Motivated by recent experimental advancements in scanning optical stroboscopic confocal microscopy and spectroscopy measurements, which have facilitated exceptional energy-space-time resolution for investigating edge and bulk dynamics in fractional quantum Hall systems, we formulated a model for the pump-probe process on the edge. Starting with a ground state, we applied a tip potential near the fractional quantum Hall liquid edge, which was subsequently turned off after a defined time duration. By examining how the specific nature of the tip potential influences the evolution of the wave function and its distribution in energy spectrum, we identify that quench dynamics of the edge pulse leads to excitations that spread both along the edge and perpendicularly into the bulk. Moreover, magnetoroton excitations are predominant among the bulk excitations. These results align well with the experimental observations. Furthermore, we analyzed the effects of the tip's position, intensity, and duration on the dynamics.

As electronic devices continue to advance, accurate thermal management at the nanoscale is becoming increasingly crucial in engineering design. While the phonon Boltzmann transport equation (BTE) is commonly used for this purpose, conventional boundary conditions, such as the acoustic mismatch model (AMM) and diffuse mismatch model (DMM), fail to accurately predict nanoscale heat transport. In this work, we evaluate an interfacial boundary condition based on the scattering matrix (S-matrix) formalism within a low-variance direct simulation Monte Carlo (DSMC) solution of the BTE. The S-matrix framework resolves frequency- and polarization-dependent phonon transmission and reflection, enabling us to examine how microscopic details, including anisotropic scattering neglected by traditional models, lead to large differences in interfacial thermal resistance at ideal and disordered silicon/germanium interfaces. We further demonstrate that while S-matrix data can be used to accurately tune DMM for larger systems of known materials, DMM remains unsuitable for simulating nanoscale devices. Our predictions show good agreement with experimental measurements, and can be used for more accurate nanoscale thermal design of real-world devices.

A general symmetry-controlled mechanism is proposed for realizing dual flat bands of bound state in the continuum (BIC) and its radiative counterpart in photonic crystal slabs. By breaking the vertical mirror symmetry of a slab, interpolarization coupling between TE-like and TM-like modes is activated, while intrapolarization coupling among modes within the same polarization class is simultaneously preserved. The cooperative action of these two coupling channels gives rise to the concurrent flattening of both the BIC-hosting band and the radiative band, resulting in a dual flat-band system with strongly contrasting quality (Q) factors. An effective two-step coupling model is constructed to capture the essential physics and show that the emergence of the flat bands is governed by geometric tuning rather than accidental degeneracies. The mechanism is shown to be generic with respect to polarization and material platforms, enabling dual flat-band states in both low- and high-index systems, with substantially enhanced angular bandwidths in the latter. These findings establish a unified route for flat-band photonic engineering and provide a robust platform for angle-tolerant resonant photonic functionalities.

Defects in two-dimensional (2D) semiconductors play a decisive role in determining their electronic, optical, catalytic and quantum properties. Understanding how defect energy levels respond to variations in layer thickness is essential for achieving reproducible and scalable device performance. We report the persistence of layer-tolerant defect levels in rhenium disulfide $\left({\mathrm{ReS}}_2\right)$, where both donor- and acceptor-type charge transition levels remain nearly unchanged from monolayer to bulk in both AA and AB stacking. The associated two-level quantum system also retains its character across thicknesses, enabling ${\mathrm{ReS}}_2$ to serve as a platform for layer-tolerant single-photon emitters. The invariance arises from the interplay between electronic energy minimization and structural relaxation, which together counteract quantum confinement and reduced dielectric screening. Additionally, the intrinsically weak interlayer coupling in ${\mathrm{ReS}}_2$ plays a crucial role. Our findings uncover the microscopic origin of this unique behavior, distinguishing ${\mathrm{ReS}}_2$ from other transition-metal dichalcogenides and highlighting its potential for thickness-independent optoelectronic and quantum photonic applications.

A recent STM experiment in two-dimensional bilayer graphene [Y.-C. Tsui et al., Nature (London) 628, 287 (2024)], under a strong perpendicular magnetic field, has made a direct observation of the existence of three distinct filling-factor-dependent quantum phases in the lowest Landau level: the incompressible fractional quantum Hall liquid, a crystalline compressible hexagonal Wigner crystal with long-range order and rotational symmetry breaking, and a random localized solid phase with no spatial order. We argue that the spatially random localized phase at low filling is the recently proposed disorder-dominated strongly localized amorphous “Anderson solid” phase (A. Babbar et al., arXiv:2601.03521), which appears generically at a sample-dependent filling factor.

We study charge transport through a trivial-topological-trivial junction described by the continuous Qi-Wu-Zhang model, which realizes a two-dimensional Chern-insulating phase. The central region is tuned into the topological regime, while the adjoining leads remain trivial, and an electrostatic barrier of tunable height and width is applied exclusively to the topological slab. By matching wave functions across the interfaces, we obtain the angle- and energy-resolved transmission probability and demonstrate the occurrence of Klein tunneling despite the presence of a bulk spectral gap. Within the continuum Dirac description, this perfect transmission originates from the inversion of the Dirac mass across the junction, which reflects the band inversion of the central layer relative to the trivial leads. In the Qi-Wu-Zhang model considered here, this mass inversion coincides with the transition between trivial and Chern-insulating phases and is accompanied by finite Berry curvature that governs the nonlinear transport response. The resulting transmission function is then incorporated into a Landauer-Büttiker framework to analyze both linear and nonlinear transport. Closed-form expressions for the linear and nonlinear conductances are derived at zero and finite temperatures. In addition, we investigate the role of dephasing, showing how partial loss of coherence suppresses Fabry-Pérot oscillations while leaving the overall transport trends intact. Finally, we map out the interplay between barrier height, slab thickness, and topological mass parameter, identifying optimal regimes that yield enhanced rectification in the nonlinear response.

We investigate polaron dynamics in anharmonic one-dimensional crystal lattices under external electric fields, uncovering a transition from conventional polaron transport to the emergence of supersonic solectrons: electron and lattice soliton composite quasiparticles. Using a mixed quantum-classical approach that combines quantum electron evolution with classical anharmonic lattice dynamics, hence nonlinear elasticity, described by a Morse potential, we identify three distinct electric field driven transport regimes: (i) Under weak fields, subsonic polarons in anharmonic lattices accelerate continuously into stable supersonic solectrons, unlike in harmonic systems where polarons remain subsonic. (ii) At intermediate fields, Bloch oscillations generate supersonic polarons at Brillouin zone boundaries, which further accelerate in anharmonic lattices but decelerate asymptotically toward the sound speed in harmonic systems. (iii) In moderately high fields, polarons nucleated at Brillouin zone centers accelerate supersonically only in anharmonic lattices, while harmonic polarons stay subsonic. Solectrons exhibit exceptional stability against scattering, maintaining coherent propagation where conventional polarons dissociate. The formation dynamics, governed by electron-phonon coupling strength, initial wave-packet width, and field intensity, reveal optimal parameter ranges for stable high-velocity transport. This provides transformative design principles for enhancing charge carrier mobility in organic electronic materials through intentional exploitation of anharmonicity.

Deviations from diffusive heat transport in high thermal conductivity crystalline insulators are generally understood within the framework of the phonon Boltzmann Transport Equation. However, for low thermal conductivity materials with large primitive cells or strong anharmonicity, the recently developed Wigner Transport Equation is more appropriate as it includes tunneling between overlapping phonon bands. In this work, via solutions to the Wigner Transport Equation, we develop a scheme to obtain the dynamics of the phonon populations and coherences as a function of an arbitrary heat source. The approach is applied to predict size effects and dynamical thermal conductivities in ${\mathrm{CsPbBr}}_3$ and ${\mathrm{La}}_2{\mathrm{Zr}}_2{\mathrm{O}}_7$ using first-principles data as input. We predict significant deviations from the bulk thermal conductivity in these materials at length scales on the order of hundreds of nanometers to a few microns at room temperature, well within the reach of direct observation using current experimental techniques.

Distinct symmetry enriched topological orders often do not have classical distinctions. Motivated by the recent progress on the pyrochlore spin ice materials based on the dipole-octupole doublets, we argue that the dipolar spin liquid and the octupolar spin liquid can be distinguished through the magnetic charges of the magnetic monopoles in the classical spin ice regime. It is observed and predicted that the long-range dipole-dipole interaction renders the magnetic monopole of the dipolar spin ice a finite magnetic charge via the dumbbell picture even in the classical regime. For the octupolar spin ice, however, a zero magnetic charge is expected from this mechanism in the classical regime. We expect this smoking-gun observation to resolve the debate on the nature of ${\mathrm{Ce}}_2{\mathrm{Sn}}_2{\mathrm{O}}_7$, and more broadly, this work may inspire further experiments and thoughts on the Ce-pyrochlore spin liquids, Nd-pyrochlore antiferromagnets, Er-based spinels, and the distinct properties of the emergent quasiparticles in various symmetry enriched topological phases.

For strongly quantum-degenerate systems at finite temperatures, the fermion sign problem remains the major obstacle to first-principles simulations. In this work, we apply the recently proposed pseudofermion method—designed to overcome the sign problem—to strongly quantum-degenerate uniform electron gases. We find that the pseudofermion method can efficiently and highly accurately infer the energy of the uniform electron gas, while being free from the fermion sign problem. For example, in the strongly quantum-degenerate regime where restricted path-integral Monte Carlo (RPIMC) fails (33 spin-polarized electrons at the density parameter $r_s=0.5$), the relative deviation between the pseudofermion method and the exact configuration PIMC (CPIMC) result is only $0.6\%$. In particular, the pseudofermion method bridges the gap where neither CPIMC nor RPIMC can accurately simulate the regime $1\le r_s\le 2$ at the reduced temperature $\theta =0.0625$. This work demonstrates that the pseudofermion method opens a different pathway for studying strongly quantum-degenerate system in a sign-problem-free manner.

Here, by applying a comprehensive approach including magnetic, transport measurements, ARPES band structure measurements, DFT calculations, and analytical theory consideration, we unveil the puzzling origin of the negative isotropic magnetoresistance in the highly anisotropic semimetals, particularly, ${\mathrm{Eu}}_2{\mathrm{Sn}}_2{\mathrm{As}}_2$ with AFM ordering of Eu atoms. The isotropic magnetoresistance developing along with the magnetization changes up to the complete spin polarization field has been reported in several experimental studies, though its theoretical explanation has been lacking. Recently, we proposed a theoretical mechanism based on the exchange energy splitting to describe the observed magnetoresistance in layered AFM compounds by exchange splitting of the electron energy levels and by confining the electron wave functions with different spin projection in the vicinity of the respective magnetic layer. In this paper we present more detailed experimental studies of the negative magnetoresistance with several samples of ${\mathrm{EuSn}}_2{\mathrm{As}}_2$ in order to test the universal character of the exchange splitting mechanism. We also substantiate the proposed theory by comparing it with magnetotransport data, with ARPES measurements of the energy band structure, and with DFT energy spectrum calculations.

Identifying and characterizing quantum phases in the presence of long-range correlations and/or spatial disorder is, generally, a challenging and relevant task. Here, we study a generalization of the Kitaev chain with variable-range pairing and different forms of site-dependence of the chemical potantial, addressing commensurate and incommensurate modulations as well as Anderson disorder. In particular, we analyze multipartite entanglement (ME) in the ground state of dirty topological wires by studying the scaling of the quantum Fisher information (QFI) with the system size. For nearest-neighbor pairing, the Heisenberg scaling of the QFI is found in one-to-one correspondence with topological phases hosting Majorana modes. For finite-range pairing, we recognize long-range phases by the superextensive scaling of the QFI and characterize complex lobe-structured phase diagrams. The present work contributes to establish QFI and ME as useful quantities to study intriguing aspects of topological systems, also with long-range pairings and interactions. More generally, our study reports the robustness of spatial multipartite entanglement against spatial inhomogeneities.

Beyond the Landau Fermi liquid paradigm, non-Fermi liquid behavior stands as the cornerstone of deciphering emergent phenomena in strongly correlated quantum systems. In one-dimensional (1D) systems, the Tomonaga-Luttinger liquid (TLL) theory predicts exotic collective excitations and spin-charge separation, yet its experimental realization within ordered electronic phases [e.g., charge density waves (CDWs)] has long remained a key challenge. Here, we report direct spectroscopic visualization of intrinsic TLL behavior in monolayer $1T-\mathrm{VS}{\mathrm{e}}_2$ grown on bilayer graphene, where spontaneously self-organized CDW domain walls (CDW-DWs) emerge as quasi-1D quantum channels embedded within the two-dimensional host. Low-temperature scanning tunneling microscopy/spectroscopy combined with density functional theory calculations reveals definitive signatures of TLL physics, a power-law suppression of the local density of states near the Fermi level with a characteristic exponent $\alpha \approx 0.65$, and spatially resolved electronic features matching quasi-one-dimensional non-Fermi-liquid behavior described by TLL theory. Remarkably, these non-Fermi liquid features persist up to 77 K (liquid nitrogen temperature), a marked advancement over typical TLL systems, reflecting an unusually high energy scale of electron correlations in the CDW-DWs. Supported by analytical modeling incorporating substrate screening effects, our analysis rules out conventional explanations (e.g., single-particle scattering, Peierls distortions) and confirms that the observed spectral gap originates from collective 1D correlation effects. These findings establish CDW-DWs in $\mathrm{VS}{\mathrm{e}}_2$ as a robust, tunable platform for realizing correlated 1D quantum states in van der Waals materials, opening avenues for exploring exotic non-Fermi liquid phases and designing low-dimensional quantum devices.

In this work, we study the temperature-dependent Seebeck coefficient and electrical conductivity of pristine and Bi-doped SnSe to clarify the microscopic origin of carrier-type reversal in lightly doped compositions. Pristine SnSe remains $p$-type over the full temperature range, while Bi substitution drives $n$-type transport. The 2% Bi-doped sample exhibits negative Seebeck coefficients at low temperature, followed by an $n$-to-$p$ polarity reversal near 550 K, consistent with bipolar transport and carrier compensation, whereas the 6% Bi-doped sample remains robustly $n$-type up to 880 K. The experimental data are analyzed using a self-consistent two-carrier transport model with a smooth interpolation across the Pnma-to-Cmcm structural transition. To connect the extracted transport trends to electronic structure evolution, we perform first-principles calculations for Bi-doped SnSe in both phases. The calculated band structures show that polarity switching at low Bi concentration arises from the temperature-driven evolution of the band edges and the Fermi level, along with a progressive narrowing of the band gap that promotes intrinsic excitation. Electron-phonon self-energy calculations further indicate a monotonic reduction of the Pnma band gap with increasing temperature, providing a direct electronic mechanism for the onset of bipolar transport prior to completion of the structural transition.

In experiments, the carrier mobility of materials is usually evaluated based on Hall effect measurements. For most semiconductors, the mobility obtained by this method (Hall mobility) is a good estimate of the drift mobility. However, in this work we find that for Dirac materials such as graphene, the ratio of Hall mobility to drift mobility, which is known as the Hall factor, cannot be simply approximated as 1, and its value varies drastically with doping concentration and temperature. We consider full electron-phonon coupling and solve the linearized Boltzmann equation (without making approximations) to derive analytical formulas for drift mobility, Hall mobility, and Hall factor of Dirac materials under arbitrary charge doping and temperature conditions. By fitting the parameters of our model through first-principles calculations, we compute the Hall factors of several common Dirac materials. The Hall factor of graphene, ${\mathrm{Be}}_3{\mathrm{C}}_2$ monolayer, ${\mathrm{VCl}}_3$ monolayer, and $\alpha$-graphyne at 300 K is determined to be 2.31, 2.76, 4.60, 1.38, respectively.

The layer-polarized anomalous Hall effect (LP-AHE), observed in topological systems and inversion-asymmetric valleytronic systems, has attracted significant interest. However, its practical application is limited by stringent requirements of either a continuously applied external electric field or the spontaneous breaking of space-inversion P symmetry within each sublayer. Here, we demonstrate a sliding-induced mechanism for achieving an intrinsic and switchable LP-AHE in van der Waals systems. We show that interlayer sliding, a natural degree of freedom in van der Waals materials, spontaneously breaks the overall P symmetry and establishes a staggered interlayer coupling based on the $\mathit{k}·\mathit{p}$ model, which directly generates a layer-polarized Berry curvature and the associated LP-AHE without any external fields. Notably, this sliding-induced LP-AHE is inherently linked to sliding ferroelectricity. The resulting internal polarization field couples strongly with both the layer and valley degrees of freedom, enabling a nonvolatile and reversible control of the Hall effect through external field-driven sliding manipulation. Beyond a general $\mathit{k}·\mathit{p}$ model analysis, we quantitatively demonstrate this effect in a realistic material, bilayer ${\mathrm{CoBr}}_2$, via first-principles calculations. Starting from an inversion-symmetric AA stacking, lateral sliding transitions the system into a ferroelectric state with a sizable and layer-polarized anomalous Hall conductivity. Our work establishes interlayer sliding as a powerful control knob for broadening the scope of LP-AHE research and opens new avenues for developing future memory and valleytronic devices.

Nonreciprocity breaks the symmetry between forward and backward propagation, giving rise to a range of peculiar wave phenomena. In this Letter, we investigate Anderson localization in higher-dimensional nonreciprocal lattices. Focusing on the two-dimensional Hatano-Nelson model, we uncover anisotropic hybrid modes (HMs) that exhibit skin localization along one direction and Anderson localization along the other. We determine the Anderson transition along different directions via the transfer matrix approach and finite-size scaling of Lyapunov exponents. This allows us to map out mobility edges that separate HMs from normal skin modes and Anderson localized modes (ALMs), revealing an ALM-HM-ALM reentrant transition. Our analysis extends to arbitrary dimensions, and we demonstrate the existence of skin-Anderson transitions on the infinite-dimensional nonreciprocal Bethe lattice using the forward-scattering approximation.

Nanosized hafnia-zirconia ${\mathrm{Hf}}_x{\mathrm{Zr}}_{1-x}{\mathrm{O}}_2$ in the form of thin films, multilayers, and heterostructures are indispensable silicon-compatible ferroelectric materials for advanced electronic memories and logic devices. The distinctive feature of nanoscale hafnia-zirconia are the critical sizes of ferroelectricity appearance, whereas the critical sizes of ferroelectricity disappearance exist in other ferroelectrics. Using the Landau-Ginzburg-Devonshire free energy functional with higher powers, trilinear and biquadratic couplings of polar, nonpolar, and antipolar order parameters, we calculated analytically the strain-dependent critical sizes of the ferroelectricity appearance and disappearance, analyzed how the size effect and mismatch strains influence the phase diagrams and polarization switching barrier in epitaxial ${\mathrm{HfO}}_2$ thin films and nano-islands with the out-of-plane spontaneous polarization. We have shown that the critical thickness/height of out-of-plane spontaneous polarization disappearance is determined by the size dependence of the depolarization field and correlation effects. The critical thickness/height of the ferroelectricity appearance is determined by the size dependence of the effective mismatch strain considering possible appearance of misfit dislocations and lateral relaxion of strains. Derived analytical expressions can be generalized for ${\mathrm{Hf}}_x{\mathrm{Zr}}_{1-x}{\mathrm{O}}_2$ solid solutions, providing that corresponding parameters of the free energy are known from the first-principles calculations.