providing a generalizable strategy to accelerate automated and fully autonomous experimental materials discovery.
Electrostatics govern charge transfer and reactivity in materials. However, most foundation potentials (FPs) either neglect explicit electrostatic interactions or come at prohibitive computational cost. Here, we introduce charge-equilibrated TensorNet (QET), an equivariant, charge-aware architecture that achieves linear scaling with system size via an analytically solvable charge-equilibration scheme. We demonstrate that a trained QET FP matches state-of-the-art FPs on materials property benchmarks but delivers qualitatively different predictions in systems dominated by electrostatic interactions. The QET FP reproduces the correct structure and density of the NaCl-CaCl2 ionic liquid and the crystallization of Ge1Sb2Te4 phase change memory, which charge-agnostic FPs miss. We further show that a fine-tuned QET captures reactive processes at the Li/Li6PS5Cl solid-electrolyte interface and supports simulations under applied electrochemical potentials. These results remove a fundamental constraint in large-scale atomistic simulations of electrostatics and establish a general, data-driven framework for charge-aware FPs with transformative applications in energy storage, catalysis, and beyond.
arXiv:2608.12622v2 Announce Type: replace-cross Abstract: We study how boundaries affect Maxwell-Chern-Simons theory, a three-dimensional gauge theory that combines ordinary electromagnetic propagation with a topological Chern-Simons term. On a strip, the two boundaries can support edge excitations while the single massive bulk mode mediates a Casimir interaction between them. We use Symanzik's local boundary-field-theory framework, deriving the boundary conditions from the most general quadratic local boundary action considered here rather than imposing them by hand. Requiring these conditions to act consistently on the unique physical bulk mode selects a continuous family of admissible boundaries, characterized by an impedance and an edge velocity. The associated conserved currents form two boundary current algebras with opposite levels, and for a symmetric strip the edge modes propagate in opposite directions. The bulk and residual edge sectors factorize, leaving a single physical scattering channel for the Casimir problem. We derive its reflection amplitude, identify a stable pole-free domain, and show that the force is attractive there. In the Maxwell limit the usual long-range one-channel Casimir interaction is recovered, whereas the topological mass produces exponential screening at large separation. Outside the pole-free domain, localized surface modes can appear and must be included separately. The analysis provides a unified description of edge dynamics, boundary conditions and vacuum forces in a topologically massive gauge theory.
Rare-earth iron garnets, such as yttrium iron garnet (YIG) and thulium iron garnet (TmIG), are the benchmark magnetic insulators for spintronic and magnonic devices, but achieving usable perpendicular magnetic anisotropy (PMA) in these materials typically relies on substrate strain- engineering, requiring careful lattice-matching and specific growth conditions that constrain ma- terial accessibility. Here we establish sputter grown barium hexaferrite (BaFe12O19, BaM) as a magnetic-insulator alternative with strong intrinsic perpendicular anisotropy, requiring no strain engineering. X-ray diffraction, transmission electron microscopy and Raman spectroscopy confirm stoichiometric films with atomically smooth surfaces, while first-principles calculations corroborate a robust ferrimagnetic ground state. The films exhibit square out-of-plane hysteresis with a coercive field of nearly 0.1 T. Unlike rare-earth garnets, the perpendicular anisotropy in BaM is intrinsic to its magnetoplumbite crystal structure, arising independent of highly ordered strain. Interfaced with Pt and with exfoliated BiSbTeSe2 (BSTS), BaM induces proximity induced anomalous Hall trans- port, confirming efficient interfacial exchange coupling, while the BSTS/BaM heterostructure shows an additional Hall contribution suggestive of non-collinear interfacial spin textures. These results position BaM thin films as a scalable magnetic-insulator platform for spintronic and topological heterostructure devices beyond the constraints of garnet chemistry.
Collective excitations can survive profound changes in the microscopic degrees of freedom that generate them. We track a layer-odd collective response from an exact weak-coupling hybridisation anchor into the paired regime of an attractive Hubbard bilayer and find that its Hamiltonian sensitivities evolve in a manner consistent with a crossover from single-particle interlayer hybridisation towards collective pair superexchange. At weak coupling, an exact identity for identical tunnel-coupled layers fixes a relative-phase Gaussian kernel zero at 2th , independent of the intralayer hopping. Sign-free determinant quantum Monte Carlo reveals an interaction-driven softening of the many-body spectral scale without analytic continuation, while Gaussian response theory supplies the continuous pole interpretation and shows a shift from layer-density to relative-pair-phase character. In the paired regime, the characteristic response scale acquires a growing fractional sensitivity to the intralayer hopping and an interaction dependence partway towards the 1/U law. These results show how a collective excitation can be tracked across a fermion-to-composite-boson crossover while constraining changes in its microscopic drive.
We report a comprehensive temperature-dependent investigation of spin-orbit torque (SOT) generation in heterostructures comprising a perpendicularly magnetized metallic multilayer grown on top of a topological insulator (TI) epilayer. Temperature-dependent second-harmonic Hall measurements reveal distinct trends in the magnitude of the spin-orbit torque across the studied heterostructures. Samples incorporating Bi2Se3 exhibit torques reaching approximately 12 mT/(10^12 A m^-2) at 15 K, around 5 times larger than those in a multilayer without the topological layer. The structure with a thin 2-nm Ta buffer for the multilayer shows the strongest enhancement and a pronounced increase at low temperatures, highlighting efficient spin-current generation from the topological surface states. In contrast, the sample with a 10 nm-thick Ta spacer exhibits reduced torque efficiency, consistent with partial attenuation of spin transmission through the buffer. Systems lacking Bi2Se3 but containing two heavy metals (Ta and Pt) yield significantly smaller torques, around 2.5 mT/(10^12 A m^-2), despite the presence of conventional spin Hall sources. These observations underscore the dominant role of TI-derived spin-momentum-locked currents in driving large damping-like torques and their sensitivity to interfacial structure and buffer-layer thickness.
Data-driven materials discovery interpolates more reliably than it extrapolates and seldom reaches new structure types. We present MatEvolve, an agentic-AI framework designing crystals, proposing each candidate with a stated rationale and testing it. The agent reasons in an interpretable \emph{language of motifs}, writing each crystal as a \emph{motif profile} that describes the recurring geometric patterns---the \emph{motifs}---composing it. The motif profile serves not merely as a description of a material but as the medium for material design: the agent edits the profile and constructs a crystal from the modified one, and the most promising candidates are validated by first-principles calculation. Applied to the design of rare-earth-lean permanent magnets, MatEvolve---built on the state-of-the-art language model Claude Fable~5 without fine-tuning---reaches new structural prototypes more than three times as often as generative models under an equal validation budget, at a comparable on-target-magnet rate. Beyond design, analysing the discovered crystals' human-readable profiles reveals structure--property relationships.
Author(s): Jia-Rui Xu, Zhan Xiong, Kai Deng, Hai-Xiao Wang, Shiyang Liu, Yixian Qian, and Jian-Hua Jiang
Antichiral surface states, which exhibit unidirectional propagation along parallel surfaces, hold significant promise for classical wave manipulation. However, their physical realization typically relies on complex implementations of a two-dimensional modified Haldane model, limiting practical appli…
[Phys. Rev. B 114, 105122] Published Mon Aug 17, 2026
In this work, we adopt a finite strain computational homogenization approach to characterize the response of semi-flexible biopolymer networks modeled as idealized 8- and 14-chain periodic networks. We use the geometrically exact special Cosserat rod theory to model the microscale fibers forming these 8- and 14-chain networks. This allows us to capture arbitrarily large microscale deformations. Both macroscopic strain- and stress-driven homogenization are performed to study the macroscopic uniaxial tension, compression and simple shear responses. Several phenomena unique to biopolymer networks are recovered such as strain-stiffening and volume shrinkage under uniaxial tension, softening under compression and reverse Poynting effect under simple shear. We find that nonlinearity and non-affine deformation at microscale, especially bending and buckling of microscale fibers, plays an important role in these phenomena. We obtain the postbuckled solutions of the homogenization problem using a nonlinear, imperfection-free path following approach and also check for their stability. We further compare our homogenization results with experimental data for uniaxial tension and compression of biofilament networks and find good agreement. When the fibers are replaced by helical rods in the 8-chain unit cell, we are also able to capture the enlarged stretching behaviour as shown in recently fabricated compliant metastructures.
Quantification of electrostatic potentials at the nanoscale is crucial for understanding the principles governing properties of materials across multiple length scales. Currently, one of the most successful approaches relies on the charging response of a molecular quantum dot, suspended on a tip of a scanning probe microscope and measured using dynamic force spectroscopy. We investigate the possibility of an optical detection, aiming to improve the speed and reduce the complexity of this measurement scheme. We show that the integrated tip-enhanced Raman scattering intensity strongly correlates with the charge state of the quantum dot, and use it to map the electrostatic potential of a single atom. A quantitative equivalence with the established force spectroscopy method is found. We address the underlying photophysical principle of this new method by measuring the Raman spectra as a function of excitation wavelength and the molecular quantum dot charge. We reveal that the observed Raman intensity variations are primarily driven by transitions between resonant and non-resonant Raman scattering regimes of the molecule.
We investigated the structural and magnetic properties of single-crystalline SmCuAs$_2$ using high-resolution synchrotron X-ray diffraction and X-ray resonant magnetic scattering (XRMS) at the Sm $L_2$ and $L_3$ edges. Temperature-dependent diffraction measurements confirm that SmCuAs$_2$ maintains its tetragonal symmetry from room temperature down to 8 K, with lattice parameters showing anomalous behavior below the resistivity minimum ($T \approx$ 30 K). Notably, the \textbf{c}-axis lattice parameter exhibits a plateau and subsequent increase near the N\'{e}el temperature, indicating magnetoelastic coupling. XRMS measurements reveal a commensurate antiferromagnetic structure with a propagation vector \textbf{\textit{q}} = (0, 0, 0.5). Our measurement shows that the Sm moments are aligned within the \textbf{\textit{ab}} plane and arranged in a $++--$ stacking along the \textbf{\textit{c}}-axis. Comparison with related \textit{RE}CuAs$_2$ compounds (\textit{RE} = Pr, Nd, and Gd) suggests that in-plane moment orientation and associated magnetic frustration play a key role in the emergence of the resistivity minimum. Differences in spin-orbit and magnetoelastic coupling across the series highlight their importance in governing low-temperature transport behavior.
Author(s): Saswata Mandal and Chao-Xing Liu
Experimental evidence of spontaneous time-reversal (TR) symmetry breaking have been reported for the superconducting ground state in the transition metal dichalcogenide (TMD) superconductor $4{\mathrm{H}}_{b}\text{−}{\mathrm{TaS}}_{2}$ or chiral molecule intercalated ${\mathrm{TaS}}_{2}$ hybrid supe…
[Phys. Rev. B 114, 094511] Published Mon Aug 17, 2026
Investigating the microscopic mechanisms of quantum materials requires high-resolution scanning probe techniques, often based on atomic force microscopy (AFM). However, implementing AFM in cryogen-free dilution refrigerators with picometer stability is challenged by intense pulse tube mechanical noise ($S_{\rm PT}(f)\approx10^{-6}\,\text{m}/\sqrt{\text{Hz}}$) and the fundamental trade-off with thermalizing piezoelectric motion stages below 100\,mK. Here, we demonstrate an AFM-based scanning microwave impedance microscope integrated onto a standard cold-insertable probe that successfully resolves this bottleneck. By employing a two-pronged design strategy---coupling a mechanically stiff AFM module with a magnetic-field-compatible, critically damped internal spring-suspension---we achieve an extremely low relative tip-sample vibration noise density of $S_{\rm AFM}(f)10^{-11}\,\text{m}/\sqrt{\text{Hz}}$. This yields a spectrally integrated relative tip-sample displacement of $\Delta z\approx10\,\text{pm}$, representing a greater than 100-fold stability improvement over recent fast-loading dry SPM setups. Simultaneously, optimized thermal interfaces, customized copper strapping, and comprehensive RF filtering enable a local sample electron temperature of $T_{\rm e}\leq 60\,$mK, circumventing the thermal penalties of mechanical decoupling. By avoiding permanent structural modifications to the host cryostat, this robust, modular architecture provides an accessible framework for adapting other scanning probe techniques, accelerating the exploration of fragile quantum phases in dry cryostats with picometer stability.
Geometrical design is a crucial and challenging strategy for improving the performance of type-II superconductors, because the proper placement of intended defects in the current path contribute to flux pinning, a reduction in dissipation, and an increase in achievable current density. Topology optimization is currently one of the most powerful approaches used to determine consistent structural geometries. Therefore, a topology optimization approach is presented to inversely design structural geometries of low-temperature type-II superconductors with superconductor-dielectric/vacuum interfaces.
We report structural and physical investigations on the biaxial smectic-A phase exhibited by a compound consisting of asymmetric bent-core molecules. Upon cooling from the isotropic phase, the compound exhibits the following phase sequence: Isotropic (403.9 K) $\rightarrow$ biaxial Smectic-A (359.8 K) $\rightarrow$ Crystal. The polarized optical microscopy, X-ray diffraction, and polarization reversal current measurements clearly establish the biaxial nature of the smectic-A phase without any layer polarization. The measured layer spacing in the entire temperature range of the smectic-A phase is close to the molecular length. The schlieren texture in a homeotropically aligned sample shows both $\pm \frac{1}{2}$ and $\pm 1$ defects which indicate the biaxial nature of this smectic-A phase. The dielectric spectroscopy studies on the samples revealed Debye-type relaxation processes with the relaxation time following the Arrhenius equation with temperature. Interestingly, the observed biaxial smectic-A phase exhibits a remarkable electro-optic response for a planar-aligned sample without any reorganization of the smectic layer structure.
Topological Altermagnetic Insulators Score 0.18
We study the emergence of altermagnetic topological phases stabilized by Ising spin-orbit coupling in a prototypical Lieb lattice model of a correlated altermagnet. Treating the electron interactions within the Hartree-Fock and the exact diagonalization techniques, we establish the co-existence of a quantum spin Hall effect with altermagnetic spin order over a wide region of the parameter space for average electron densities of 2 and 4 per unit cell. We explore how the magnetic structure along edges influences the electronic behavior of the associated topological edge modes, demonstrating their robustness against inversion-symmetry breaking terms.
Author(s): Minghao Zheng, Yu Zhu, Zehua Bi, Yong-Chang Lau, Hang Li, Bei Ding, and Wenhong Wang
The kagome magnet ${\mathrm{Fe}}_{3}{\mathrm{Sn}}_{2}$ has emerged as a key material for exploring topological spin textures, as well as intriguing transport phenomena driven by geometric frustration and spin-orbit coupling. While previous real space imaging studies have extensively characterized th…
[Phys. Rev. B 114, 074423] Published Mon Aug 17, 2026
Author(s): Pritam Das, Subhamita Sengupta, Anjan Jana, Rishabh Duhan, Sulagna Dutta, Arghya Dutta, John Jesudasan, Vivas Bagwe, and Pratap Raychaudhuri
In Type II superconductors, the vortex lattice can exhibit inverse melting, transitioning from a liquid to a crystalline solid as temperature increases. While recently observed via scanning tunneling microscopy in a 20 nm thick amorphous ${\mathrm{Re}}_{6}\mathrm{Zr}$ thin film, this work investigat…
[Phys. Rev. B 114, 094512] Published Mon Aug 17, 2026
We show that the Hodge-de Rham decomposition of the Berry curvature organises the transport of a Bloch band and its fluctuations within a single geometric structure. Splitting the curvature into $L^2$-orthogonal harmonic, exact, and co-exact sectors yields a dictionary for both moments of the current. In the mean response the harmonic sector carries the topological anomalous-Hall conductivity, the exact sector the Fermi-surface geometry and the antisymmetric Berry-curvature dipole of polar metals, and, in three dimensions, the co-exact sector the chiral anomaly, quantised by the Weyl-node charges. In the fluctuations, described by a particle-conserving stochastic Boltzmann equation constrained by the fluctuation-dissipation theorem (FDT), the harmonic sector is silent, so topological transport is noiseless, while the field-driven noise is sourced by the geometric sectors (solely the exact sector in two dimensions); current-noise spectroscopy therefore separates global band topology from local band geometry. We prove that the harmonic null-space protection is dimension-independent, and we settle the remaining sector: the co-exact (monopole) sector carries no conservation law and, under the thermal sampling measure, mixes with the exact sector at $\mathcal{O}(1)$, so it furnishes no clean noise observable. The separation the noise provides is therefore two-way, topology versus geometry, in both two and three dimensions.
Author(s): Lucila Peralta Gavensky, Nathan Goldman, and Gonzalo Usaj
Quantized bulk response functions are hallmark signatures of topological phases, but their manifestation in periodically driven (Floquet) systems is not yet fully established. Here, we show that two-dimensional anomalous Floquet systems exhibit a quantized bulk response encoded in a Chern-Simons axi…
[Phys. Rev. Lett. 137, 086601] Published Mon Aug 17, 2026
Author(s): A. M. Parks and J. V. Moloney
There has been considerable recent interest in the phenomenology of high harmonic generation (HHG) in topological insulators. We study HHG in the Qi-Wu-Zhang (QWZ) model for a Chern insulator, which satisfies spatial inversion symmetry but breaks time-reversal symmetry. The QWZ model is particularly…
[Phys. Rev. B 114, 094301] Published Mon Aug 17, 2026
Author(s): Alban Simonnot, Frédéric Miserque, Jean-Baptiste Moussy, Jean-Yves Chauleau, Michel Viret, and Alain Chartier
Atomistic spin simulations have been used to provide insights into the internal structures of twin (T) and spin (S) domain walls (DWs) in antiferromagnetic NiO. While S DWs imply simple continuous spin rotations, T DWs are composed of a combination of rotations and canting. The hybrid nature of thes…
[Phys. Rev. B 114, 094419] Published Mon Aug 17, 2026
Understanding the physics of doped charge transfer insulators is the most important problem in high-temperature superconductivity. In this work, we show that an in-gap bound state emerges from the localized hole of the doped charge transfer insulator. We propose an approximate ground state wavefunction based on one localized Zhang-Rice singlet and the Neel state. By calculating the excitation states with one hole added and removed from this ground state, we successfully identify the existence of bound states inside the charge transfer gap. This feature is further confirmed by a Lanczos calculation based on matrix product states (MPS) for a system of $4\times4$ CuO$_2$ unit cells. How these bound states evolve into metallic states is further discussed. Our findings identify the key component of recent STM results on lightly doped Ca$_2$CuO$_2$Cl$_2$ and provide a new understanding of hole-doped charge transfer insulators.
The discovery of altermagnetism has initiated intensive research and opened new avenues for spin- tronic and transport applications. While current efforts are mostly focused on bulk materials which are typically insulating, here we propose design strategies to achieve a combination of altermag- netism and metallicity in oxide superlattices by exploiting symmetry breaking, electrostatic doping and confinement. While bulk SrCrO3 does not exhibit altermagnetism due to compensating effects between adjacent layers our density functional theory calculations with a Hubbard U parameter re- veal, that a single SrCrO3 layer confined in a (SrCrO3)1/(SrTiO3)1(001) superlattice (SL) exhibits a sizable non-relativistic spin splitting (NRSS) up to 350 meV with bulk d-wave nature due to the coexistence of orbital ordering and octahedral rotations (OORs). Since this system is insulating, we extend to SrCrO3/LaCrO3(001) SLs. In the (SrCrO3)4/(LaCrO3)4(001) SL the combination of a polar discontinuity at the interface and stronger OORs promotes metallic d-wave altermagnetism. The NRSS of up to 120 meV is contributed by the interfacial Cr d bands at the Fermi level with indications for a spin-selective Fermi surface nesting. These findings establish oxide superlattices as a promising platform to realize and explore altermagnetism for quantum transport and spintronic functionalities
Although interactions are known to generate exotic phases in pseudospin-1/2 flat-band Dirac materials, it remains an open question whether higher-pseudospin Dirac cones continue to govern low-energy interaction-driven orders even without a well-defined valley degree of freedom. Here, we demonstrate a new form of inter-Dirac-cone coherence beyond the valley framework, which is realized through a staggered virtual-loop-current (SVLC) order in a partially filled pseudospin-1 Dirac flat band. Remarkably, the SVLC order continues to be driven by coherence between the pseudospin-1 Dirac cones even after the conventional valley-based description ceases to apply. The virtual loop currents are shown to originate from interaction-driven quantum fluctuations of charge densities and are found to exhibit an alternating circulation between the neighboring triangular plaquettes. The resulting spontaneous time-reversal symmetry breaking induces finite intrinsic anomalous Hall conductivity and orbital magnetization. The SVLC order is shown to be the lowest-energy solution in restricted real-space Hartree-Fock calculations in the weakly interacting regime. Our study establishes inter-Dirac-cone coherence as the organizing principle for interaction-driven orders in higher-pseudospin Dirac systems and identifies these systems as a new platform for driving exotic emergent phases beyond the valley framework.
Author(s): Ruixi Pu, Keqi Guan, Houhao Wang, Dongze Fan, Liangliang Huang, Xiangang Wan, and Feng Tang
Topological materials have attracted immense research interest as a fertile ground for realizing exotic quasiparticles, such as Dirac/Weyl/Majorana fermions. Symmetry plays a vital role in classifying and diagnosing topological states of matter. Among the 230 space groups (SGs), 65 chiral SGs have b…
[Phys. Rev. B 114, 125113] Published Mon Aug 17, 2026
Pretrained machine-learning interatomic potentials, so-called universal or foundation models offer an appealing starting point for atomistic simulations, but their accuracy for material-specific observables often remains limited without additional reference data (fine-tuning). Here, we systematically quantify how much first-principles data are required to convert universal models into ab initio-accurate material-specific potentials, and ask whether fine-tuning is necessarily preferable to training from scratch. We compare five universal MLIP frameworks, MACE-MP-0, SevenNet-0, GRACE-1L-OAM, MatterSim-v1-5M and ORB-v2, across seven chemically diverse systems incorporating rare and reactive events. Fine-tuning on only 10 AIMD-derived configurations is insufficient for the investigated systems; 200 configurations succeed in favorable cases, but the outcome remains strongly system-dependent. By contrast, 2000 AIMD configurations constitute a robust default, yielding low force and energy errors and reproducing the target material-specific observables. Moderately dense sub-sampling of the AIMD trajectory reduces the required trajectory length tenfold with little loss in model quality. Training from scratch on the same datasets is competitive with, and often slightly more accurate than, naive fine-tuning for MACE and SevenNet, whereas GRACE requires more data. The energy profile for a sulfur-vacancy jump in MoS$_2$ reveals that low trajectory-level errors do not guarantee a correct reaction profile, highlighting the need for observable-level validation. Finally, we show that averaging independently trained models improves predictions in scarce-data regimes at no additional first-principles cost. Together, these results provide practical guidelines for converting limited AIMD reference data into reliable material-specific MLIPs for nanosecond-timescale simulations at near-DFT accuracy.
Low-dimensional materials exhibit extraordinary properties that make them promising candidates for advanced technologies. Although they have been investigated extensively, most of the research has focused on layered two-dimensional (2D) materials. Here, inspired by recent advances in atomically thin metallenes, we further reduce dimensionality and use density-functional theory simulations to study the geometry, energetics, elasticity, and electronic structure of 40 non-magnetic one-dimensional (1D) atomic chains of elemental metals. We find that nearly all chains have a buckled ground state, nine chains are distorted, and three chains---Cd, Hg, and Sr---are semiconducting with an electronic gap. We also find that transition metals retain a substantial fraction of their 3D bulk cohesive energy even in 1D chains. We assessed chains' dynamical stabilities by molecular dynamics simulations and found that 26 of them are thermodynamically stable at 100 K. Finally, we performed chain pulling simulations to investigate the straightening dynamics of selected stable chains. Given that experimental techniques have recently reached the 1D-chain limit, our systematic study provides a foundation and timely guide to accelerating synthesis and characterization of these materials.
We present a framework for topological learning based on exceptional point (EP) braiding in a non-Hermitian Bogoliubov-de Gennes Hamiltonian. A closed algebraic equation for the EP super-surface is derived; through momentum quantisation in finite systems, it predicts the exact number and parameter positions of all EPs in real space, irrespective of system size. The EP topology is characterised by two quantised invariants the state-swap fidelity and the normalised Berry phase which cannot both be zero for a topological EP. A complete topological map shows that all EPs lie within a specefic region. Adiabatic encirclements confirm robust state swapping and yield a universal set of braid gates, including Pauli-X, Pauli-Y, Pauli-Z, a Hadamard-like gate, the T-gate, and a SWAP operation, with the special case where a is 0, providing additional phase gates. Building on these generators, we reformulate learning as braid programming a discrete search over the braid group that replaces gradient descent on continuous weights with combinatorial optimisation. A proof-of-concept genetic search successfully discovers short braid words that reproduce the standard Hadamard gate and the H.Z gate with perfect fidelity. This paradigm offers inherent noise immunity, catastrophic-forgetting prevention through compositional concatenation, and guaranteed generalisation by mathematical construction, establishing EP braiding as a promising substrate for robust, interpretable, and topologically protected neuromorphic computation.
Author(s): Ali Ashtari and Ali Khademi
We investigate the topological properties and phase diagrams of a one-dimensional Kitaev chain with spin-orbit coupling, subject to an external magnetic field, and hosting coexisting singlet $s$-wave and triplet $p$-wave pairings. To drive the system out of equilibrium, we introduce a phase in the h…
[Phys. Rev. B 114, 084506] Published Mon Aug 17, 2026
Downfolding ab initio material band structure into a low-energy subspace spanned by orbitals of specified atomic character, a procedure known as Wannier downfolding, is a common task in the simulation of complex materials. We introduce the Intrinsic Wannier Function (IWF) method to Wannierize bands with given atomic character. The method is non-iterative and requires only a single dimensionless parameter to disentangle bands. In benchmarks on silicon, graphene, and the three-band model of a mercury cuprate, we show that Intrinsic Wannier Functions provide high quality downfolded band structures compared to those from standard approaches such as Maximally Localized Wannier Functions and the Selected Columns of the Density Matrix method. Further, their straightforward implementation and robustness positions Intrinsic Wannier Functions as a general and useful tool for Wannier downfolding in materials electronic structure and in high-throughput applications.
Since the seminal experiment by Stankowski et al. [Phys. Rev. B 36, 7126 (1987)] on YBa$_2$Cu$_3$O$_{7-x}$, Magnetically-Modulated Microwave Absorption (MMMA) has become an important technique for detecting the superconducting transition in inhomogeneous ceramic compounds. The rise of microwave absorption below $T_c$ is accompanied by several low-field anomalies, usually attributed to the weak links between superconducting grains showing the Josephson effect, or to the dynamics of Abrikosov-Josephson vortices. In this article, we briefly review selected theoretical models rationalizing MMMA spectra for high-temperature superconductors, focusing on the $3$-dimensional array of Josephson junctions with random parameters including the resistivity, capacity and inductance of each junction, showing characteristic absorption anomalies observed in the experiment. The implications for recently studied microwave absorption in Josephson junction qubits are also discussed.
Author(s): Asaf Farhi and Haim Suchowski
Nanophotonics enables precise control over light–matter interactions, though most established design frameworks for subwavelength nanoparticles rely on isotropic materials. Uniaxial and biaxial particles—common in natural and engineered systems—introduce new degrees of freedom that couple geometry a…
[Phys. Rev. B 114, 115116] Published Mon Aug 17, 2026
Author(s): Peng Wu, Yu-Gui Peng, Qi-Li Sun, Min-Hang Ling, Weiyin Deng, Xue-Feng Zhu, and Zhengyou Liu
Hybrid systems provide a general framework for realizing cooperative effects among multiple topological phases. Unlike the simple coexistence of topological phases in separate band gaps, intrinsic hybridization integrates different topological phases into a single band gap, enabling controlled spati…
[Phys. Rev. Lett. 137, 086602] Published Mon Aug 17, 2026
The development of high-energy-density lithium metal batteries is limited by electrolyte instability and the poorly understood onset of solid-electrolyte interphase (SEI) formation. Here, we use AIMD-trained Deep Potential molecular dynamics to link electrolyte solvation structure to early SEI nucleation in \ce{LiTFSI}/DMC electrolytes. Increasing \ce{LiTFSI} concentration drives the electrolyte from solvent-separated ion pairs toward contact ion pairs and aggregates, with \SI{3.5}{M} showing the strongest anion coordination. This anion-rich environment promotes earlier interfacial Li--F/Li--O bond formation, faster consumption of intact \ce{TFSI-} and solvent, and a denser, LiF/Li$_2$O-rich nascent interphase, in contrast to the more organic-laden, phosphorus/fluorine-based interphase formed by a \SI{1}{M} \ce{LiPF6} reference electrolyte. These results show that bulk solvation architecture biases both the timing and chemistry of early SEI formation and suggest solvation control as a design handle for Li-metal electrolytes.
Nanodiffraction using 4D-STEM has become a key technique for quantitative nanoscale structural mapping in materials research, yet interpreting its high-dimensional datasets in structurally complex materials remains a major bottleneck. Existing analysis workflows typically rely on structural models, manual annotation, predefined classes, or sample-specific heuristics, limiting their ability to characterize heterogeneous complex materials. Here, we introduce DINO4DSTEM, a self-supervised machine learning framework that automatically discovers structurally meaningful states directly from raw diffraction data. Without structural models, manual labels, a predefined number of classes, or system-specific parameter tuning, the framework learns representations that organize diffraction patterns by their intrinsic structural similarities, transforming large collections of low-dose measurements into quantitative nanoscale structure maps. Across diverse datasets, DINO4DSTEM consistently identifies the dominant structural degrees of freedom, providing segmentation without human supervision. We applied the framework to the crystallization of indomethacin, a beam-sensitive, multidomain pharmaceutical system, revealing that crystallinity emerges from a partially ordered precursor and spans a continuous spectrum of structural order. The discovered nanoscale structural states are mapped to reveal the evolution of order across the specimen quantitatively. By replacing task-specific analysis with general self-supervised representation learning, DINO4DSTEM provides a broadly applicable framework for quantitative nanoscale structural mapping in complex materials, enabling the discovery of emergent structural organization in heterogeneous, beam-sensitive systems.
Author(s): Yaomin Ren, Xiyue Cheng, Hanxiang Mi, and Shuiquan Deng
The interplay between band topology and nonlinear optical responses presents a promising platform for discovery, particularly for second-harmonic generation (SHG), which requires broken inversion symmetry. Here, we theoretically investigate the topological constraints on SHG in “essentially noncentr…
[Phys. Rev. B 114, 125309] Published Mon Aug 17, 2026
Semi-metallic noble-metal dichalcogenides are promising materials for infrared optoelectronics, yet the origin and tunability of their nonlinear optical responses remain poorly understood. Here, we demonstrate in-situ mechanical control of photon-drag photocurrents in polycrystalline PtSe$_2$ thin films grown on flexible polyimide substrates. Using polarization-resolved mid-infrared photocurrent spectroscopy under uniaxial tensile strain, we observe pronounced strain-dependent changes in resistivity, photoconductivity, and helicity-dependent nonlinear photocurrents. The spectral response is consistent with optical excitations across the spin-orbit-coupling-induced (SOC) band gap near the K point. We develop a theoretical framework attributing the photocurrent primarily to photon-drag induced by photon-momentum symmetry breaking. Strain modifies its magnitude and polarization dependence through deformation potentials that tune the SOC-induced band gap. These results establish mechanical strain as a route toward reconfigurable infrared polarization detection.
Currently, the fundamental building blocks of leading quantum computers are Josephson junctions, whose core is usually the superconducting Al on Si wafers. However, the transition temperature $T_\mathrm{c}$ of bulk Al ($\sim1.1$ K) is below the boiling point of liquid helium ($\sim4.2$ K), which is one of the challenges to its widespread application. Here, we propose a Si-matched AlB$_2$-type superconductor YSi$_2$ as a promising alternative to Al. The solution of anisotropic (isotropic) Migdal-Eliashberg equation without (with) anharmonicity gives $T_\mathrm{c}\sim20.6$ K ($17.2$ K), which is at the highest level in silicides. Its excellent superconductivity can be attributed mainly to the Si honeycombs, which become plane here due to the 'chemical flattening' effects of the Y atoms instead of being buckled in most silicides. We tested its thermodynamical, kinetic, dynamical, and mechanical stability by first-principles calculations. Particularly, the negative elastic stiffness constant $C_{66}$ calculated by usual methods turns positive even without the zero-point energy once the Si honeycombs are compressed below a threshold. This strain can also make its calculated lattice constants agree with the experimental ones. We propose structures to realize this strain, i.e., YSi$_2$(0001)/Si(111) superlattices, which can also strengthen the overall stability of YSi$_2$ while maintaining its $T_\mathrm{c}$ above $7.0$ K.
arXiv:2308.00439v2 Announce Type: replace-cross Abstract: Recent efforts have demonstrated the first prototypes for compact and programmable photonic quantum computers (PQCs). Utilization of time-bin encoding in loop-like architectures enabled programmable generation of quantum states and execution of different (programmable) logic gates on a single circuit. Actually, there is still space for better compactness and complexity of available quantum states and gate operations: a photonic circuit (PC) can operate at multiple frequencies. Here, we propose an electrically-programmable frequency comb that generates continuously tunable entanglement among different frequencies. The device is not directly integrated into fragile quantum processing components but is to be used as a fast (picoseconds) tunable auxiliary source provided into state-of-the-art measurement-induced loop-based photonic quantum computers employing programmable (50 MHz) beam-splitters (BSs) and phase-shifters. Multimode entanglement generation is controlled via Fano resonance in the nonlinear response. The generated entanglement can be tuned continuously via an applied voltage which can be delivered to the device via nm-thick wires. The proposed device is integrable, CMOS-compatible, and operates below ps but is limited with transistor clock speeds 5-100 GHz.
Although tremendous progress has been made in recent years in the field of polyhydride superconductors, the realization of high critical temperature superconductivity still relies on formidable high pressures. Searching for superconducting hydrides at lower pressures is of particular importance. Here we report the first experimental synthesis of the Mg2RhH6, which achieves superconductivity under a significantly reduced pressure of 30 GPa. The synthesis of Mg2RhH6 proceeds via a two step process (1) preparation of the Mg2RhH5 precursor containing hydrogen atoms stabilized by covalent bonding, followed by (2) hydrogen supplementation resulting in the filling of electrons into anti bonding orbitals above 30 GPa, which was accompanied by the structural transition from RhH5 square pyramid to RhH6 octahedron. Superconductivity is achieved at 30 GPa with a Tc of 24 K, which is further enhanced to 29 K at 53 GPa, evidenced by a sharp drop of resistivity to zero and characteristic suppression of Tc under applied magnetic fields. Our experiments prove the Mg2RhH6 superconductor to be thermodynamically stable above 30 GPa, making it the first case exhibiting a Tc of approximately 30 K at a readily accessible pressure. This study pioneers a highly promising pathway for the rational design and discovery of high temperature superconductors within phonon mediated BCS framework.
This work presents a machine learning-symbolic regression (ML-SR) strategy to develop a physically interpretable formula for predicting low pressure CO2 adsorption capacity in hypothetical metal-organic frameworks (hMOFs). Four ML models were trained on a small dataset of 1,000 samples, and five key descriptors-largest cavity diameter, pore limiting diameter, void fraction, gravimetric surface area, and number of hydrogen atoms-were identified through SHAP and feature importance analyses. Symbolic regression was then employed to derive a concise adsorption formula, Q=aA, where a represents an adsorption baseline (mmol/g) and A is a dimensionless adsorption number incorporating four structural descriptors. We interpret A as the ratio between an adsorption binding force and a diffusion driving force, revealing how pore topology and surface chemistry jointly influence adsorption. Validation against a comprehensive dataset of 137,652 hMOFs demonstrates that this formula achieves over 70% prediction accuracy for 62,448 structures, confirming strong applicability within defined structural and operational ranges. Unlike conventional black box ML models, the proposed physics-guided expression enables efficient prediction and provides clearer insight into adsorption mechanisms.
We determine the distribution of fidelity susceptibility for chaotic eigenstates at the spectral edge of Gaussian random-matrix ensembles. Previous work showed that, in the unitary class, the characteristic susceptibility scale of edge states grows as $D^{1/3}$, rather than proportionally to $D$ as in the spectral bulk, reflecting Airy-edge level rigidity. Extending a determinant-based framework introduced for bulk states, we derive the universal edge distributions for both the orthogonal and unitary ensembles. The two symmetry classes share the scaling variable $g/D^{1/3}$ and exhibit a symmetry-dependent cubic suppression of small susceptibilities, while their algebraic large-$g$ tails reflect the corresponding symmetry-dependent level repulsion. Although eigenvector statistics retain their random-matrix form throughout the spectrum, edge rigidity makes low-lying chaotic states parametrically less sensitive to generic perturbations than bulk states. Our results establish universal, symmetry-dependent spectral-edge fidelity-susceptibility statistics in systems whose chaotic dynamics extends down to the ground state.
Author(s): Madhav Sinha, Thiago Silva Tavares, Hubert Saleur, and Ananda Roy
Topological defects play a fundamental role in the investigation of symmetries in quantum field theories. For conformal field theories in two space-time dimensions, it is possible to construct these defects using lattice models allowing ab initio analytical and numerical computations of their charac…
[Phys. Rev. B 114, 084107] Published Mon Aug 17, 2026
Modern scanning tunneling microscopy (STM) experiments increasingly generate multidimensional datasets that require coordinated data management, visualization, and analysis. We present AngstromPro, an open-source Python-based software platform designed to support these activities within a common interactive environment. Its application architecture organizes inapplication data through independent module instances, each combining a Workspace with a common structure and module-specific visualization and interaction. Scientific processing methods are registered independently of individual modules and operate on explicitly selected inputs through common execution services. A unified I/O subsystem maps heterogeneous ondisk formats to supported in-application data types. The plugin subsystem can add new modules, processing methods, I/O handlers, and in-application data types without modifying the core package. Representative workflows demonstrate the integration of established methods. In the registration example, the normalized cross-correlation maximum increases from 0.855 to 0.966. AngstromPro therefore provides an integrated software architecture for organizing, visualizing, processing, and extending STM data-analysis workflows.
The Altland--Zirnbauer (AZ) tenfold way classifies disordered non-interacting systems by symmetry, but a unified symmetry classification of interacting many-body localized (MBL) phases has been lacking. Here we develop such a classification directly from the emergent local integrals of motion (LIOMs). Our scheme rests on two complementary criteria: whether a symmetry is compatible with a complete LIOM algebra, and whether it enforces many-body degeneracies. These criteria partition MBL phases into stable, fragile, symmetry-protected topological, and unstable classes, and unify AZ classes, onsite Abelian symmetries, and continuous non-Abelian symmetries within a single operator-algebraic framework. Our results provide a systematic foundation for understanding how symmetry constrains the stability and structure of MBL phases.
Entanglement among particles is a defining feature of strongly correlated quantum materials, distinguishing them from conventional metals and semiconductors. The ability to certify intrinsic entanglement among interacting electrons in solid-state materials is important not only for classifying quantum states of matter, but also for developing material-based quantum technologies. Here, we introduce a transport-based protocol for witnessing multipartite entangled electronic states, based on the equilibrium noise spectrum as an experimentally accessible observable. The appropriately integrated, symmetrized, and projected current noise obeys an upper bound that can be derived from microscopic model parameters and is invariant with respect to the choice of electronic basis. We benchmark this framework in several paradigmatic systems, including twisted bilayer graphene, twisted bilayer MoTe$_2$, and Hubbard models, certifying entanglement in the fractional Chern insulating state. The method extends recently developed scattering-based entanglement witnesses to ultralow-temperature materials, where conventional spectroscopic probes are inaccessible but candidate entangled states are expected to arise.
Nested skyrmion bags are composite magnetic solitons whose internal occupation numbers provide an expanded state space for multilevel information encoding. However, deterministic and region-selective writing of individual skyrmions into nested bags remains challenging. Here, using micromagnetic simulations, we propose a field-gated nanocontact protocol for generating and programming double-layer nested skyrmion bags S(m,S(n)). The protocol exploits the opposite field responses of bag regions with antiparallel magnetic backgrounds. Spatially segmented perpendicular magnetic fields selectively expand either the outer region or the inner bag until it overlaps with a nanocontact. A spin-polarized current pulse of the appropriate polarity then nucleates one skyrmion in the selected region, while subsequent field-driven contraction moves the written skyrmion away from the contact and restores the writing site for repeated operation. Starting from an empty nested bag S(0,S(0)), this procedure enables the controlled construction of S(m,S(0)), S(0,S(n)), and general S(m,S(n)) states. The simulated total topological charge changes in unit steps during sequential writing, confirming one-at-a-time and region-selective control. These results provide a possible route toward programmable nested topological states for multilevel spintronic information encoding.
Amorphous hafnia-based films are promising optical-coating materials for cryogenic GW detectors, but their performance depends on how doping and annealing modify the atomic network. We combine grazing-incidence X-ray total scattering measurements with experimentally constrained atomic modeling to study the as-deposited HfO$_2$ and 27% SiO$_2$-doped HfO$_2$ films annealed at 150$^\circ$C and 400$^\circ$C. Pure amorphous HfO$_2$ is a dense, high-coordination network of Hf-centered polyhedra with substantial edge- and face-sharing connectivity. Incorporating SiO$_2$ introduces stable SiO$_4$ tetrahedra, lowers the Hf and O coordination, and replaces highly connected Hf-rich oxygen environments with mixed Si--O--Hf bridges. This produces a chemically mixed network rather than isolated SiO$_2$-rich regions, and shifts the cation topology toward corner-sharing connectivity. Annealing to 400$^\circ$C produces only modest additional structural relaxation. These results provide an atomic-scale description of how SiO$_2$ modifies the topology of amorphous HfO$_2$-based coatings and suggest structural descriptors relevant to understanding their mechanical-loss behavior.
Broadband optical fields can change in both intensity and spectral distribution, but a fixed-response detector maps this evolving information onto a single electrical signal. Here we demonstrate transport-defined photodetection, in which electrical bias selects how photoexcited carriers are redistributed, escape and are collected, creating complementary response functions within one shared active region. In a GaAs/AlGaAs semiconductor ratchet, light-driven ratchet transport defines the response at 0 V, whereas the spectral evolution at -2 V is consistent with field-assisted hot-carrier transport. The overlapping states span a measured spectral range of 0.4-94.5 {\mu}m at 5 K, provide state-dependent calculated detection floors and support joint infrared operation at 30 K. Direct optical beat notes at 7.432 GHz in the mid-infrared and 17.103 GHz in the terahertz demonstrate optical-to-electrical conversion. Their common-path outputs recover an imposed spatial temperature gradient and the transient field-of-view-integrated effective radiation temperature of laser-excited graphite. These results establish post-photoexcitation transport as a function-defining design variable for semiconductor photodetectors, complementing structure-defined, field-tuned and optically encoded approaches to reconfigurable photodetection.
Author(s): Qianli Ma, Brianna R. Billingsley, Alin Niraula, Madalynn Marshall, David A. Dahlbom, Yiqing Hao, Daniel M. Pajerowski, Alexander I. Kolesnikov, Xiaojian Bai, Cristian D. Batista, Tai Kong, and Huibo Cao
We report a comprehensive study on the origin of the enigmatic disordered ground state within the Shastry-Sutherland lattice, ${\mathrm{BaCe}}_{2}{\mathrm{ZnS}}_{5}$, at low temperatures. The magnetization and heat capacity data show a lack of magnetic ordering down to 73 mK. We deploy a localized s…
[Phys. Rev. Lett. 137, 086701] Published Mon Aug 17, 2026
A persistent current switch (PCS) closes the superconducting loop of an MRI magnet; a heater makes it resistive so an external supply can change the magnet current. PCS control is usually treated as binary: heater on--resistive, heater off--superconducting. External current and voltage logs from an MPS2 service power supply (Digit Systems) show for a Siemens MAGNETOM Avanto magnet that the command does not uniquely determine the PCS state: after heater switch-off, Joule self-heating can sustain the resistive state. Purpose-designed maneuvers separate two resistive regimes. With the heater energized, the branch resistance is nearly constant at 1.86--2.19 $\Omega$ below 0.5 V. After switch-off, the self-sustained regime follows $R_{sw}=0.65|V_{node}|^{1.5}$ ($R_{sw}$ in ohms, $V_{node}$ in volts) and is 12-fold below the heater-on resistance at 0.4 V. Both regimes obey one electrothermal relation, $R_{sw}=C(P_h h+V_{node}^2/R_{sw})^a$, with $h$ the binary heater command, over a 690-fold resistance range. First, branch resistance and coil inductance set the redistribution time constant, $\tau=L/R_{sw}$; final-hold duration therefore controls persistent-current accuracy. Across 18 service sessions on other Siemens magnets, analyzed without transferring the Avanto coefficients, the median hold was $13\tau$ and the median residual branch current was 8 ppm of coil current. Second, the intersection of the PCS characteristic and external-circuit load line sets the self-sustainment boundary. The cross-session estimate of 0.062 V lies between observed retrapping at 0.06 V and retention at 0.07 V. In dynamic simulation, the two fixed-coefficient characteristics $R(V,h)$ reduce current RMSE from 1.449 to 0.154 A (9.4-fold); omitting explicit heater input gives no improvement over the inductance-only model.
Machine-learned exchange-correlation functionals correct band gaps at near-semilocal cost, while density-functional tight binding reaches the $10^3$-$10^6$-atom regime; combining them assumes that a better parent yields a better parameterization, but we show it does not. Current-generation functionals are orbital-dependent generalized Kohn-Sham operators, whereas the parameterization channel is built on a multiplicative potential, preventing exact representation. Using the transfer ratio, the surviving fraction of a parent-level change, we find anti-transfer: coherently negative ratios across four covalent semiconductors move the gap in the wrong direction, consistent with a molecular proxy and an r$^2$SCAN control. The minimal-basis overgap is dominated by the on-site convention rather than basis incompleteness; correcting the on-site block removes most of it, while one $d$-polarization shell closes a further $16$-$40%$, depending on the placement of the empty $d$ level, which no free-atom eigenvalue uniquely fixes. Occupied-manifold enhancements, ionic and closed-shell repulsive potentials, and rocksalt-oxide gaps inherit, whereas elemental and III-V covalent networks inherit neither gaps nor repulsive potentials and oxide networks inherit only the latter. We screen 23 elements and release the parameter sets, showing that the transfer ratio provides a cheap pre-test before any parameterization campaign.
Higher-form symmetries generalize conventional global symmetries and act on lower-dimensional submanifolds of a quantum system. While Abelian topological phases can be organized by 1-form symmetries that form a group, non-Abelian topological phases based on finite groups require 1-form symmetry operators governed by non-invertible fusion algebras. In this work, we make this statement precise in quantum double lattice models $\mathcal D(G)$ for finite non-Abelian groups $G$. We construct the electric, magnetic, and dyonic 1-form operators directly at the lattice fixed point and show that together they form a complete nonlocal diagnostic algebra for the topological Hilbert space. Using these operators, we explicitly determine the cylinder and torus ground-state subspaces for arbitrary finite $G$. Furthermore, we calculate the microscopic fusion and gluing of the 1-form symmetries and show that their topological deformation properties emerge after projection to the defect-free topological subspace. Our results establish ground states of non-Abelian quantum double models as a concrete microscopic realization of spontaneous non-invertible 1-form symmetry breaking and provide an operator language that may be useful for characterizing such states in quantum processors.
The optical response of magnetic materials is conventionally classified through magnetic space groups (MSGs), where spin and lattice are locked by the relativistic spin-orbit interaction. However, most optical observables are governed primarily by nonrelativistic physics, and thus a purely MSG-based description can overlook important insights. Here we systematically show that spin-space groups (SSGs), which operate at the nonrelativistic level, provide a broader and more predictive framework for analyzing a variety of optical responses of magnets. Focusing on linear optical absorption, we derive the transformation rules imposed by SSGs and show that they generate effective real-space point groups, which can enforce relations among charge response coefficients that are absent from conventional MSG analysis. We illustrate the basic principle in a Lieb-lattice altermagnet model with tunable spin-orbit coupling, where SSG predictions on the linear dichroism remain remarkably accurate even when relativistic band splittings become sizable. We further establish the predictive power of this framework through first-principles calculations on two altermagnetic candidates: the actinide UCr2Si2C, where the optical absorption remains nearly isotropic despite its strong spin-orbit coupling and the pronounced anisotropy apparent from magnetic symmetries, and the transition-metal fluoride RbMnF4, where birefringence is confined to a single plane by symmetries emerging exclusively from SSGs. Finally, we extend the concept to the spin Hall response of the coplanar noncollinear antiferromagnet ScMnO3, where SSGs explain the hierarchy of calculated spin Hall coefficients, demonstrating their direct relevance to spintronics as well.
Molecules that absorb and emit light play a central role in microscopy, light-emitting devices and photosynthesis. Their fluorescence arises from well-defined radiative transitions that are governed by the electronic states and their coupling to the nuclear motion that are influenced by the local environment. Yet the effect of controlled atomic-scale variations in the emitter surroundings remains unexplored. Here, we use scanning tunneling microscopy combined with optical spectroscopy to investigate the optical response of a single phthalocyanine to the change in the position of a nearby molecule, controlled with precision better than 100 pm. Upon decreasing the intermolecular distance, the molecular emission energy redshifts and its line profile evolves. Supported by theoretical calculations, we disentangle the electronic and nuclear contributions to the changes in fluorescence. We find that the redshift originates from the interaction between the excitations of the two molecules, while the lineshape changes reflect modifications of the molecular rotational degree of freedom and non-equilibrium dynamics. We extend this control to larger assemblies, where one molecule tunes the energies of two chromophores, mimicking the environmental tuning in photosynthetic systems. Our study provides atomic-scale insight into how the local environment affects the optical properties of molecular systems.
Quantitative spintronics increasingly depends on a handful of GPU micromagnetic codes, all of which require NVIDIA hardware and single precision throughout, leaving researchers without such hardware unable to run even the standard validation problems. We report Claude-SpinDynamics (Claude-SD), a new open source micromagnetic simulator with a cross platform C++20 core (Windows and Linux) and a Python interface that closes this gap: a complete CPU build, validated by the same test suite as the GPU path, runs every unit test and uMAG standard problem with no accelerator at all, alongside GPU builds offering both single and double precision, a choice of two demagnetization FFT backends, and natively implemented spin-orbit, spin-transfer, and Zhang-Li torques, Dzyaloshinskii-Moriya interaction, and percell materials.Claude-SD natively interprets mumax3's .mx3 scripting language, so existing community scripts run unmodified; under matched conditions the two codes agree cell-by cell to single-precision round-off, and, together with mumax+ and OOMMF, to within 2% on the uMAG dynamic-switching standard problem, with MuMax-CO agreeing to mumax3 to float32 round-off on the same problem. Benchmarked head-to-head against these three codes, Claude-SD's single-precision build is the fastest solver on small and two-dimensional problems and remains competitive at the largest grid sizes, while its double-precision and dual-FFT-backend paths are unmatched among GPU micromagnetic codes. A GPU replicabatching extension further advances an entire ensemble of finite-temperature trajectories in a single kernel launch per step, giving one to two orders of magnitude of throughput over a per-trial loop while reproducing single-trajectory results to numerical round-off. The complete source is openly licensed and distributed with runnable example notebooks and documentation for independent reproduction.
Colloidal gels are frequently modeled as monodisperse particle networks, although practical formulations commonly contain particles with multiple characteristic sizes. Here, we use large-scale, hydrodynamically resolved simulations of colloidal depletion gels to isolate the effects of particle size and local packing in bimodal systems with a small-to-large size ratio of 1:2. Increasing the large-particle fraction introduces new heterotypic angular motifs and substantially increases the fraction of bonds participating in tetrahedral structures, with a maximum at intermediate composition. However, these additional rigid motifs do not reorganize into larger or more highly connected tetrahedral aggregates. The mean coordination and characteristic aggregate size remain nearly composition independent. By contrast, the void and cluster-size distributions coarsen systematically as the large-particle fraction increases. These mesoscale distributions largely collapse when normalized by a composition-dependent particle length scale, indicating that changes in composition primarily rescale gel architecture rather than producing distinct rigid-network topologies. An elastic modulus estimated using Cauchy-Born theory similarly follows this effective length scale more closely than the abundance of local tetrahedral motifs. These results show that, for moderate size disparity, particle size controls the structural scale and predicted mechanical response of bimodal colloidal gels more strongly than enhanced local packing.
A flexible body placed in a steady flow bends to reduce drag. This self-streamlining is a hallmark of fluid-structure interaction (FSI). Granular-structure interaction is equally ubiquitous in nature. However, it remains poorly understood. Thus, we investigate inertial granular-structure interaction (IGSI). Specifically, ejection induced by a flexible plate sweeping a granular bed is experimentally examined. We find that a faster sweep results in less ejection, particularly for a flexible plate. To understand the underlying physics of this behavior, a dimensionless number Sk is introduced as the ratio of the plate elastic timescale to the sweep timescale. At $\mathrm{Sk} \lesssim 1$, the plate deflection follows the self-streamlining law of FSI and induces substantial ejection. At $\mathrm{Sk} \gtrsim 1$, on the other hand, the plate skims the bed and the mass of ejected grains decreases sharply. Sk organizes IGSI as the granular counterpart of FSI.
Indentation experiments can be used to mimic real-life damage events of glasses that lead to surface flaws and thus lower practical strength. Conventional indentation studies often focus on the surface deformation after unloading. However, to understand the link between the surface deformation and structure, it is crucial to characterize the sub-surface deformation during the indentation process. The indentation-induced deformation, consisting of both elastic and plastic zones, is governed by the glass composition and structure, indentation and atmospheric conditions, and stress state. However, only a few experimental methods exist for characterizing the sub-surface indentation deformation mechanism during indentation. In this study, we use synchrotron X-ray nanoscattering to probe the deformation mechanism in situ during indentation of four types of oxide and oxynitride glasses with distinct structural features. This is done by measuring the variation in the position and intensity of the first sharp diffraction peak of the X-ray structure factor with a high spatial resolution down to ~100 nm. We find that the deformation zones of these glasses, which are characterized by the shape, size, and relative contribution between densification and shear flow under different indentation loads, vary with Poisson's ratio. Thus, our work provides new insights into the mechanical behavior of oxide glasses, contributing to the design of more damage-resistant glasses.
The effective mass approximation is widely used across models of carrier transport, optical response, and excitons in semiconductors and insulators, but its validity hinges on the assumption that the band dispersion $E_n(\mathbf{k})$ at the relevant extremum is analytic. We prove that analyticity holds at any non-degenerate extremum for Kohn-Sham density functional theory (DFT) with local or hybrid exchange-correlation functionals, for Hartree-Fock, and for band-edge $G_0 W_0$ quasiparticle energies in gapped systems. Band non-analyticity (or warping) in these settings is therefore intrinsically tied to degeneracy. We then use group theory to determine the symmetry-allowed form of the effective mass tensor for each of the 32 crystallographic point groups, providing a stringent consistency check on first-principles calculations. As a representative application, we show that the electron and hole effective masses at the $K$ point of monolayer MoS$_2$ must be strictly isotropic at the DFT and $G_0W_0$ levels.
High-lying Rydberg excitons in two-dimensional semiconductors universally exhibit a characteristic odd-integer energy scaling distinct from three-dimensional systems. While this hallmark of two-dimensional Coulomb interaction is well known from quantum mechanical solutions, its deeper classical geometric origin remains unclarified. Here we show that the complete bound-state spectral structure of the two-dimensional Coulomb problem---a central model for two-dimensional exciton physics---follows as an exact theorem from classical mechanics augmented by a single phase-scale parameter $\alpha$ with dimensions of action. We derive an amplitude-closure criterion as a necessary and sufficient condition for a classical propagator kernel to satisfy a linear evolution equation, and demonstrate that the singular Coulomb potential can be mapped shell-by-shell via Levi-Civita regularization into the class of quadratic Hamiltonians that obey this criterion exactly. The resulting spectrum bears odd-integer modal numbers, $1/N^2$ energy ratios and $N$-fold degeneracies, all independent of $\alpha$ and consistent with experimental observations of high-lying Rydberg excitons. This work provides a pure classical-geometry benchmark for two-dimensional exciton spectral analysis, allowing quantitative disentanglement of universal Coulomb effects from material-specific screening effects. No semiclassical, short-wavelength or $\hbar \to 0$ approximation is invoked at any stage. Our results invert the usual logical hierarchy for this integrable system: the wave equation emerges as a representation of the underlying classical geometry, rather than as an independent first principle.
Physical reservoir computing is a promising approach for fast and energy efficient computer vision, natural language processing, and general pattern recognition. This work presents a physical reservoir based on magnonic-optoelectronic oscillator (MOEO). This approach allowed us to realize short-term memory and nonlinearity as separate system components. The device`s optical path uses a fiber-optic delay line as a short-term-memory element. The microwave path is responsible for nonlinear mapping of input data to a higher-dimensional space. The strong four-wave nonlinearity of spin waves propagating in an yttrium-iron garnet (YIG) ferrite film enables the process. The reservoir performance is evaluated by completing task-independent tests known as short-term memory (STM) and parity-check (PC) tasks. In addition, a numerical model of the MOEO based reservoir is developed. Results of the numerical simulation of the reservoir performance are in good agreement with the experimental data.
A class of monitored topological invariants compares ordinary and symmetry-twisted quantum trajectories with identical stochastic records, so direct estimation requires exponentially costly matched-record postselection. We replace the twisted quantum experiment by uniformly randomized symmetry eigenstates with known charges, ordinary-boundary monitoring, and an offline twist decoder. Their correlation yields an exact finite-time response identity and removes this experimental sampling bottleneck. When the ordinary charge sharpens and the ordinary-to-flux deformation has trivial net readout-character flow, the response converges to the projective commutator of the symmetry-protected-topological phase; generator-pair responses then determine its finite-Abelian cohomology class. Spectator-sector crossings may close the global Lyapunov gap without changing this character-valued response. In monitored cluster circuits, the decoder is exact and polynomial in the Gaussian limit, while Gaussian-drop reconstruction treats interacting records; independent joint-sector spectroscopy and effect-state diagnostics validate the topological deformation.
Topological charge pumping is paradigmatically understood through two-band systems such as the Rice-Mele model, which are intrinsically restricted to a single independent pumping channel. In this work, we introduce the Trimer Thouless Pump (TTP), a minimal three-band generalization that exhibits genuinely multigap topological transport. By subjecting a one-dimensional three-site lattice to cyclic adiabatic modulations of its hopping amplitudes and antisymmetric onsite potentials, we explore a topological regime characterized by two independent bulk gaps. We show that the quantized charge transport is driven by highly localized Berry curvature hotspots corresponding to effective two-level Dirac avoided crossings on the parameter torus. Crucially, we demonstrate that the middle energy band acts as a geometric mediator: it facilitates the exchange of quantized Berry flux between the upper and lower bands while maintaining a net zero Chern number itself. This bulk topology is corroborated by the spectral flow of boundary-localized edge states traversing multiple gaps. Furthermore, we map the topological phase diagram as a function of central-site detuning, illustrating a band-selective transfer of topological invariants across discrete phase transitions. Finally, we propose a concrete experimental protocol to realize the TTP and observe its multigap charge transport using ultracold atoms in phase-controlled optical superlattices.
We construct the natural generalization of stochastic quantization (in the Markovian sense) by considering jump-diffusion processes. This class of stochastic processes exhibits non-continuous paths, so-called L\'evy flights. In the presence of jumps, action landscapes with barriers can be efficiently explored, improving and even restoring ergodicity where traditional diffusion approaches become inefficient. We explore different strategies for constructing efficient jump updates, which we deploy to address the benchmark problem of topological freezing in 2d U(1) gauge theory.
Different field species can begin with finite anisotropic propagation geometries whose principal axes need not coincide. We ask whether local Yukawa interactions on a finite graph can nevertheless generate one common infrared spatial cone, even when the interactions that drive the locking become marginally irrelevant. Retaining the full finite mismatch between positive-definite spatial kinetic matrices, we derive the one-loop nonlinear matrix flow and show that its Thompson diameter is globally nonexpansive. On a connected graph, persistent normalized edge activity upgrades this to a uniform finite-window contraction, so all interacting sectors asymptotically share one relative propagation geometry. An explicit two-channel Pauli-Dirac Yukawa-quartic completion realizes the persistence conditions on an open weak-coupling set of finite-mismatch initial data. In four dimensions the Yukawa couplings vanish in the infrared, yet their accumulated interaction time diverges, leaving a Gaussian endpoint with a common spatial cone. For a controlled two-plateau extremal class, graph distance also fixes the first nonzero short-time order of the diameter decrease. Thus a common cone can be collectively selected by renormalization-group dynamics rather than imposed as a microscopic common structure.
We investigate the conditions under which momentum-dependent similarity transformations preserve spectral properties of lattice Hamiltonians with open boundary conditions (OBC). While such transformations exactly preserve spectra in infinite systems, their application to finite systems introduces subtleties due to the long-range nature of the inverse transformation in real space. For general traceless $2\times 2$ Hamiltonians, we derive necessary and sufficient conditions for reduction to skew-diagonal form via constant similarity transforms, providing explicit transformation matrices for all cases. We then establish rigorous conditions for bulk spectral preservation under momentum-dependent transformations: the generalized Brillouin zone of $H$ must lie inside the smallest zero of $\det S(z)$ (the two-radius condition $r_{\mathrm{GBZ}}^{\max}z_{\min}$), together with a spectral-stability (no critical non-Hermitian skin effect) condition on $H$. Two-sidedness of $S(z)$ governs only the modification of a finite number of boundary eigenvalues, not the bulk. Our results establish when bulk topological invariants computed in transformed coordinates reliably predict boundary physics, with implications for non-Hermitian systems, photonic crystals, and other platforms where chiral or hidden symmetries emerge only after appropriate basis changes.
We demonstrate optical coherence tomography (OCT) as a measurement technique for dense, optically opaque suspensions. Conventional optical methods cannot access the interior of such suspensions. OCT resolves individual potato-starch particles (${\sim}20~\mathrm{\mu m}$) as distinct scatterers, even though the suspension appears opaque to the eye. By tracking the vertical centroid position of the particle-laden layer $\langle Z \rangle(t)$ and the supernatant boundary $Z_\mathrm{sup}(t)$ in the same OCT image sequence, we obtain the instantaneous settling velocity $V(t)$ and the time-evolving effective volume fraction $\phi_\mathrm{eff}(t)$ simultaneously and continuously in time. To our knowledge, this is the first measurement to combine settling velocity and particle concentration into a single continuous trajectory within one sedimentation run. Conventional batch measurements yield only one velocity value per run. We applied this method to dense potato-starch suspensions, varying the initial volume fraction $\phi_0$ from 0.30 to 0.50 and the solvent density $\rho_\mathrm{L}$ from 1.0 to $1.3{\times}10^3~\mathrm{kg~m^{-3}}$ using aqueous sodium polytungstate solutions. The normalized velocity $V/V_\mathrm{Stokes}$ plotted against $\phi_\mathrm{eff}$ collapses onto a common trend consistent with both the Krieger--Dougherty model and the Richardson--Zaki law over $\phi_\mathrm{eff} \simeq 0.30$--$0.52$, confirming that the method captures physically reasonable hindered-settling behavior. These results establish OCT as a viable tool for probing internal dynamics in dense suspensions that were previously inaccessible to optical measurement.
We present a Maxwell-Demon nonequilibrium molecular dynamics method for measuring the shear viscosity of a Lennard-Jones fluid. The simulation cell is divided into two regions of width $w$ in the $x$-direction, with particles free to move between the two sides. The Demon maintains equal and opposite regional average particle velocities in the $y$-direction ($\pm u_p$), by applying an acceleration $g_{total}$ that includes both total force balance and a correction for diffusion of particles across boundaries. The momentum relaxation rate needed to sustain the nonequilibrium steady state (NESS) is $\gamma=g_{total}/u_p$. We show that the driven velocity profile is not imposed point-wise in $x$ by the constraint, but is selected by the regional hydrodynamic response of the fluid. For this shear geometry, the measured NESS profile in Eulerian slabs is well represented by a piecewise parabolic form, reminiscent of planar Poiseuille flow. The parabolic profile estimates the kinematic viscosity from work done on the shearing fluid, $\nu_{para}=\gamma_{total}w^2/12$, as well as an entropy production estimate, derived from heat removal by the Nos\'e--Hoover thermostat that keeps each regional average temperature constant. For a representative run, the work and entropy routes agree to within $0.6\%$, confirming consistency between the mechanical work supplied by the Demon and the heat removed by the thermostat. Once NESS driving is removed, the parabolic velocity profile relaxes exponentially rapidly to sinusoidal, the natural transverse momentum-diffusion eigenmode. These results establish the Maxwell-Demon shear method as a direct NEMD route for obtaining shear viscosity from momentum diffusion, work, and entropy balances. Our results in 3D for increasing system size $N$ (the number of particles) demonstrate that shear viscosity approaches an asymptote (the hydrodynamic limit) as $1/\sqrt{N}$.
We study the quantum correction to the conductivity due to disorder in two-dimensional fragile topological bands with nonzero Euler class. Contrary to graphene where two Dirac nodes have opposite vorticities, two bands with a unit Euler number possess two Dirac points with the same vorticity, which may affect the Anderson localization. Most notably, we report an anomalous localization behavior in spinful magnetic Euler bands based on symmetry analysis and diagrammatic calculations. Despite the presence of spin-orbit coupling and an in-plane magnetization that explicitly breaks physical time-reversal symmetry, the system exhibits weak localization behavior characteristic of the orthogonal symmetry class. We demonstrate that this counter-intuitive phenomenon originates from an emergent effective time-reversal symmetry composed of crystalline and spacetime inversion symmetries, allowing it to supersede the standard localization behavior. Our findings reveal that the effective crystalline symmetries can fundamentally alter the universality class of disordered systems, rendering the localization behavior independent of the specific vorticity configuration of Dirac nodes.
This paper demonstrates that ordinary fermions, interacting via a BF mediator, form a renormalized structure with non-trivial topological properties. We explore the analogy between the renormalized fermion and a subset of real three-dimensional topological insulators (TIs) in the vicinity of their single Dirac cones. Using the typical magnitude of TI lattice and gaps, we constrain model parameters. The topological structure induced by radiative corrections enters a class of modified Dirac equations, ensuring the existence of helical gapless near-boundary modes. We derive an effective potential for inter-quasi-particle interactions that incorporates finite-size effects in the axial direction, revealing signatures of spin-orbit coupling and time-reversal invariance. Remarkably, particles with different spins do not interact via the characteristic spin-orbit coupling, and a non-central spin-dependent force arises. We also address the behavior of the system in the phase transition associated with the thin-film limit.
Protontherapy precision depends on accurately knowing the stopping power of liquid water, as it is the most abundant component of soft body tissues. Difficulties when working with volatile liquids have led to a long-standing debate regarding the values of the stopping power and the mean excitation energy $I$ of liquid water. The equivalence between the stopping power of liquid water and amorphous ice per unit mass density across all clinically relevant proton energies opens the possibility to obtain a reliable estimation of the $I$-value of liquid water. In this work, we employ two complementary theoretical methodologies to assess the proton stopping power of water. The MELF-GOS (Mermin Energy Loss Function - Generalized Oscillator Strengths) approach, based on the perturbative dielectric formalism, serves as an accurate reference for sufficiently high energies, while the novel non-perturbative TDDFT-Penn (time-dependent density functional theory - Penn) method ensures accuracy for energies even below the stopping maximum. These stopping-power values were incorporated into the simulation code SEICS (Simulation of Energetic Ions and Clusters through Solids) to evaluate proton Bragg curves from $1$ to $230$ MeV. Comparisons with available precise depth-dose measurements provide critical insights that help establish the consistent value $I = 79.4$ eV for liquid water, providing robust physical grounds for improving range prediction for treatment planning.
Evolving crack fields in structural health monitoring and fracture assessment must often be inferred from sparse mechanical measurements rather than dense full-field observations. We develop CNN2D--ConvGRU, a convolutional-recurrent framework for measurement-conditioned reconstruction of time-dependent phase-field brittle fracture. At each load step, the model maps a fixed-length history of phase and displacement fields and sparse current-step displacement measurements to the current full-field state. New measurements are assimilated during sequential deployment, making the framework a state-inference surrogate rather than an autonomous time integrator. It reproduces crack paths, damage evolution, and bulk displacement response, with the largest errors near propagating crack tips and steep displacement gradients and some drift at late stages. Without retraining, weights learned on a $256 \times 256$ raster are evaluated on a $512 \times 512$ raster of the same physical domain and finite-element discretization using a proportionally refined measurement grid. This empirical raster-and-sensing transfer preserves the principal damage topology and global damage evolution, although fine-scale displacement errors increase near crack tips. Comparisons with alternative spatial and temporal architectures show that CNN2D--ConvGRU offers a favorable balance between reconstruction accuracy and computational cost. Relative to repeated finite-element solutions, sequential reconstruction achieves mean speedups of $175\times$ on CPU and $253\times$ on GPU. These results demonstrate efficient full-field fracture-state reconstruction from sparse observations while retaining the spatial structure and history dependence of phase-field fracture.
Fractionalizing a quantum two-level system is usually associated with encodings based on pairs of Majorana fermions---an operational fractionalization. We show an alternative algebraic fractionalization by embedding Sz\'{e}kely's classical ``half-coin'' into a non-Hermitian Krein space. The coefficients of $(q+pz)^{1/2}$ define a signed sequence and a normalized, non-Hermitian biorthogonal operator describing a biorthogonal half-qubit. We prove that two such objects fuse into an arbitrary pure qubit through the signed Vandermonde convolution that the collective $N\ge2$ vectors are null in Krein space. $L_1$ norm of the half-qubit follows in closed form, $\lVert p\rVert_1 = 2\sqrt{q}-\sqrt{q-p}$. Its $L_1$ norm increases monotonically with the bias and attains its supremum $\sqrt{2}$ precisely at the unbiased point $p=q=1/2$. Interestingly, we identify two structural results as follows. First, number parity and the $\eta$-metric generate a distinguished commuting $\mathbb Z_2\times\mathbb Z_2$ subgroup. Second, we find the $\eta$-metric obstructs any local $\eta$-self-adjoint partner of the parity, so a half-qubit carries a $\mathbb{Z}_2$ observable but no local $SU(2)$. The full Pauli algebra emerges only upon fusion. We then show that the construction survives truncation of the Fock basis: the fused qubit is exact at every cutoff, and the Vandermonde cancellation is visible in sign-weighted photon-number statistics, and can be tested using existing cavity and trapped-ion state-synthesis methods. Finally, we generalize this algebraic fractionalization to a $1/n$-qubit, which can be achieved by replacing the square root with an $n$th root.
Sample-based quantum diagonalization (SQD) and quantum-selected configuration interaction (QSCI) are the electronic-structure methods with most hardware traction, yet their canonical target -- the ground-state energy -- is where classical methods have caught up. We move the target to dynamics and the resource question. From one bitstring-sampling primitive -- computational-basis measurements of a shallow real-time circuit, with no Hadamard or controlled unitaries -- we reconstruct, from sampled subspaces, the single-particle spectral functions $A(\omega)$ and $A(k,\omega)$ and the neutral-sector dynamical structure factors $S(q,\omega)$ and $S^{zz}(q,\omega)$, each built classically in the Lehmann representation from its own subspace. The reconstruction matches exact diagonalization on Hubbard chains and, for $A(\omega)$, across nineteen molecules (FCI-verified to $10^{-5}$ Ha), and runs on the IBM Heron processor. Second, we ask which resource controls the cost -- the determinant support $|\mathcal{S}|$ the sampler must populate. On number-conserving states the fermionic AntiFlatness collapses to one 1-RDM invariant, $\mathcal{F}_1 = 4\,\mathrm{tr}[\gamma(1-\gamma)] = 2N_u$. An orbital-rotation (Gaussian) invariant while $|\mathcal{S}|$ is basis dependent, $\mathcal{F}_1$ is provably decoupled from the cost; the cost is instead lower-bounded and tracked by the entanglement -- the minimal bond dimension $\chi$ (Spearman $\rho = 0.90$). One-body magic is thus a faithful multireference diagnostic but an unreliable cost predictor; any genuine advantage lives in the non-Gaussianity of the higher-body cumulants. We prove moment exactness and a sampling bound polynomial in $|\mathcal{S}|$, independent of Hilbert-space dimension. Self-consistent configuration recovery improves the subspace under device noise, while a learned generative model does not beat that classical baseline.