Quasiperiodic mosaic systems with the quasiperiodic potential being added periodically with a fixed lattice interval have attracted significant attention due to their peculiar spectral properties with exactly known mobility edges, which separate localized from delocalized states. These mobility edges do not vanish even in the region of large quasiperiodic potential strength, although the width of the energy window of extended states decreases with the increase in potential strength and thus becomes very narrow in the limit of strong quasiperiodic disorder. In this paper, we study the dynamics of a quasiperiodic mosaic lattice and unravel its peculiar dynamical properties. By scrutinizing the expansion dynamics of wave packet and the evolution of density distribution, we unveil that the long-time density distribution displays obviously different behaviors at odd and even sites in the region of large quasiperiodic potential strength. Particularly, the timescale of dynamics exhibits an inverse relationship with the quasiperiodic potential strength. To understand these behaviors, we derive an effective Hamiltonian in the large quasiperiodic potential strength region, which is composed of decoupled Hamiltonians defined on the odd and even sites, respectively. While all eigenstates of the effective Hamiltonian defined on even sites are localized, the eigenstates of effective Hamiltonian defined on odd sites include both localized and extended eigenstates. Our results suggest that the effective Hamiltonian can describe the dynamical behaviors well in the large quasiperiodic potential strength region and provides an intuitive framework for understanding the peculiar dynamical behaviors in the quasiperiodic mosaic lattice.

The real-time dynamics of local magnetic moments exchange coupled to a metallic system of conduction electrons is subject to dissipative friction, even in the absence of spin-orbit coupling. Phenomenologically, this is usually described by a local Gilbert damping constant. Here, we use both linear response theory (LRT) and adiabatic response theory (ART) to derive the spin friction microscopically for a generic single-band tight-binding model of the electronic structure. The resulting Gilbert damping is time dependent and nonlocal. For a one-dimensional model, we compare the emergent relaxation dynamics as obtained from LRT and ART against each other and against the full solution of the microscopic equations of motion and demonstrate the importance of nonlocality, while the time dependence turns out to be irrelevant. In two dimensions and for a few magnetic moments in different geometries, it is found that the inclusion of nonlocal Gilbert damping can counterintuitively lead to longer relaxation times. Besides the distance dependence, the directional dependence of the nonlocal Gilbert damping turns out to be very important. Our results are based on an expression relating the nonlocal Gilbert damping to the nonlocal tight-binding density of states close to the Fermi energy. This is exact in the case of noninteracting electrons. Effects due to electronic correlations are studied within the random-phase approximation. For the Hubbard model at half filling and with increasing interaction strength, we find a strong enhancement of the nonlocality of spin friction.

The Ashkin-Teller model is a two-layer lattice model where spins in each layer interact ferromagnetically with strength $J$, and the spin-dipoles (product of spins) interact with neighbors with strength $\lambda .$ The model exhibits simultaneous magnetic and electric transitions along a self-dual line on the $\lambda \text{−}J$ plane with continuously varying critical exponents. In this article, we investigate the percolation of geometric clusters of spins and spin-dipoles denoted, respectively, as magnetic and electric clusters. We find that the largest cluster in both cases becomes macroscopic in size and spans the lattice when interaction exceeds a critical threshold given by the same self-dual line where magnetic and electric transitions occur. The fractal dimension of the critical spanning clusters is related to order parameter exponent ${\beta }_{m,e}$ as $D_{m,e}=d-\frac{5}{12}\frac{{\beta }_{m,e}}{\nu },$ where $d=2$ is the spatial dimension and $\nu$ is the correlation length exponent. This relation determines all other percolation exponents and their variation with respect to $\lambda .$ We show that for magnetic percolation, the binder cumulant, as a function of ${\xi }_2/L$ with ${\xi }_2$ being the second-moment correlation length, remains invariant all along the critical line and matches with that of the spin-percolation in the usual Ising model. The function also remains invariant for the electric percolation, forming a new superuniversality class of percolation transition.

Suppression of the superconducting transition temperature by magnetic adatoms is studied for a-few-atomic-layer-thick Pb films grown on a cleaved GaAs(110) surface. The normalized suppression rate $\eta$ varies greatly with the spin $S$ of the adatom. Furthermore, we find that $\eta$ is strongly enhanced by a coating with Au or Ag on the Pb film. On the basis of calculations using the Matsuura, Ichinose, and Nagaoka theory of the Kondo effect in superconductors, the results are explained by a strong negative $S$ dependence of the Kondo temperature $T_{\mathrm{K}}$ and a reduction of $T_{\mathrm{K}}$ due to the coating.

Long-range correlation characterizes the nondiffusive scattering paths of light through disordered media, playing an important role in the coherent control of multiply scattered light. Here, we report the long-range correlation of subsets of coherently interacting scattering paths, known as transmission eigenchannels. We find that the high-transmission eigenchannels exhibit a negative long-range correlation, in contrast to conventional positive long-range correlation. Moreover, when the transmission decreases, a prominent negative-to-positive transition of long-range correlation emerges for these eigenchannels. Finally, we demonstrate that this intriguing negative-to-positive transition originates from the characteristic transmission fluctuations of the eigenchannels. Our study provides valuable insights into the long-range correlation of scattered light in disordered media, constituting an important step toward advanced control of scattered light by manipulating the long-range correlation.

Accurate prediction of phonon thermal properties and fundamental understanding of the multiphonon interactions in phase transition dynamics and glassy dynamics are significant but challenging in halide perovskites. Herein, we investigate the anharmonic lattice dynamics and phase transition mechanism in crystalline halide perovskites $\mathrm{C}{\mathrm{s}}_3\mathrm{B}{\mathrm{i}}_2{\mathrm{I}}_6\mathrm{C}{\mathrm{l}}_3$ and $\mathrm{C}{\mathrm{s}}_3\mathrm{B}{\mathrm{i}}_2\mathrm{B}{\mathrm{r}}_9$ based on ab initio phonon dynamics. In calculating the phonon self-energy, both the bubble and the loop diagrams are considered by including the second-order perturbation term. Results indicate that (i) the transverse soft phonon mode in the Brillouin-zone boundary collapses dramatically on cooling due to the liquidlike dynamic disorder of the halogen atoms, and its phonon linewidths approach the damping limit at the critical phase transition point; (ii) the high-order anharmonicity induces phonon blueshift in the low-frequency region, leading to a qualitative competition between the enhanced phonon population and the reduced phonon scattering strength as $T$ increases, yielding a glassy thermal-transport behavior; and (iii) the giant overdamped four-phonon linewidths are responsible for the resonance scattering between neighbor nesting phonon branches, whereas the three-phonon scattering does not capture and describe accurately the dynamics behavior due to the critical scattering rules associated with the energy- and quasimomentum conservation. Taking into account the anharmonic phonon renormalization, which considers the nuclear quantum anharmonic effect, our calculated critical temperatures $T_{\mathrm{c}}$'s of the monoclinic-to-trigonal second-order phase transition are at 98.7 and 102 K for $\mathrm{C}{\mathrm{s}}_3\mathrm{B}{\mathrm{i}}_2\mathrm{B}{\mathrm{r}}_9$ and $\mathrm{C}{\mathrm{s}}_3\mathrm{B}{\mathrm{i}}_2{\mathrm{I}}_6\mathrm{C}{\mathrm{l}}_3$, respectively. These results are in excellent agreement with the experimental value of 95 K for $\mathrm{C}{\mathrm{s}}_3\mathrm{B}{\mathrm{i}}_2\mathrm{B}{\mathrm{r}}_9$. Involving the four-phonon scattering and the Wigner thermal-transport model, we recover well the experimental results of the lattice thermal conductivity and supply reasonable descriptions of it both in magnitude and $T$ dependence. This work demonstrates the effects of the $T$ evolutions of the phonon thermal properties induced by the multiphonon interactions on structural phase transitions and heat transport, deepening the underlying physical understanding of the phonon dynamics in disordered crystals with strong phonon anharmonicity.

It is recently discovered that the domain-wall skyrmion embedded in a Néel domain wall is a novel topological texture in the chiral magnet. Here, we study the dynamics of the domain-wall skyrmion driven by the current and waveguide spin wave, based on the numerical solution of the extended Landau-Lifshitz-Gilbert equation and the theoretical analysis of the Thiele equation. Compared to the regular skyrmions, the domain-wall skyrmion under a driving current or spin wave, respectively, shows a higher speed and a lower energy consumption, and without the skyrmion Hall motion. More importantly, applying the current and spin wave simultaneously, the domain-wall skyrmion is significantly accelerated through the nonlinear synergistic effect. Our results reveal the superiority of the domain-wall skyrmion owing to the extra degree of freedom, i.e., the domain wall coupling to the skyrmion, which is important in the application of the high-efficiency skyrmion-based spintronic devices. Further, compared to the previous single drive, the nonlinear synergistic effect inspires a paradigm for utilizing two or multiple driving modes in skyrmions and other similar systems.

Topological magnons emerge as topologically protected spin wave states at the edges of magnets. Here, we theoretically explore how these surface states can be harnessed to amplify the spin Seebeck effect (SSE) in antiferromagnets (AFMs) interfaced with normal metals (NMs). Based on a microscopic model of a kagome AFM, we demonstrate that broken mirror symmetry, combined with the Dzyaloshinskii-Moriya interaction (DMI), drives the system into a topological phase hosting spin-polarized magnons at the boundaries. Notably, linear response calculations reveal that in AFM/NM heterostructures the topological magnons exhibit strong coupling to the metal's charge carriers, resulting in a substantial enhancement of the SSE. The relative contribution of the topological magnons is found to be 4–5 times greater than that of the trivial magnon bands. Moreover, our results show that this enhancement is highly sensitive to the strength of the DMI.

Weak antilocalization (WAL), an increase in the electrical conductivity at low temperatures associated with the suppression of electron localization due to quantum interference effects, is often observed in topological materials. In this paper, we report the observation of WAL in topologically nontrivial metal ${\mathrm{PbTaSe}}_2$ at low temperatures. In the pristine sample, we identified the presence of WAL, which is attributed to the topologically protected backscattering. In order to investigate the influence of disorder to the WAL, we successively introduced controlled amounts of disorder by ${\mathrm{H}}^{+}$ irradiation. As disorder increases, the diplike magnetoresistance caused by WAL changes to a linear magnetoresistance (MR), and eventually to a quadratic MR as the electronic system becomes highly localized. This research unveils the significance of disorder in shaping the quantum transport characteristics of topological materials.

The quasi-one-dimensional superconductor ${\mathrm{V}}_2{\mathrm{Ga}}_5$, with the superconducting transition temperature $T_c\sim 3.6\mathrm{K}$, has recently been proposed to be an intermetallic topological material, although the experimental evidence for its nontrivial band topology is still lacking. Here, we report on its electrical and thermoelectric transport properties, as well as on its quantum de Haas-van Alphen (dHvA) oscillations. At low temperatures, ${\mathrm{V}}_2{\mathrm{Ga}}_5$ shows a linear-in-$B$ magnetoresistance, a scaling typically seen in many topological materials. Its thermoelectric power shows a pronounced two-peak profile, one centered around 70 K and the other one at $\sim 10$ K, while the Nernst coefficient exhibits a significant enhancement in the same temperature range. Quantum dHvA oscillations reveal a single frequency, with a nontrivial Berry phase close to $\pi$, associated with the putative topological carriers in its $\alpha$ pocket. Finally, the superconductivity is found to be linearly suppressed by physical pressure, with the upper critical field $H_{c2}$ consistent with the two-gap superconductivity in this topological superconductor candidate. Our results provide the direct experimental evidence for the existence of topological carriers in this quasi-one-dimensional superconductor.

The discovery of Mott insulators and superconductivity in twisted bilayer graphene has ignited intensive research into strong correlation effects in other stacking geometries. Bernal-stacked bilayer graphene (BBG), when subjected to a perpendicular electric field, exhibits phase transitions to a variety of broken-symmetry states. Notably, superconductivity emerges when BBG is in proximity to a heavy transition-metal dichalcogenide, highlighting the role of spin-orbit coupling (SOC). Here, we investigate the origin of Ising SOC and its role in the competition between superconductivity and spin- and valley-polarized states in BBG. Starting from strong electron-electron interactions on the BBG lattice, we derive a low-energy effective model near the valleys that incorporates both density-density and spin-spin interactions. Using self-consistent mean-field theory, we map out the BBG phase diagram. Our findings reveal that near the van Hove filling, a mixed spin- and valley-polarized phase dominates over superconductivity. Away from the van Hove filling, a spin-polarized, spin-triplet superconducting state arises, characterized by an in-plane orientation of the magnetic moment and an out-of-plane orientation of the $d$ vector. Contrary to previous proposals, we find that Ising SOC favors spin-valley order while suppressing superconductivity near the van Hove singularity. We discuss other potential proximity effects and suggest directions for future studies.

We illuminate the fundamental mechanism responsible for the transition between the non-Hermitian skin effect and defect-induced localization in the bulk. We study a Hamiltonian with nonreciprocal couplings that exhibits the skin effect (the localization of all eigenvectors at one edge) and add an on-site defect in the center. Using a two-scale asymptotic method, we characterize the long-scale growth and decay of the eigenvectors and derive a simple and intuitive effective model for the transition that occurs when the defect is sufficiently large that one of the modes is localized at the defect site, rather than at the edge of the system.

We investigate how the in-plane Zeeman field and the Hubbard interaction can jointly affect the topological states in the Kane-Mele-Hubbard model. At low Zeeman field, the projector quantum Monte Carlo (PQMC) simulations demonstrate Mott transitions between the higher-order topological insulator induced by the in-plane Zeeman field and the antiferromagnetic insulator induced by the Hubbard interaction. The interacting higher-order topological state on a finite-sized honeycomb lattice is characterized by the local density of states derived from the real-space spectral function. In the higher-order topological phase, the mirror-symmetry protected corner states exist on the diamond-shaped honeycomb lattice. In terms of spatial extent of corner states induced by the in-plane Zeeman field in the Kane-Mele and Kane-Mele-Hubbard models, we show that the effect of the Hubbard interaction is to contribute some extra in-plane Zeeman field. At the mean-field level, we characterize the bulk topology by the mirror winding number and calculate the full phase diagram of the Kane-Mele-Hubbard model under the influence of the in-plane Zeeman field. The mean-field phase diagram shows that a high in-plane Zeeman field drives the system into a spin-polarized (topologically trivial) phase. In particular, the upper limit of the Zeeman field that can induce corner states in the Kane-Mele model is found to be $h_c=1.0$. In the parameter region of PQMC simulations, the mean-field solutions qualitatively agree with the PQMC results.

Hydrodynamic second sound can be generated by heat pulses when the phonon-phonon interaction is dominantly momentum conserving, and the propagation of the temperature field becomes wavelike rather than diffusive. While the Boltzmann transport equation (BTE) has been widely applied to study phonon dynamics and thermal transport at the nanoscale, modeling the hydrodynamic transport regime remains challenging. The widely used relaxation-time approximation treats all phonon interactions as resistive without considering momentum conservation, resulting in the absence of phonon hydrodynamics. Rigorously solving BTE by inverting the full scattering matrix, however, is computationally demanding and has been only applied to model one-dimensional temperature variations. Here, we present an analytical Green's function formalism for solving the multidimensional Boltzmann transport equation using phonon properties from first-principles calculations. This formalism involves Callaway's scattering approximation with separate relaxation times for momentum-conserving and momentum-destroying scattering events. Green's function captures phonon dynamics in a wide range of temperature, spatial, and temporal scales, and successfully reproduces the transition from ballistic, hydrodynamic, to diffusive transport regimes. Our method avoids the computationally demanding inversion of large scattering matrices and shows good accuracies in predicting the temperature oscillation in ultrafast pump-probe characterizations with different geometries of thermal excitation.

Current-driven conductance switching in atomic-size contacts has been attributed to reversible and vibration-mediated atomic rearrangements. Here, we present a comprehensive statistical analysis on the switching properties of atomic gold, copper, and aluminium contacts fabricated by mechanically controllable break junctions. The comparative analysis shows that various bi- and multilevel switching patterns can exist with volatile as well as nonvolatile features, and with distinct material-dependent preferences among the three metals. In addition, we apply different current-biasing protocols to identify intrinsic and material-dependent switching properties under variable boundary conditions. To explore the stability of such memory states, we reveal the stochastic nature of the underlying switching mechanism and suggest a simple qualitative approach to estimate the creation and failure rate for such switching events. The approach is inspired by atomic-scale electromigration models accounting for the observed switching voltages and conductance jumps.

Kondo effect offers an important paradigm to understand strongly correlated many-body physics. Metal-phthalocyanines and metal-porphyrins provide versatile platforms for investigating Kondo effect benefiting from diverse ranges of central metal ions with different magnetic states. Here, we report the two-dimensional (2D) Kondo array of bimolecular self-assembly networks composed of iron-phthalocyanine (FePc) and iron-chiral-porphyrin (named as $\mathrm{Fe}c{\mathrm{F}}_{16}\mathrm{TPP}$) molecules. We have successfully realized the on-surface synthesis of hydrogen-bonds-connected FePc-$\mathrm{Fe}c{\mathrm{F}}_{16}\mathrm{TPP}$ checkerboard framework on Au(111). In this network, both FePc and $\mathrm{Fe}c{\mathrm{F}}_{16}\mathrm{TPP}$ molecules display Kondo resonance near Fermi level and exhibit $\left(d_{z^2}^2{d}_{\pi }^2\right)$ electronic configuration. First-principles calculations revealed that the intermolecular interaction play a vital role in modulating the symmetry of the network and the spin states of molecules. Furthermore, we have predicted that by substituting the outmost fluorine atoms with hydrogen atoms in $\mathrm{Fe}c{\mathrm{F}}_{16}\mathrm{TPP}$, a striped network consisting of FePc and $\mathrm{Fe}c\mathrm{TPP}$ molecules forms. The $\mathrm{F}{\mathrm{e}}^{2+}$ ions in $\mathrm{FePc}\text{−}\mathrm{Fe}c\mathrm{TPP}$ striped network exhibit $\left(d_{z^2}^1{d}_{\pi }^3\right)$ state, as determined through the first-principles calculations. Our work combines supramolecular chemistry for engineering the Kondo arrays and coordination chemistry for their manipulation.

Disorder scattering plays important roles in quantum transport as well as various Hall effects, including the second-order nonlinear Hall effect induced by Berry curvature dipole. Calculation of disorder-averaged transport properties usually requires substantial computational resources, especially for higher-order effects. Existing methods are either limited by approximation conditions or constrained by numerical stability, making it difficult to conveniently obtain average physical quantities over a wide range of disorder strength. In this work, we develop a general method for noninteracting system to obtain analytical expressions of disorder averages in finite orders of disorder strength. This method utilizes the Dyson equation to expand physical quantities expressed in terms of the Green's functions into series of disorder-averaged matrices, and the only approximation involved is the truncation of the Dyson equation. Therefore, this method not only avoids the brute force calculation of disorder samples, but also widely applies to different model systems, types of disorder, and the number of Green's functions in the expressions. We demonstrate the applicability of this general method by calculating averages of the linear conductance of a two-terminal system, the spin Hall conductance and the second-order nonlinear conductance of four-terminal Hall setups. It is found that truncation at the fourth order of disorder strength provides a reasonable accuracy and a convenient Padé treatment effectively extends its applicable range. Numerical results also confirms disorder enhancement of the second-order nonlinear Hall current in four-terminal systems. Moreover, more accurate predictions for a broader range of disorder strength can be achieved by including higher-order terms in a similar manner.

Monolayer graphene under a strong magnetic field near charge neutrality manifests the integer and fractional quantum Hall effects. Since only some of the four spin/valley flavors available to the electrons in each Landau level manifold are filled, they also exhibit spontaneous symmetry breaking in the spin/valley sector, a phenomenon known as quantum Hall ferromagnetism. In this work, we study quantum Hall ferromagnets in the higher Landau level manifolds of monolayer graphene and show that there is an even richer set of symmetry-broken phases than in the lowest Landau level manifold. Specifically, both valley polarized and valley equatorial (where the occupied Landau levels are in an equal superposition of both valleys) ferromagnets, antiferromagnets, and canted antiferromagnets are found. Several types of spin valley entangled phases are found, all of which manifest the simultaneous spontaneous symmetry breaking of both magnetic and lattice symmetries.