We investigate nonequilibrium dynamics and weak ergodicity breaking in a harmonically trapped spin-$3/2$ Fermi gas by using the time-dependent Hartree-Fock equation. The Shannon entropy remains bounded and oscillatory throughout the evolution, indicating restricted and nonuniform exploration of Hilbert space rather than immediate thermalization. The fidelity exhibits pronounced, nearly periodic revivals whose period is largely insensitive to particle number and interaction strength, while the revival amplitude gradually decreases with increasing system size and interaction strength. The Fourier spectrum of the fidelity reveals a set of sharp and approximately equally spaced peaks. By projecting the time-evolved state onto the instantaneous eigenbasis of the self-consistent mean-field Hamiltonian, we identify a sparse and spectrally stable manifold that forms a quasiregular energy ladder, with spacing comparable to the dominant quasienergy interval extracted from the fidelity spectrum. These results indicate that the long-lived coherent oscillations originate from collective phase interference associated with a quasiregular spectral structure embedded in the many-body continuum, rather than from a conventional eigenstate-dominated scar mechanism.

Gallium is a prototypical liquid metal and has gained renewed attention because of its unique properties. Characterizing and elucidating its atomic dynamics remains elusive despite numerous studies, primarily because of the challenges in quantifying atomic-scale dynamics in liquids. Recent developments in inelastic neutron scattering enable us to measure the Van Hove correlation function that describes the real-space motion of liquid atoms. In this work, we use this approach to reveal the dynamics in gallium liquids and find the co-existence of two dynamical medium-range orders (MROs), which have a dynamical behavior distinct from that of the short-range order (SRO). We propose that these MROs are driven by global forces in the form of two density waves, as a direct consequence of the underlying competition between ionic core repulsion and valence electron cohesion. We suggest that the density wave approach is not only applicable to other metallic liquids exhibiting similar structural anomalies, but also offers a promising direction for elucidating the dynamics of complex liquids and glasses by linking electronic-state fluctuations to atomic dynamics.

The star lattice, which can be visualized as a honeycomb network with each vertex replaced by a triangle, provides a rare platform for realizing exotic quantum states such as quantum spin liquids and disorder-driven random-singlet (RS) states. Herein, we investigate the ground-state properties of the three-dimensional (3D) stuffed hyper-star lattice ${\mathrm{Li}}_2{\mathrm{Cu}}_2$(${\mathrm{MoO}}_4{)}_3$, which exhibits a crossover from short-range spin correlations to a disorder-driven RS-like state below $T^{*}\sim 15.8\mathrm{K}$. Thermodynamic and microscopic measurements capture this crossover through a change in the power-law behavior of various observables, from $\sim T^{0.25}$ for $T>T^{*}$ to $\sim T^{-0.50}$ for $T<T^{*}$. Upon further cooling, a quasifrozen state emerges near $T_f=0.32\mathrm{K}$, likely associated with weakly coupled spin chains within the hyper-star spin network. Our results underscore the crucial role of orphan spins and weak residual interactions in stabilizing a disorder-driven quantum-disordered state in three dimensions.

We study interaction-driven quantum phases in a two-dimensional generalized Su-Schrieffer-Heeger (SSH) model defined on a square lattice with inequivalent nearest-neighbor hopping, next-nearest-neighbor hopping, and a staggered on-site potential. In the noninteracting limit, the model hosts either quadratic band touching (QBT) at the Brillouin-zone center or symmetry-protected Dirac nodes, depending on the microscopic parameters. In the parameter regime with QBT, our self-consistent Hartree-Fock analysis shows that weak to intermediate interactions can spontaneously break time-reversal symmetry and stabilize a quantum anomalous Hall (QAH) insulating phase with a finite Chern number. Interestingly, this QAH phase is found to weakly break lattice symmetries, leading to a small but finite nematic bond order. This is in contrast to the standard QAH phase in the checkerboard lattice, which preserves all lattice symmetries. Additionally, we find an enhanced bond-nematic Dirac semimetallic (BNDS) phase due to asymmetric hopping; this phase, previously identified using more advanced numerical approaches, also emerges naturally within an unrestricted Hartree-Fock framework when the bond order sector is analyzed explicitly. In the parameter regimes where QBT splits into two Dirac nodes, the QAH phase survives up to a finite staggered on-site potential. However, as the staggered potential increases, the QAH phase is suppressed while the BNDS phase grows stronger.

(2+1)-dimensional [(2+1)D] topological orders possess emergent ordinary symmetries given by a group ${\text{Aut}}_{br}\left(\mathcal{C}\right)$, which consists of the braided tensor autoequivalences of the modular tensor category $\mathcal{C}$ that describes the anyons. In this paper we discuss cases where ${\text{Aut}}_{br}\left(\mathcal{C}\right)$ has elements that neither permute anyons nor are associated to any symmetry fractionalization but still acts faithfully on the theory, which we refer to as soft symmetries. We point out that one can construct topological defects corresponding to such exotic symmetry actions by decorating with a certain class of gauged symmetry protected topological states that cannot be distinguished by their torus partition function. This gives a physical interpretation to work by Davydov on soft braided tensor autoequivalences. This has a number of important implications for the classification of gapped boundaries, noninvertible spontaneous symmetry breaking, and the general classification of symmetry-enriched topological phases of matter. We also demonstrate analogous phenomena in higher dimensions, such as $(3+1)\mathrm{D}$ gauge theory with gauge group given by the quaternion group $Q_8$.

Quad-helicoid surface states (QHSSs) are unique surface states with two pairs of helicoid surface states in topological semimetals such as Dirac semimetals. So far, topologically protected QHSSs are shown to appear in spinless systems with two $\mathcal{GT}$ symmetries and $\mathcal{T}$ symmetry ($\mathcal{G}$: glide, $\mathcal{T}$: time-reversal). In this paper, we show that topologically protected QHSSs also appear in spinful/spinless systems with only two $\mathcal{GT}$ symmetries by defining new topological charges and establishing the bulk-surface correspondence. We first define a local $Z_2\times Z_2$ monopole charge for gapless nodes at $\mathcal{GT}$-invariant high-symmetry points and a global $Z_2$ charge reflecting the global topological feature of $\mathcal{GT}$-symmetric topological semimetals. Next, we show that the latter $Z_2$ classification corresponds to the presence or absence of QHSSs on the surface with two $\mathcal{GT}$ symmetries. In addition, we provide simplified formulas of the $Z_2$ charge under additional symmetries, and clarify some symmetry conditions where QHSSs are filling enforced.

Motivated by the recent discovery of metallic surface states in the $d$-electron Kondo insulator candidates FeSi and ${\mathrm{FeSb}}_2$, along with some recent reports of magnetic correlations in the surface transport properties of FeSi, we have investigated the low-temperature surface magnetotransport properties of ${\mathrm{FeSb}}_2$. By using a Corbino disk transport geometry, we were able to isolate the electrical transport properties of a single surface of our samples and study the [110] and [101] naturally forming faces separately. Studying the relationship between the applied magnetic field, current direction, and crystal symmetry has allowed us to separate possible contributions to the magnetotransport anisotropy. Unlike previous studies of ${\mathrm{SmB}}_6$ surface states, we find no two-dimensional Drude-like dependence on field orientation relative to current direction, but instead a magnetocrystalline anisotropy that appears to originate from local moment scattering with a well-defined easy axis along the [100] direction. We compare these results with the magnetotransport properties of the conducting surface states on the [111] facet of FeSi. We also find evidence of three-dimensional variable-range-hopping conduction below the bulk-to-surface crossover, extending below 1 K, which implies that the electrical transport at the surface of these materials is carried by a thin but three-dimensional conducting channel, which is inconsistent with the lower dimensional states expected for a strong topological insulator.

${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$, a nickelate compound with a reported superconducting transition temperature of $80\mathrm{K}$, has attracted significant attention in recent years. Density-wave phenomena arising from strong electron correlations are widely regarded as key to unraveling the superconductivity mechanism, but the ordering and stability of these density waves remain a subject of contention in existing theoretical studies. In this work, we employ the variational Monte Carlo (VMC) method to thoroughly examine the nature of density waves as functions of Coulomb repulsion and exchange interactions in bilayer two-orbital models proposed for the high pressure phase of ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$. We analyze the spin and charge correlation functions in a wide range of parameter space, and delineate a schematic phase diagram that separates different density-wave ground states. Our results provide useful insights into the understanding of electron correlations in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$, and highlight the potential of VMC to elucidate its superconducting mechanism.

Due to the large number of possible defect sites characterized by different local chemical environments, investigating point defects in semiconductor alloys has been a long-standing challenge for first-principles defect calculations. In practice, it is often assumed that focusing on the energetically most favorable defect site is sufficient to provide a reliable estimation of the defect properties. Here, using a prototypical defect $\left({\mathrm{C}}_{\mathrm{N}}\right)$ in the ${\mathrm{Al}}_{0.5}{\mathrm{Ga}}_{0.5}\mathrm{N}$ alloy as an example, we show that the site occupation is highly important and critically impacts the defect-assisted nonradiative capture coefficients. We find a positive correlation between the hole capture coefficient $\left(C_p\right)$ and defect formation energy, which brings in a strong temperature dependence: the statistically averaged effective $C_p$ increases substantially with increasing the material growth temperature. Quantitative analysis demonstrates that the effective $C_p$ with equilibrium site occupations at the typical growth temperature is one order of magnitude higher than that with only the lowest-energy site considered. Further, we show that even though the lowest-energy configuration of ${\mathrm{C}}_{\mathrm{N}}$ in the alloy has the same first-nearest-neighbor environment as the one in GaN, $C_p$ in the two cases differs by more than an order of magnitude. The large difference of $C_p$ is primarily attributed to reduced electron-phonon coupling caused by lattice distortions in the alloy, which highlights the importance of lattice distortion in semiconductor alloys in addition to local chemistry. Our study provides essential insights for defect engineering in semiconductor alloys toward enhanced electronic and optoelectronic performance.

Directional scattering enabled by multimode interference in high-index nanostructures provides exceptional control over light manipulation, but achieving flexible spectral tuning remains challenging. To address this, we propose a hybrid nanoantenna that integrates transition metal dichalcogenides (TMDs) with the phase-change material ${\mathrm{Ge}}_2{\mathrm{Sb}}_2{\mathrm{Se}}_4{\mathrm{Te}}_1$ (GSST), enabling continuous spectral tuning of unidirectional forward scattering. This tunability arises from the GSST phase transition. With carefully optimized parameters, this transition induces virtually synchronous redshifts of the electric and magnetic dipole Mie resonances while preserving their near-zero phase difference, thereby maintaining the Kerker condition throughout the amorphous-crystalline transformation. This enables on-demand active spectral tuning of the unidirectional forward scattering. We further demonstrate flexible switching between single- and dual-wavelength unidirectional forward scattering enabled by the self-hybridized exciton-Mie interaction in the ${\mathrm{MoTe}}_2$-GSST nanoantenna. Additionally, we explore the influence of the GSST phase transition on the scattering directionality under self-hybridization, showing that the transition alters the overlap between the exciton and Mie resonances and thereby modulates the coupling strength, ultimately suppressing dual-wavelength scattering. Our work introduces a paradigm for actively tunable nanoantennas, combining dynamic phase-change materials with exciton resonances.

On-chip optical superchiral fields are usually generated using nanostructures. Here we demonstrate superchiral field generation using surface waves in a one-dimensional photonic crystal (PhC). The PhC supports nodal rings featuring a bandwidth-enhanced, all-angle degenerate dispersion for transverse magnetic (TM) and transverse electric (TE) surface modes. This unique degeneracy is harnessed to create simultaneous electric field and magnetic field skyrmion bags, resulting in a moiré superchiral field superlattice on the flat crystal surface. We show that the distribution of the superchirality can be modulated by the moiré angle and orbital angular momentum of the excitation scheme and the handedness of chirality is determined by the phase difference between TM and TE waves. This work proposes a simple platform for on-chip chiral sensing using tailored superchiral fields.

Simplicity in chemical composition does not always translate into simplicity in the structures and dynamics of liquids and solids. Some elementary liquid metals, such as gallium, show unusual behaviors in thermodynamic and transport properties as a result of their complex atomic structure and dynamics. In this work, we study the real-space atomic correlation function of liquid gallium by neutron scattering. In the pair-distribution function, there exist two kinds of medium-range order (MRO), characterized by oscillations beyond the first nearest neighbors. On the other hand, the first neighbor shell shows only one kind of bond. The two types of MRO are strongly overlapping in space and fluctuating in time. We propose that they are the basis for anomalous behavior of liquid gallium. This view challenges the current view that liquid gallium consists of fluctuating metallic and insulating domains. These findings shed light on the interpretation of similar microscopic anomalies observed in other semimetallic liquids.

We study the effect of quenched disorder on the non-Hermitian skin effect in systems that conserve a U(1) charge and its associated multipole moments. In particular, we generalize the Hatano-Nelson argument for a localization transition in disordered, nonreciprocal systems to the interacting case. When only U(1) charge is conserved, we show that there is a transition between a skin-effect phase, in which charges cluster at a boundary, and a many-body localized phase, in which charges localize at random positions. In the dynamics of entanglement, this coincides with an area-to-volume-law transition. For systems without boundaries, the skin effect becomes a delocalized phase with a unidirectional current. If dipoles or higher multipoles are conserved, we show that the non-Hermitian skin effect remains stable to arbitrary disorder. Counterintuitively, the system is therefore always delocalized under periodic boundary conditions, regardless of disorder strength.

Ferrimagnetic ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ grown on the (001) surface of paramagnetic ${\mathrm{Gd}}_3{\mathrm{Ga}}_5{\mathrm{O}}_{12}$ experiences an exchange bias field, which has been attributed to the magnetism of an interface layer between the two materials. We report here that when grown using sputtering and with lower postannealing temperatures than in previous works, the blocking temperature of the interface magnetic layer of a micron-sized film sample is lowered to about 7 K, while still displaying a strong exchange bias. This exchange bias is then found to be tunable between its two extreme values by varying the field cooling protocol. This is attributed to a slow and complex dynamics of the frustrated spins in the interface layer when the sample is warmed up close to the blocking (or melting) temperature.

It is widely believed that friction between materials could induce local melting. However, the criterion for identifying the occurrence of melting for a friction process is an unresolved issue. In this work, molecular dynamics simulations were conducted to investigate the friction induced melting process. A criterion for identifying liquid phase formation was established based on analysis of friction induced temperature rise and structural order destruction. Specifically, the formation of the liquid phase can only occur when both structural disorder and atomic kinetic energy conditions are satisfied. Under specific friction conditions, the contact region undergoes short-time local melting and exhibits a high local liquid nucleation rate. It is suggested that friction induced melting is a rapid heterogeneous process, which significantly differs from that induced solely by heating. Friction not only generates localized superheating in the contact region, but also causes destruction of structural order, thereby reducing the nucleation barriers for the formation of the liquid phase.

Eigenstate thermalization refers to the property that an energy eigenstate of a many-body system is indistinguishable from a thermal equilibrium ensemble at the same energy as far as expectation values of local observables are concerned. In systems with degeneracies, the choice of an energy eigenbasis is not unique and the fraction of basis states exhibiting eigenstate thermalization can vary. We present a simple example where this fraction vanishes in the thermodynamic limit for one basis choice, but remains nonzero for another choice. In other words, the weak eigenstate thermalization hypothesis is satisfied in the first, but violated in the second basis. We furthermore prove that degeneracies must abound whenever a system is simultaneously symmetric under spatial translations and reflection. Finally, we derive general bounds on how strongly eigenstate thermalization may depend on the choice of the basis, and we reveal some interesting implications regarding the temporal relaxation properties of such systems.

In the study of open quantum systems it is often useful to treat mixed states as pure states of a fictitious doubled system. In this work we explore the opposite approach: mapping isolated bilayer systems to open monolayer systems. Specifically, we show that arbitrary bilayer Hamiltonians possessing an antiunitary layer exchange symmetry, and subject to a constraint on the sign of interlayer couplings, can be mapped to Lindbladians on a monolayer system with some of the jump operators postselected on a fixed outcome (“monitored”). Low-energy states of the bilayer Hamiltonian then correspond to late-time states of the monolayer dynamics. Simulating the latter by quantum trajectory methods has the potential of substantially reducing the computational cost of estimating low-energy observables in the bilayer Hamiltonian by effectively halving the system size. The overhead due to sampling quantum trajectories can be controlled by a suitable importance sampling scheme. We show that, when the quantum trajectories exhibit free fermion dynamics, our approach reduces to the auxiliary field quantum Monte Carlo (AFQMC) method. This provides a physically transparent interpretation of the AFQMC sign-free criteria in terms of properties of quantum dynamics. Finally, we benchmark our approach on the 1D quantum Ashkin-Teller model.

Antiferromagnetic (AFM) materials show significant potential for spintronic applications because of their fast spin dynamics, magnetic stability, and uncompensated magnetic moments, which can be leveraged for information storage. In this study, we investigate long-range coupling between single-crystalline ${\mathrm{Fe}}_{0.4}{\mathrm{Mn}}_{0.6}$ (FeMn) layers separated by a Cu spacer in fully epitaxial 8-monolayer (ML) FeMn/Cu/6-ML FeMn/Co/Fe/Cu(001) heterostructures. We observe a periodic modulation of the induced perpendicular magnetic anisotropy as a function of Cu spacer thickness, with a period of approximately 5.5–6 ML. In contrast, control samples [8-ML FeMn/Cu/6-ML FeMn/Co/Cu(001)], designed with in-plane magnetization and interfacial coupling, show a similar modulation phase but a weaker variation in coupling strength. These findings provide clear evidence of: (1) long-range exchange coupling between spatially separated AFM FeMn layers across the Cu spacer, and (2) a periodic modulation of long-range AFM ordering in the FeMn films, driven by this interlayer coupling as a function of Cu spacer thickness, where this behavior is primarily governed by the out-of-plane uncompensated moments of the FeMn layers, stemming from their $3Q$-type noncollinear AFM spin structure. Our results emphasize the crucial role of AFM spin structure in mediating long-range magnetic interactions, offering valuable insights for designing next-generation AFM/normal-metal-based spintronic heterostructures.

The discovery of high-temperature superconductors remains a central challenge in materials science. Hydrogen-rich compounds are among the most promising candidates, as they can exhibit phonon-mediated superconductivity at elevated critical temperatures, though their stabilization typically requires extreme pressures. Here, we report the identification of ${\mathrm{YSbH}}_6$ as a promising superconductor by a multistage high-throughput screening on ternary A15-type hydrides, followed by a high-throughput computational search of the Y-Sb-H system, accelerated by ephemeral data derived potentials. The cubic $Pm\overline{3} {\mathrm{YSbH}}_6$ phase exhibits a predicted critical temperature of 118 K at 50 GPa, among the highest $T_{\mathrm{c}}$ reported to date for an A15 hydride at this pressure. Thermodynamic analysis shows that ${\mathrm{YSbH}}_6$ lies $\sim 100\mathrm{meV}/$ atom above the convex hull at 50 GPa, but only 26 meV/atom above the hull at 120 GPa, suggesting possible metastability and synthesis at similar high-pressure conditions. The phase is dynamically stable over a wide pressure range (20–120 GPa), displays kinetic stability at 50 GPa, and elastic stability at 20 and 50 GPa, key ingredients for long-lived metastable behavior at moderate pressures. These results highlight ${\mathrm{YSbH}}_6$ as a benchmark case illustrating the balance between high-$T_{\mathrm{c}}$ performance and limited thermodynamic stability in ternary hydrides, and underscore the importance of combined dynamic, thermodynamic, kinetic, and elastic stability analyses for guiding experimental synthesis of metastable superconductors.

We demonstrate an approach for the selective modulation of the $A_{1\mathrm{g}}$ and ${}^1{E}_{\mathrm{g}}$ optical phonon amplitudes in bismuth thin films. Combining polarization-sensitive excitation with controlled pump-pulse delays, this is shown to enable the targeted manipulation of the reflectivity signals associated with distinct phonon modes. Employing an electro-optic detection scheme reveals that the observed changes arise from selective amplification or suppression of specific symmetry components within the detected signal. This combined excitation and detection strategy is broadly applicable to other material systems and may facilitate pathways for ultrafast phononic information processing and nanoscale thermal management, critical for next-generation optoelectronic technologies.