The selective transport effect in p-n zigzag graphene ribbon junctions has so far been attributed to the parity of the energy bands. Through the analysis of the electron transmission in two-size zigzag graphene ribbons, we unveil that this parity effect depends also on the spatial arrangement of the p-n ribbon sections. We further elucidate that highly dispersive edge states can mitigate and even eliminate this effect. Our findings shed light on the parity selective transport effect in zigzag graphene ribbons and open pathways for tuning quantum transport in graphene systems.

Dynamic quantum phase transitions (DQPT) following quantum quenches exhibit singular behavior of the overlap between the initial and evolved states. Here we present a formalism to incorporate a geometric phase into quench dynamics of mixed quantum states, a process named the Uhlmann quench, based on the Uhlmann parallel transport. To overcome the incompatibility between the Uhlmann parallel-transport condition and Hamiltonian dynamics, we formulate the evolution of purification of the density matrix in a form which not only respects the dynamics according to the density matrix but also follows the Uhlmann parallel-transport condition to generate a geometric phase after a quantum quench. For cyclic processes exemplified by a spin-1/2 system, geometric DQPTs (GDQPTs) can emerge with both singular behavior in the dynamic analog of the free energy and jumps of the geometric phase. Moreover, the Uhlmann phase reflecting the holonomy is generated at the end of each cycle. The Uhlmann quench thus paves the way for investigating the interplay between quantum dynamics and geometric processes in mixed states.

This work systematically investigates the lattice dynamics and phonon thermal transport behavior of the typical negative thermal expansion (NTE) material, cubic ${\mathrm{ScF}}_3$. By incorporating thermal expansion, the discrepancy between theoretically predicted and experimentally observed lattice thermal conductivity (${\kappa }_{\mathrm{L}}$) is resolved using self-consistent phonon theory, combined with the three- and four-phonon scattering. Our findings reveal that four-phonon interactions significantly increase the ${\kappa }_{\mathrm{L}}$ of ${\mathrm{ScF}}_3$, which contradicts the traditional intuitive impression that four-phonon interactions suppress thermal transport. This counterintuitive behavior is attributed to the hardening of two rotating phonon modes induced by quartic anharmonicity, suppressing anharmonic scattering and increasing the ${\kappa }_{\mathrm{L}}$. Furthermore, we show that thermal expansion enhances anharmonic scattering in ${\mathrm{ScF}}_3$, leading to a decrease in ${\kappa }_{\mathrm{L}}$. This suppression of ${\kappa }_{\mathrm{L}}$ becomes more pronounced at high pressures due to the significantly enhanced NTE behavior; for instance, the room-temperature ${\kappa }_{\mathrm{L}}$ of ${\mathrm{ScF}}_3$ is reduced by up to 59% at 0.6 GPa. Our work provides deeper insights into the effects of four-phonon interactions and thermal expansion on thermal transport properties.

Two-dimensional coherent spectroscopy (2DCS) with terahertz radiation offers a promising new avenue for the exploration of many-body phenomena in quantum magnets. This includes the potential diagnosis of fractionalized excitations, for which linear response often struggles due to the indistinguishability of a continuum of fractional excitations from that caused by disorders or impurities. However, the interpretation of the complex results produced by 2DCS remains a challenge. Here, we explore a numerical approach based on exact diagonalization (ED) to help push forward our understanding of 2DCS and, as an example, use it to study the impact of confinement in the one-dimensional transverse field Ising (TFIM) model. We first validate our approach by comparing numerical ED and exact analytical results for the spectroscopic signatures of fractionalized spinons in the model, which exhibits a sharp spinon-echo signal in 2DCS, and show how to understand the finite-size effects inevitable with the inherently small system sizes in ED calculations. By augmenting the model with a longitudinal field, which breaks integrability and introduces confinement of spinon pairs, we observe significant changes to the 2DCS spectrum, such as nonsymmetric broadening of the spinon-echo signal. To further elucidate these changes, we introduce a “four-kink” approximation, an effective model that captures the interactions between multiple (confined) spinon pairs. Comparing ED data to these four-kink results provides understanding of the multiple features of the 2DCS spectra, allowing us to interpolate between finite-system size data and the thermodynamic limit. One advantage of our ED approach is its possible extension to finite temperatures, which we explore using thermally pure quantum states and demonstrate how the intensity and spectroscopic patterns of 2DCS change when going beyond the integrable model. Our numerically exact results provide a benchmark for future experiments and theoretical studies relying on approximation methods and pave the way for the exploration of fractionalized excitations in quantum magnets.

The quasiparticle scattering interference (QSI) is intimately related to the nature of the quasiparticle and of its interplay with a variety of electronic orders and superconductivity. Here, starting from the microscopic octet scattering model, the nature of QSI in cuprate superconductors is studied in the $T$-matrix approach. In particular, a method of the inversion of matrix is developed to accurately derive the $T$ matrix for various kinds of impurities, and then the obtained $T$ matrix is employed to calculate the local density of states (LDOS). It is shown that the overall features of the LDOS modulation can be described qualitatively by taking into account the quasiparticle scattering from a single impurity on the kinetic-energy-driven homogeneous superconducting state, where the QSI scattering wave vectors ${\mathbf{q}}_i$ and the related QSI peak dispersions are internally consistent within the octet scattering model. However, the pronounced QSI peaks in the momentum-space LDOS modulation pattern for a single impurity are smeared heavily in the case for multiple impurities, and then the momentum-space LDOS modulation for multiple impurities exhibits a speckle pattern. Moreover, the momentum-space LDOS modulation for Gaussian random distribution of on-site impurity at a relatively large deviation displays a similar behavior of the LDOS modulation for multiple impurities. The theory also indicates that the impurity weight linearly increases with the increase of the impurity scattering strength for the weak scattering strength and tends to saturate in the strong scattering strength, while it decreases with the increase of the impurity-scattering screening length for the short screening length and saturates in the long screening length.

We propose a class of general non-Hermitian quasiperiodic lattice models with exponential hoppings and analytically determine the genuine complex mobility edges by solving its dual counterpart exactly utilizing Avila's global theory. Our analytical formula unveils that the complex mobility edges usually form a loop structure in the complex energy plane, i.e, the mobility ring. By shifting the eigenenergy a constant $t$, the complex mobility edges of the family of models with different hopping parameter $t$ can be described by a unified formula, formally independent of $t$. By scanning the hopping parameter, we demonstrate the existence of a type of intriguing flagellate-like spectra in the complex energy plane, in which the localized states and extended states are well separated by the complex mobility edges. Our result provides a firm ground for understanding the complex mobility edges in non-Hermitian quasiperiodic lattices.

An integrable model perturbed by special “weak-integrability-breaking” perturbations thermalizes at timescales much longer than predicted by Fermi's golden rule. Recently, a systematic construction of such perturbations based on the so-called long-range deformations of integrable chains was formulated. These perturbations, obtained as truncations of the long-range deformations in some small parameter expansions, can be viewed as produced by unitary rotations of the short-range integrable models. For infinite systems, several “generators” (extensive local, boosted, and bilocal operators) of weak perturbations are known. The main aim of this work is to understand the appropriate generators in finite systems with periodic boundaries since simple counterparts to boosted and bilocal operators are not known in such cases. We approach this by studying the structure of the adiabatic gauge potential (AGP), a proxy for such generators in finite chains, which was originally introduced as a sensitive measure of quantum chaos. We prove an exact relation between the AGPs for the boosted and bilocal classes of generators and note that the counterpart to the boost does not appear in a closed analytic form in finite systems but shows quasilocality nonetheless. We also introduce and study strictly local variants of weak-integrability-breaking perturbations.

In recent decades, the real-space finite-difference implementations of Kohn–Sham density functional theory have exhibited substantial improvements in computational efficiency for large-scale systems. However, the substantial memory consumption arising from the numerous grid points has begun to limit the widespread adoption of this method. In this study, a general method is presented—applicable to both periodic and Dirichlet boundary conditions—to reduce the number of real-space grids. This approach introduces a truncation of the real-space grids based on atomic positions, which reduces memory requirements and enables a more efficient real-space scheme tailored for simulating low-dimensional and porous materials with uneven spatial distributions. By testing the method on zero-dimensional clusters, one-dimensional tubes, two-dimensional clusters adsorbed on graphene, and three-dimensional metal-organic framework materials, a 30–73% reduction in grid points and a 36–71% reduction in computational time per step are observed for simulations with a 2 meV/atom energy difference.

Silicon (Si) dominates the semiconductor industry but currently suffers from significant hole mobility degradation in advanced transistors due to its abnormally low hole mobility ($505{\mathrm{cm}}^2/\mathrm{Vs}$), compared to its group IV neighbors, diamond and germanium (Ge) (both $\sim 2000{\mathrm{cm}}^2/\mathrm{Vs}$). While Ge's high mobility is understandable by its lighter effective hole mass due to its narrower direct bandgap at $\mathrm{\Gamma }$ point, diamond's superior hole mobility remains difficult to understand since its bandgap is ultrawide. Conventional wisdom attributes diamond's high mobility to reduced phonon scattering due to high acoustic phonon group velocity and optical phonon frequency, overcoming its heaviest effective mass. However, our study reveals that this mechanism alone is insufficient to explain the observed mobility. We demonstrate that the diamond's abnormally light effective hole mass is a primary factor contributing to its high mobility; otherwise, its hole mobility would be approximately nine times lower than Si's. The unexpectedly light mass in diamond stems from larger transition matrix elements, resulting from substantial electronic wave-function overlap between valence and conduction bands, remarkably overcoming the effect of diamond's large bandgap. Furthermore, our investigation uncovers a unique feature in diamond's valence band structure: an inherent strain-enhanced mobility characteristic, where the top valence band manifests as a light-hole (lh) state along certain crystallographic directions (e.g., [100]), instead of the typical heavy-hole (hh) state. Contrary to prevailing assumptions, we observe a strong coupling between holes and transverse acoustic (TA) phonons, and even TA scattering dominates over longitudinal acoustic (LA) scattering in both diamond and Si, challenging the long-held belief that TA scattering is negligible. Our calculations yield a dilation deformation potential of 3.45 eV for diamond, significantly diverging from previously reported values, e.g., 7 or $-35$ eV. This discrepancy further highlights limitations in understanding individual scattering mechanisms in diamond using classical phenomenological models. These findings shed new light on the hole mobility in semiconductors and provide new clues to enhance further the hole mobility in group IV semiconductors towards advanced semiconductor technology nodes.

A $p-n$ junction, induced in graphene by gating, works to contrast the edge states of electrons and holes on each side of it. In a magnetic field those edge states carry two species of persistent current, which are intimately tied to the edge-mode spectra. We study how those persistent currents change along each side of the junction as the Fermi level is varied, with special emphasis on the electron-hole conjugation property of the Dirac electrons. A close look is made into the electromagnetic response of the valence band filled with negative-energy electrons, or the Dirac sea, which as a whole turns out to be electrically inactive while showing intrinsic orbital diamagnetism. Recently, in experiment, it became possible to observe local currents in planar samples by use of a nanoscale magnetometer. The $p-n$ junctions in graphene and related atomic layers, via detection of associated microscopic currents, will be a useful platform for exploring many-body quantum phenomena.

Manipulation of the magnetic ordering of a spin-$\frac{1}{2}$ crystal system is often a challenge as the antiferromagnetic ordering is naturally favored. In this study, by carrying out density functional theory calculations and semi-classical Monte Carlo simulations on $A$-site ordered perovskites ${\mathrm{CaCu}}_3{\mathrm{B}}_4{\mathrm{O}}_{12}$ (B = Ge, Ti, Sn), we propose that a series of magnetic phases can be stabilized in this Cu-spin-$\frac{1}{2}$ lattice. The crossover can occur from one phase to the other by changing the stoichiometry at the magnetically inactive $B$-site. Our density functional calculations infer ferromagnetic ordering for ${\mathrm{CaCu}}_3{\mathrm{Ge}}_4{\mathrm{O}}_{12}$ and ${\mathrm{CaCu}}_3{\mathrm{Sn}}_4{\mathrm{O}}_{12}$ and G-type antiferromagnetic (G-AFM) ordering for ${\mathrm{CaCu}}_3{\mathrm{Ti}}_4{\mathrm{O}}_{12}$. We observe that for both Ge and Sn doping around the doping concentration of $x=0.875$, the systems undergo a transition from G-AFM to ferromagnetic (FM) phase. Furthermore, we project pressure as a useful external tool to introduce magnetic crossovers in these stoichiometrically varying systems. The magnetic orderings are governed by nearest-, second-nearest-, and third-nearest-neighbor exchange couplings ($J_1, J_2, J_3$). In addition, we present a comprehensive magnetic phase diagram using Monte Carlo calculations based on the half-filled Hubbard model for the Cu-based $A$-site ordered perovskite systems and illustrate how the competition among exchange couplings controls the magnetism in these systems.

At filling factor $\nu =0,\pm 1$, the ground state of graphene is a particular SU(4) ferromagnet which hosts a rich phase diagram along with several spin, pseudospin, or “entanglement” magnon modes. Motivated by recent experiments, we study a $\nu =-1\left|0\right|-1$ Fabry-Pérot magnonic junction. If the ground state at $\nu =0$ is spin polarized, there exist two spin modes which interfere and create a beating pattern, while pseudospin modes are reflected. The same scenario occurs for pseudospin magnons if the $\nu =0$ ground state is spin polarized. The observation of such an interference pattern would provide information on the low-energy anisotropies and thus on the ground state.

Recently proposed $p$-wave magnets are time-reversal preserved antiferromagnets, where the detection and control of a domain wall is a highly nontrivial problem. We study a one-dimensional hybrid system made of a $p$-wave magnet and a metal possessing the orbital degree of freedom. The hybrid system is a topological insulator without the spin-orbit interaction. There emerge two boundary states per one boundary, because the system is mapped to a set of two copies of a topological insulator. Each copy resembles the long-range Su-Schrieffer-Heeger model, but their topological phase diagrams are different. A topological interface state emerges at a domain wall in the $p$-wave magnet, which is charged due to the Jackiw-Rebbi mechanism. Consequently, a domain wall in the $p$-wave magnet will be controllable and detectable purely by electrical means. We also study Majorana fermions induced by proximity coupling of $s$-wave superconductivity and a $p$-wave magnet.

We construct a multiband $\mathbf{k}·\mathbf{p}$ Hamiltonian in monolayer and bilayer double-layer honeycomb III-V compounds including spin-orbit coupling (SOC) based on the invariant theory. The Hamiltonian can describe electronic structures near the $\mathrm{\Gamma }$ point of the Brillouin zone and anisotropic spin splitting, which is in good agreement with first-principles calculations. These SOC effects contribute to the existence of current-induced spin polarization (CISP) and spin Hall effect (SHE). The interplay between Zeeman and Rashba SOC leads to Lifshitz transitions for CISP and SHE at the maximum of lower-valence bands. Our work offers a possible approach for constructing 2D III-V compounds spintronic devices.

We report an efficient numerical approach to compute the different components of the orbital Hall responses in disordered topological materials from the Berry phase theory of magnetization. The theoretical framework is based on the Chebyshev expansion of Green's functions and the off-diagonal elements of the position operator for systems under arbitrary boundary conditions. The capability of this scheme is shown by computing the orbital Hall conductivity for gapped graphene and for the Haldane model in the presence of nonperturbative disorder effects. This methodology enables realistic simulations of orbital Hall responses in highly complex models of disordered materials.

${\mathrm{Ferromagnet}}_1$/nonmagnetic metal/${\mathrm{ferromagnet}}_2$ (${\mathrm{FM}}_1/\mathrm{NM}/{\mathrm{FM}}_2$) trilayers have garnered considerable attention because of their potential in spintronic applications. A thorough investigation of the spin transport properties of these trilayers is therefore important. Asymmetric trilayers, particularly those including platinum (Pt) as a spacer, are less explored. Pt mediates exchange coupling between the two FM layers and thus offers a unique platform to investigate the spin transport properties under indirect exchange coupling conditions through the spin-pumping mechanism. We study the static and dynamic magnetic properties of a $\mathrm{N}{\mathrm{i}}_{80}\mathrm{F}{\mathrm{e}}_{20}\text{/}\mathrm{Pt}\left(t\right)\text{/}\mathrm{Co}$ trilayer system through vibrating sample magnetometry and spin pumping based on ferromagnetic resonance (FMR) spectroscopy by varying the Pt spacer thickness. Though a powerful method for characterizing the dynamic magnetic properties of FM layers, FMR is seldom the only technique used for investigating spin transport characteristics of asymmetric trilayers. Our analytical focus on the acoustic mode, facilitated by the distinct magnetizations of the ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ and Co layers, allows for the isolation of individual layer resonances. The derived spin pumping induced damping (${\alpha }_{\mathrm{sp}}$) of the ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ and Co layers reveals a direct dependence on the Pt spacer thickness. Furthermore, fitting of the weighted average of the damping parameters to the ${\alpha }_{\mathrm{sp}}$ of the acoustic mode reveals that the observed FMR spectra are indeed a result of the in-phase precession of the magnetizations in two FM layers. The extracted effective spin-mixing conductance ($g_{\mathrm{eff}}^{\uparrow \downarrow }$) varies with the FM/NM interface, specifically $1.72\times {10}^{19}{\mathrm{m}}^{-2}$ at the ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}/\mathrm{Pt}$ interface and $4.07\times {10}^{19}{\mathrm{m}}^{-2}$ at the Co/Pt interface, indicating a strong correlation with interfacial characteristics. Additionally, we deduce the spin diffusion length in Pt to be between $1.02$ and $1.55$ nm and calculate the interfacial spin transparency ($T_{\mathrm{in}}$) and spin current densities, highlighting significant disparities between the ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}/\mathrm{Pt}$ and Co/Pt interfaces. This detailed analysis enhances our understanding of the spin transport in ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}/\mathrm{Pt}/\mathrm{Co}$ trilayers. It offers insights important for advancing spintronic device design and lays the groundwork for future theoretical investigations of asymmetric trilayer systems.

We investigate topological gauge-theory terms and quantum criticality in a spin-1 Kitaev chain with general single-ion anisotropies (SIAs). The ground-state phase diagram, including the Kitaev spin liquid (KSL) and gapless dimer phases, is determined by the infinite time evolving block decimation (iTEBD) method. A quantum phase transition between the KSL and dimer phases occurs by varying uniaxial SIA, analogous to the confinement-deconfinement transition in the lattice Schwinger model with a topological $\theta$ angle of $\pi$. Introducing rhombic SIA shifts this angle from $\pi$, resulting in $y$- and $x$-ferroquadrupole phases. The transition between these phases can occur through a crossover in the KSL phase or a genuine phase transition along a deconfined line. We map the spin-1 Hamiltonian to an effective spin-1/2 PXP Hamiltonian, with uniaxial SIA corresponding to uniform detuning and rhombic SIA to staggered detuning. We explore the hierarchical fragmentation of the Hilbert space, revealing that quantum many-body scars (QMBSs) emerge under weak uniform detuning, while slow dynamics under large staggered detuning is accurately captured by a second-order effective Hamiltonian via the Schrieffer-Wolff transformation. Our work establishes a framework for simulating topological $\theta$ angles and ergodicity-breaking dynamics, bridging higher-spin generalizations of scarred models with lattice gauge theories, potentially realizable using state-of-the-art cold-atom quantum simulators.

The nonlinear dynamics of magnetization in antiferromagnets, resulting in high-frequency spin waves (high-order harmonics) as signal carriers, enable fast magnetic state switching in spintronic devices. More harmonic orders potentially allow more information to be conveyed by the spins. Developing theoretical models to describe these waves in antiferromagnets is essential for predicting their properties and guiding experimental efforts. Here we consider the role of linear and quadratic spin-phonon couplings (SPCs) in achieving high-order harmonics in the THz magnetization of a gapped antiferromagnetic spin chain. A THz steady laser's electric field indirectly drives spins via phonons. We analyze the resulting nonlinear dynamics using spin-wave theory, mean-field theory, and the Lindblad formalism. We highlight the distinct mechanisms for harmonic generation when a phonon is coupled to the easy plane and easy axis of spins. Moreover, we observe that quadratic SPC blocks odd harmonics due to invariant inversion symmetry, while linear SPC generates both odd and even harmonics. We also investigate the effects of drive frequency, drive amplitude, phonon damping, and spin damping on the number of harmonics. Our findings offer an alternative pathway for developing nonlinear magnonics.

We report here an equation-of-state measurement of ${\mathrm{Fe}}_2{\mathrm{O}}_3$ obtained with laser-driven shock compression. The data are in excellent agreement with previous dynamic and static compression measurements at low pressure, and extend the known Hugoniot up to 700 GPa. We observe a large volume drop of $\sim 10\%$ at 86 GPa, which could be associated, according to static compression observations, with the iron spin transition. Our measurements also suggest a change of the Hugoniot curve between 150 and 250 GPa. Above 250 GPa and within our error bars, we do not observe significant modifications up to the maximum pressure of 700 GPa reached in our experiment.

Substantial interest has been sparked by experimental observations of spontaneous orbital magnetism in moiré materials and multilayer graphene, with a particular focus on phenomena related to orbital magnetization (OM). Nonetheless, optical manipulation of OM remains largely unexplored. In this work, we develop a Floquet formalism for calculating OM induced by a low-intensity, adiabatically switched, circularly polarized field in extended systems. Using this formalism, we investigate the optically induced OM in twisted ${\text{MoTe}}_2$, and reveal that it can be substantially modulated through adjusting chemical potential, interlayer bias, and optical field (specifically intensity, frequency, and chirality). Remarkably, we discover a significant inverse Faraday effect that is inversely proportional to the cube of the frequency. Our findings highlight the potential of circularly polarized light to induce and manipulate magnetism in moiré materials.