arXiv subjects

Di Xiao

Publications and source records attributed to Di Xiao.

At least 19 recordsLinked to original sources

arXiv2026

HyperDet Wavefunction: A Phase-Agnostic Ansatz for Strongly Correlated Systems

Competing phases of strongly correlated systems are often described by trial wavefunctions built on phase-specific assumptions. We propose the \emph{hyperdeterminant (HyperDet) wavefunction} as a phase-agnostic ansatz for both bosonic and fermionic quantum many-body systems exhibiting spontaneous symmetry-breaking, fractionalization, and/or topological order. The HyperDet structure emerges by fusing auxiliary fermionic parton Slater determinants into physical orbitals through a learnable \emph{fusion tensor $\mathcal F$}. Optimized using variational Monte Carlo, a single HyperDet architecture achieves overlaps exceeding $99.9\%$ with exact-diagonalization ground states for nearly all sampled parameters across fractional Chern insulator (FCI) phases and their neighboring competing phases in both bosonic and fermionic models. Beyond its variational expressiveness, the optimized fusion tensor also provides rich interpretability. We show that, (i) the singular-value spectra of the \emph{bipartite fusion matrix} can be used to track phase transitions; (ii) the reconstructed Bott indices reproduce the parton Chern numbers expected for the FCI states without parton-Hamiltonian input; and (iii) faithful lifts of physical translations to the parton degrees of freedom recover the expected translation fractionalization in the bosonic FCI without projective symmetry class assignment. These results establish HyperDet wavefunction as a promising framework for both variational ground-state searches and phase-diagram explorations across strongly correlated phases, and for providing theoretical insights by connecting the optimized wavefunction with parton microscopics and field-theory descriptions.

cond-mat.str-el↗

arXiv2026

Haldane-Holstein model at fractional filling: Route to bosonic fractional Chern insulator and quantum anomalous Hall crystal

Electron-phonon coupling is generally expected to suppress band topology, driving a topological band insulator into a trivial phase. Here we show that, using the prototypical Haldane-Holstein model at partial filling of a topological band, strong electron-phonon coupling can instead stabilize topological phases of matter. The electron-phonon coupling plays a double role: it generates the longer-range interactions that correlate the carriers and, in the attractive channel, also binds them into bosonic pairs. For spinful electrons, it pairs opposite spins into charge-$2e$ bipolarons that form a bosonic fractional Chern insulator (FCI) at filling $ν=1/2$ with charge-$e$ semionic excitations. Tuning the band topology and the coupling strength maps out a rich phase diagram containing this bosonic FCI, superconductors condensed at the $M$ and $K$ points, and several charge-ordered solids. For spin-polarized electrons, strong coupling instead stabilizes a $C=2$ quantum anomalous Hall crystal (QAHC) at $ν=1/3$. Electron-phonon coupling thus emerges as a route to, rather than an obstruction against, topology in partially filled Chern bands.

cond-mat.str-el↗

arXiv2026

Multi-scale Memory and Regime Shift in the Hyperactive Repeating FRB 20240114A

We present a statistical analysis of FRB~20240114A, a hyperactive repeating fast radio burst, based on 11,553 bursts detected by FAST over 214 days. Our main findings are fourfold. (1) On the most active day (MJD~60381, 3,197 bursts in 4.38 hr), event-rate coherence analysis reveals persistent correlated activity extending up to 3600~s, the longest reported for any repeating FRB, showing memory persists even in intense bursting epochs. (2) The waiting-time distribution on this day is well described by three exponentials, whereas the full 214-day sample develops a threshold power-law tail, indicating burst statistics depend on the observational baseline, with long-range correlations emerging only over longer timescales, a hallmark of self-organized criticality. (3) Rescaled range (R/S) analysis of waiting times reveals a broken power law, with Hurst exponents $H_1=0.63\pm0.02$ (short-lag weak memory) and $H_2=1.04\pm0.02$ (long-lag non-stationary drift). The break corresponds to $\sim$1 hour, consistent with the 3600~s coherence limit. R/S analysis of energies similarly exhibits a break ($H_1=0.60\pm0.01$, $H_2=1.10\pm0.05$) at a different lag, reinforcing that non-stationarity affects both temporal and energetic properties. (4) Energy distributions exhibit waiting-time-dependent slopes that are consistent with the full and daily samples, and the high-energy cutoff remains constant across waiting-time groups, suggesting that the maximum energy scale is an intrinsic source property. Together, these results establish a multi-scale memory framework: the source behaves stochastically on short timescales but exhibits systemic non-stationarity over months, providing benchmarks for burst models and highlighting the need for long-term, high-cadence monitoring to capture temporal complexity.

astro-ph.HE↗

arXiv2026

Tunable Multiband Geometry and Fractional Phases in Higher Vortexable Systems

Higher vortexability is often viewed as a route to topological flat bands with higher-Landau-level-like quantum geometry. Here we emphasize a complementary perspective: it provides a tunable multiband structure in which wave function geometry can be varied continuously while the band dispersion, degeneracy, and topology remain fixed. We perform systematic exact-diagonalization studies of many-body phases in fractionally filled higher vortexable moiré systems, retaining the full flat-band Hilbert space rather than projecting onto a single band. The multiband treatment reveals a cascade of Abelian and non-Abelian phases at zero magnetic field, including integer and fractional exciton insulators, Abelian fractional Chern insulators, Moore-Read and Read-Rezayi states. At fixed filling, different phases are connected through transitions or crossovers driven solely by changes in wave function geometry, highlighting quantum geometry itself as a direct tuning parameter between competing topological states. At fillings associated with Moore-Read and Read-Rezayi states, our calculations show that interband mixing shifts the optimal quantum geometry regime without suppressing non-Abelian topological order under screened Coulomb interaction. Our results establish higher vortexable moiré bands as a tunable platform for exploring geometry-driven multiband topological phases at zero magnetic field.

cond-mat.str-el↗

arXiv2026

Topological Charge-Transfer Excitons

Excitons possess internal structure absent from single-particle Bloch particles, allowing their band topology to emerge from the bound-state structure rather than being inherited from their constituents. This raises the question of how the internal structure of a bound state can provide a microscopic origin of exciton topology. Here we show that the real-space embedding of charge-transfer excitons can generate an intrinsic manifold of symmetry-related off-site composite orbitals whose coupling supports topological exciton bands. Lateral electron-hole separation embeds the localized exciton on the bond connecting its constituent sites rather than on either site. We demonstrate this mechanism in a honeycomb lattice, where three bond-centered charge-transfer exciton orbitals form a Kagome lattice. By solving the Bethe-Salpeter equation, we show that this emergent multi-orbital manifold supports a topological exciton flat band upon time-reversal symmetry breaking, even when the electron and hole bands are topologically trivial. The resulting band exhibits nearly uniformly distributed quantum geometry, favorable for interaction-driven bosonic states. Our results establish a general route toward topological bands of localized composite bound states and unconventional strongly correlated bosonic phases.

cond-mat.mes-hall↗

arXiv2026

Submillimeter Detectability of Gravitational-Wave Counterparts from Neutron-Star Mergers with the Xue-shan-mu-chang 15-meter Telescope

Submillimeter (sub-mm) follow-up of binary neutron star (BNS) mergers provides unique constraints on the early-time energetics and environments of relativistic outflows, capturing the spectral evolution at epochs where centimeter-band emission is often still optically thick or yet to peak. However, the practical scientific yield depends on instrument-specific thresholds, the observing cadence, and the distinct temporal contributions from isotropic ejecta versus beamed relativistic jets. With the upcoming Xue-shan-mu-chang 15-meter SubMillimeter Telescope (XSMT), facility-specific forecasts are needed to test for sustained engine energy injection, as expected for a long-lived magnetar remnant rather than a promptly formed black hole. We present a unified numerical framework that couples engine-driven ejecta dynamics to non-thermal synchrotron emission, accounting for synchrotron self-absorption and deep-Newtonian effects. Adopting fixed 5$σ$ (1 h) point-source thresholds of 1.5/2.9/10.2 mJy at 230/345/460 GHz, we construct parameter-space detectability maps and estimate event rates based on current BNS merger-rate priors. For a fiducial local event at 40 Mpc, we find that a magnetar-boosted ejecta afterglow peaks on timescales of weeks to months and remains detectable long enough to allow delayed follow-up, with an expected all-sky rate of $\dot N_{\rm ej} \approx 0.05$--1.7 yr$^{-1}$ at 230 GHz for $f_{\rm mag}=1$; this rate is an upper limit and scales linearly with the long-lived magnetar fraction. Conversely, while relativistic jets produce intense early-time signals, their detection is constrained by narrow beaming and fleeting visibility. Our framework provides a quantitative basis for prioritizing gravitational-wave triggers and maximizing the scientific yield of XSMT in the multi-messenger era.

astro-ph.HE↗

arXiv2026

Hyperdeterminant wavefunctions

We systematically introduce hyperdeterminant wavefunctions as a variational-wavefunction-based theoretical framework for strongly correlated quantum states of matter, together with practical numerical simulation algorithms. This framework generalizes previously known fermionic parton constructions, yields reliable microscopics with intuitive physical pictures, and allows direct access to the fractionalized degrees of freedom together with associated microscopic effective field theories. We demonstrate the applications of this framework to fractional Chern insulators and quantum spin liquids. We comment that the hyperdeterminant states belong to a more general class of variational wavefunctions: the fused Gaussian states.

cond-mat.str-el↗

arXiv2026

Cross-validation of six dispersion measure estimation methods for FRB 20240114A

Fast Radio Bursts (FRBs) are important cosmological probes, but their applications depend critically on accurate dispersion measure (DM) determinations. We present a systematic comparison of six DM estimation methods using 2,874 bursts from FRB20240114A, the most active repeating FRB currently known, observed by FAST during a single 4.4-hr session on 2024 March 12. This large, homogeneous sample over a short timescale, during which the propagation environment is expected to be nearly static, provides an ideal benchmark for isolating algorithmic effects on DM determination. We investigate the dependence of inter-method consistency on signal-to-noise ratio (S/N), burst morphology, and radio frequency interference (RFI). Low-S/N bursts exhibit significantly larger inter-method deviations, while single-component bursts produce highly consistent DM values across methods. In contrast, complex double- and multiple-component bursts with drifting substructures lead to substantial inter-method scattering, indicating that DM discrepancies are primarily driven by algorithmic responses to burst morphology. RFI does not significantly alter the global statistical behavior of DM deviations, but it affects density-filtering methods through morphology distortion caused by frequency-channel masking. Even after imposing strict inter-method consistency constraints, FRB20240114A still exhibits notable apparent DM fluctuations spanning $\sim$528-534~pc~cm$^{-3}$ over 15,780s. For morphologically simple bursts these variations far exceed the measurement uncertainty and, on second-to-minute timescales, cannot arise from any plausible change in the line-of-sight electron column, pointing instead to a frequency-dependent emission-time structure intrinsic to the bursts that mimics dispersion.

astro-ph.HE↗

arXiv2026

Electrically Programmable Correlated Topology and Magnetism in a Moiré Trilayer

Strong electron-electron interactions underlie a wide range of quantum many-body phenomena, including magnetism, superconductivity, and charge fractionalization. A central goal is to achieve in situ control over lattice geometry, bandwidth, and band topology within a single platform. Here we realize such an electrically programmable quantum many-body system in an alternating twisted trilayer MoTe$_2$, where an out-of-plane displacement field continuously modifies the layer polarization, effective lattice, and topology of the moiré bands. At zero displacement field, the system realizes a triangular lattice hosting a correlated insulator at one hole per moiré unit cell ($ν= -1$). Doping this state produces strongly asymmetric magnetic responses: double-exchange-like ferromagnetism for $|ν| > 1$, and signatures of spin polarons and antiferromagnetism for $|ν| < 1$. At large displacement field, interlayer hybridization reconstructs the electronic structure into a honeycomb lattice with a flat Chern band, supporting integer and fractional Chern insulators. Magneto-optical measurements further reveal the signatures of gap closure and Landau-level formation from a spin-polarized Fermi surface near the crossover between the two regimes. These results establish a unified, electrically tunable platform in which correlated magnetism and topological states emerge from a single controllable band structure.

cond-mat.mes-hall↗

arXiv2026

Charge-Conjugation Violation and Population Asymmetry in Bipartite Fermionic Lattices

Charge conjugation violation (CCV) is a central concept in particle physics and appears also for quasiparticles in quantum many-body systems, which typically relies on an embedded external symmetry breaking to the underlying system. An open question is how an intrinsic CCV mechanism could emerge and what its macroscopic consequences would be. We establish sublattice kinks in bipartite fermionic lattices as a concrete setup showing intrinsic CCV. The intrinsic CCV of the sublattice kink is based on the graph-topological nature of the underlying Hamiltonian, with no explicit symmetry breaking taking place. It leads to a population asymmetry of different configurations and imprints a hidden leaf-like structure in the eigenenergy spectrum. The population asymmetry also leads to an imbalanced sublattice-kink production triggered by the vacuum-instability in the quench dynamics. Our work demonstrates the graph topology as the microscopic origin of intrinsic CCV, with the population asymmetry as the macroscopic consequence, of which the proposed setup is highly amenable to experimental implementation via cold-atom quantum simulators.

cond-mat.quant-gas↗

arXiv2026

GRB 250424A: A Case Study of Energy Injection with Multiwavelength Observations

We present a comprehensive multiwavelength analysis of the long-duration gamma-ray burst (GRB) 250424A. Our dataset spans from the prompt gamma-ray emission to late-time optical monitoring, including spectra obtained with the Keck 10\,m telescope. We find that the afterglow light curves display a prominent, simultaneous shallow decay phase in both X-ray and optical bands, followed by an achromatic transition to a standard decay regime. The broadband spectral energy distributions are well-modeled by a single power-law function, indicating a common synchrotron origin for the emission across frequencies. We interpret the afterglow evolution within the framework of a relativistic forward shock refreshed by continuous energy injection. This scenario successfully reproduces the observed temporal and spectral behavior, yielding an isotropic equivalent kinetic energy of $E_{\rm K,iso} \approx 5.5 \times 10^{52}$ erg and an injection index of $q\approx 0.34$ in a constant-density circumburst environment. The shallow decay phase is consistent with sustained energy injection lasting $\sim$ 9 ks. Despite the relatively low redshift, late-time optical observations reveal no distinct supernova component; however, our derived upper limits do not strictly rule out the presence of a typical GRB-associated supernova.

astro-ph.HE↗

arXiv2026

Switching Chern number by sliding and gating in alternately twisted tetralayer MoTe2

Switching the bulk Chern number in topological materials is of central importance for the design of topological electronic devices. Motivated by recent observations of integer and fractional quantum anomalous Hall effects in twisted transition metal dichalcogenides (tTMDs), we realize the switching of valley Chern number through sliding and gating in alternately twisted tetralayer (ATT) MoTe$_{2}$. Using large-scale density functional theory (DFT) calculations, we show that the Chern number of the first $K$-valley moiré band evolves from $+1$ to $-1$ under the interlayer sliding. Furthermore, an applied electric field can switch the valley Chern number from $-1$ to $+1$. Based on the developed continuum model, we reveal that these switching behaviors are caused by the sliding- and gate-dependent intralayer moiré potential distributions across the layers. Our results establish ATT MoTe$_{2}$ as a promising platform for engineering moiré band topologies through the design of moiré potentials with sliding in multilayer moiré systems.

cond-mat.mtrl-sci↗

arXiv2026

Atomic-Scale Observation of Symmetry Breaking in Altermagnetic MnTe

The recent discovery of altermagnetism has sparked growing interest in compensated magnetic systems as promising platforms for highly scalable spintronics. Altermagnetism is a distinct magnetic order where opposite spin sublattices are connected by rotation, yielding zero net magnetization but momentum-dependent spin splitting. To date, experimental verification of altermagnetic order has been achieved predominantly through bulk-sensitive techniques, including spin-dependent electronic spectra and transport responses. However, direct atomic-scale evidence that explicitly correlates crystal symmetry, local structural distortions, and magnetic ordering has remained unexplored. Here, we report the direct atomic-scale observation of coexisting polar distortions and altermagnetic order in MnTe, combining atomic resolution scanning transmission electron microscopy (STEM) imaging with electron magnetic chiral dichroism (EMCD) measurements. We reveal that MnTe is not an ideal uniform P63/mmc g-wave altermagnet at the atomic scale. Instead, it hosts ubiquitous inversion-symmetry-breaking distortions that lower the spin-space-group (SSG) symmetry, admits d-wave altermagnetic components, and in lower-symmetry regimes, even allow s-wave spin splitting (net magnetization). The coexistence of ferroelectric signatures and altermagnetic order establishes local lattice symmetry in MnTe as a control knob for altermagnetic spin splitting, spin current generation, and multiferroic memory applications.

cond-mat.mtrl-sci↗

arXiv2026

Ward identities and orbital magnetization in current density functional theory

We revisit the derivation of the orbital magnetization formula for periodic crystals in current density functional theory (CDFT)[1]. Our new derivation computes the linear response of the energy density to a periodic magnetic field in the long-wavelength limit. We unveil a Ward identity which connects the current vertex to the derivative of the Kohn-Sham self-energy. The result of Ref.[1] is confirmed: the orbital magnetization of the interacting solid can be computed exactly (in principle) from the self-consistent eigenfunctions and eigenvalues of the Kohn-Sham equation of CDFT.

cond-mat.mtrl-sci↗

arXiv2026

Orbital Magnetization of Correlated States in Twisted Bilayer Transition Metal Dichalcogenides

Recent observations of quantum anomalous Hall effects in moiré systems have revealed the emergence of interaction-driven ferromagnetism with significant orbital contributions. To capture this physics, we extend the modern theory of orbital magnetization to Hartree-Fock states and show that the standard expression remains valid with Hartree-Fock orbitals and Hamiltonians. We then benchmark our theory against the Kane-Mele-Hubbard model in a weak field, which yields excellent agreement with direct numerical calculations. Applying our theory to twisted MoTe$_2$ bilayers, we find orbital magnetization of order one Bohr magneton per moiré cell with a non-monotonic twist-angle dependence. Our work establishes a general theory of orbital magnetization in interacting moiré systems and provides quantitative guidance for interpreting recent experiments.

cond-mat.mes-hall↗

arXiv2026

Nonadiabatic Theory of Phonon Magnetic Moments in Insulators and Metals

We develop a nonadiabatic theory of phonon magnetic moments applicable to both insulators and metals. By relating the phonon magnetic moment to the force-velocity response of ions in a magnetic field, we derive a gauge-invariant expression using a gauge-covariant Wigner expansion. The formalism naturally separates Fermi-sea and Fermi-surface contributions and captures the full dependence on phonon frequency. In gapped systems, our theory reduces to previous adiabatic expressions in the low-frequency limit. Beyond this limit, it reveals additional contributions arising from resonant interband processes and the Fermi surface. Applying our theory to Pb$_{1-x}$Sn$_x$Te, we find that the Fermi-surface contribution substantially enhances the phonon magnetic moment, reproducing the same order of magnitude as the experimental observation. Our results provide a unified framework for describing phonon magnetic moments beyond the adiabatic regime.

cond-mat.mes-hall↗

arXiv2026

Quantum Geometric Quadrupole of Cooper Pairs

The size of Cooper pairs defines a fundamental length scale of superconductivity, conventionally set by band dispersion and the superconducting gap. This picture breaks down in flat bands, where quenched dispersion makes quantum geometry essential. Here we develop a general framework based on the Cooper pair quadrupole moment, whose trace gives the pair size. The framework holds for both dispersive and flat-band cases, and provides a unified description of the geometric origin of this length scale. In particular, when time-reversal symmetry is broken, Berry curvature enters through the phase structure of the pair wavefunction and gives an essential contribution absent from previous quantum-metric theories. Together, Berry curvature and quantum metric impose a geometric lower bound on the pair size. Applying this framework to rhombohedral graphene, we find that the Berry-curvature-induced contribution can dominate and yields pair sizes comparable to experimentally inferred coherence lengths. These results identify Berry curvature as a central geometric ingredient controlling the microscopic length scale of superconductivity.

cond-mat.supr-con↗

arXiv2026

Rotation Measure Substructures Induced by the Ponderomotive Force of Inertial \alfven Waves

The rotation measure (RM) and dispersion measure (DM) of fast radio bursts (FRBs) serve as critical probes of the magneto-ionic environments along the line of sight. The significant temporal evolution of RM observed in some repeating FRBs is generally attributed to the local environment of the source, since the intergalactic medium is not expected to vary on such short timescales. Recent observations of repeating FRB 20201124A and FRB 20220529 exhibit complex RM phenomenology, including large-amplitude global fluctuations and short-term substructures. Here, we attribute these short-term RM variations to the ponderomotive force exerted by inertial \alfven~waves (IAWs). We propose that IAWs, generated via magnetic reconnection or turbulent cascades in a low-$β$ plasma, induce nonlinear density perturbations in the source environment. We demonstrate that the resulting plasma density redistribution can produce RM suppression consistent with observed substructures. This model presents a physically motivated mechanism for the short-term RM variability observed in active repeaters. It demonstrates that such fluctuations can arise from wave-driven density cavitation within a broad, coupled parameter space involving wave amplitude, plasma density, and temperature, thereby characterizing the localized plasma dynamics required to produce the observed RM jitters.

astro-ph.HE↗