The amplitude of charge-to-spin conversion, namely, the spin Hall effect (SHE), in bismuth (Bi) strongly depends on its crystal orientation. The conversion efficiency at room temperature in rhombohedral (110) bismuth is notably large, as expected from its large spin-orbit interaction, and such a large SHE is ascribed to the large effective $g$ factor in bismuth [Fukumoto et al., Proc. Nat. Acad. Sci. USA 120, e2215030120 (2023)]. Despite the successful observation of the large conversion efficiency, a more detailed physical mechanism of the SHE in (110) bismuth is still elusive and under debate. In this work, we investigate the temperature dependence of charge-to-spin conversion in an epitaxial $\mathrm{Bi}\left(110\right)/\mathrm{Ni}$ bilayer system using the second harmonic Hall method, revealing that both spin Hall conductivity and spin diffusion length augment with decreasing temperature. This finding suggests that spin scattering in (110) bismuth is dominated by the Elliott-Yafet mechanism, and the charge-to-spin conversion is mainly attributed to skew scattering.

We report an experimental study of spin-wave modes in individual cylindrical nanowires, a textbook situation of confined spin waves in three-dimensional nanomagnetism. We observe discrete modes of thermal spin waves with microfocused Brillouin light scattering, whose frequencies $f$ shift to higher values as the applied longitudinal induction magnetic field $B_z$ increases. Micromagnetic simulations allowed us to associate every $f\left(B_z\right)$ curve to a given spatial mode, labeled with radial and azimuthal indices $\ell$ and $m$.

Controlling the velocity of the acoustic wave is critical for advancing time-domain signal processing. However, current slow acoustic configurations suffer from narrowband and backscattering loss. Here, we propose broadband topologically protected slow acoustic reciprocal systems via multiwinding modulation in the Brillouin zone (BZ). By coupling the resonance-induced nearly flat bands and the topological edge states (TESs), hybridized TESs with multiple windings across the BZ are formed, which result in broadband slow acoustic waves with controllable velocity. The relative bandwidth of $\sim 7\%$ and the velocity of $0.04c_0$ ($c_0$ is the acoustic wave velocity in air) are achieved, which greatly outperforms conventional methods. Our work paves the way for the development of high-performance acoustic devices.

We investigate a many-body interacting system of quantum kicked rotors, where each rotor resides in its respective quantum resonance. Rich many-body dynamics are found to emerge from the interplay between the principal and secondary resonances. In particular, for both the wavepacket and bipartite entanglement entropy, we analytically demonstrate three distinct dynamical regimes—quadratic spreading (growth), period-2 oscillation, and their hybrid—governed by the respective symmetries of the relevant potentials. Based on these symmetries, the connection between the wavepacket and the entanglement dynamics is illustrated. Other related issues are also discussed, including higher-order resonance effects, the robustness of the predicted dynamical behaviors, extension to many-body kicked tops, and relevance to experimental studies.

Magnetoelastic coupling between surface acoustic waves (SAWs), spin waves, and magnetic textures enables tunable magnetoacoustic functionality. Synthetic antiferromagnets (SAFs) provide a suitable platform owing to their adjustable SW spectra and negligible stray fields. Here we investigate how a Bloch-type domain wall (DW) in a CoFeB/Ru/CoFeB SAF modifies SAW propagation. Analytical modeling and micromagnetic simulations show that SAWs in the nonuniform SAF decompose into three magnetoelastic eigenmodes. Near the magnetoelastic resonance, the SAW transmission across the DW displays pronounced frequency-dependent oscillations. We trace this behavior to interference among the eigenmodes, rather than the conventional picture of a DW acting simply as a scattering barrier. These findings identify an interference mechanism in magnetoacoustic transport and point to a route toward frequency-tunable SAW devices based on magnetic domain structures.

Using the density functional theory plus dynamical mean-field theory ($\mathrm{DFT}+\mathrm{DMFT}$) approach, we study the effects of electronic correlations and doping on the normal state electronic structure of the double-layer nickelate superconductor ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ (LNO) under pressure. In agreement with experiments, we obtain significant orbital-dependent quasiparticle renormalizations of the Ni $x^2\text{−}{y}^2$ and $3z^2\text{−}{r}^2$ bands, accompanied by incoherence (bad metal behavior) of the $3z^2\text{−}{r}^2$ states, caused by the proximity of the Ni $3d$ states to orbital-dependent localization. Our results demonstrate a sensitive, nonmonotonic dependence of $m^{*}/m$ on doping, with a remarkable, by about 20%, increase for the Ni $x^2\text{−}{y}^2$ orbitals upon electron doping $x\sim 0.2$ (per Ni ion), implying a significant enhancement of orbital-dependent correlations with oxygen deficiency in LNO. We observe a reconstruction of the low-energy electronic structure of LNO upon doping above $x\sim -0.3$ and 0.2. It is associated with the Lifshitz transition, with a crossover to a self-doping regime characterized by partial occupation of the La $5d$ bands (upon an electron doping $x>0.2$). Our analysis of the static magnetic susceptibility $\chi \left(\mathbf{q}\right)$ obtained within $\mathrm{DFT}+\mathrm{DMFT}$ suggests the possible formation of the spin and charge (or bond) density wave stripes, implying strong spin and charge correlations in LNO. We show that this behavior is associated with the suppression of the Néel $G$-type antiferromagnetic ordering of the ${\mathrm{Ni}}^{2+}$ ions upon hole doping. Interestingly, upon a moderate electron doping of the ${\mathrm{Ni}}^{2.5+}$ ions (e.g., with oxygen deficiency), we find a significant enhancement of the strength of in-plane spin and charge fluctuations. We note a close resemblance of our results to those for the bilayer Hubbard model, which shows the boosting of superconductivity as one of the two electron bands approaches the Lifshitz transition (e.g., upon doping). Our results suggest that spin and charge stripe fluctuations, effectively tuned by doping, play a key role in pressure-driven superconductivity in LNO.

We study electronic properties of the ternary tellurides ${\mathrm{TaXTe}}_4$ (X = Rh, Ir) using density functional theory and investigate chiral anomaly mediated planar Hall response from ab initio calculations. We show that ${\mathrm{TaRhTe}}_4$ is a hybrid Weyl semimetal (WSM), hosting Weyl points (WPs) of both type-I, type-II, and ${\mathrm{TaIrTe}}_4$ is a type-I WSM in absence of spin-orbit coupling (SOC). ${\mathrm{TaRhTe}}_4$ continues to remain a hybrid WSM while ${\mathrm{TaIrTe}}_4$ converts into a type-II WSM under the application of SOC. We observe long Fermi arcs connecting WPs of opposite chirality. We report orbital-driven topological phase transition in ternary tellurides. The WSM phases in ${\mathrm{TaXTe}}_4$ are controlled by the orbital character of the $d_{xz}$ and $d_{z^2}$ states of X = Ir/Rh atoms. Replacing Rh with Ir enhances the $d_{z^2}$ orbital contribution near the Fermi level at the expense of $d_{xz}$ states. This transforms the type-I WPs into type-II resulting in a conversion of hybrid WSM ${\mathrm{TaRhTe}}_4$ to type-II WSM ${\mathrm{TaIrTe}}_4$. This systematic study opens new routes for engineering topological materials relying beyond strong SOC and sheds light on the effect of orbital degree of freedom on the electronic properties of tellurides. We further report an enhancement of planar Hall effects due to orbital-driven topological phase transition in ${\mathrm{TaXTe}}_4$ and we resort to a tight-binding model to correlate the above findings with the velocity modulated off-diagonal effective mass anisotropy in different types of WSMs.

The anomalous Hall effect (AHE) with multi-degree-of-freedom coupling has become a research hot spot in the condensed matter field due to its multiple tunable states, and exploring effective tuning methods for spin, valley, and layer degrees of freedom holds significant research value. Through the first-principles calculations and symmetry analysis, we investigate the properties of bilayer altermagnetic (AM) material $\mathrm{Ca}{\left(\mathrm{CoN}\right)}_2$, which is protected by $S_{4z}$ symmetry, with a particular focus on the influence of interlayer coupling and sliding on the band structure. For bilayer $\mathrm{Ca}{\left(\mathrm{CoN}\right)}_2$ with interlayer antiferromagnetic (AFM) coupling, the interlayer opposite spin sublattices can be connected by symmetries such as $S_{4z}$, classifying it as an AM system. In contrast, systems with interlayer ferromagnetic (FM) coupling belong to the fully compensated ferrimagnetism category. Interlayer sliding breaks the $S_{4z}$ symmetry of the system, thereby controlling the coupling of spin, valley, and layer degrees of freedom. Sliding along the $x$ or $y$ axis breaks the $S_{4z}$ symmetry, inducing opposite valley polarization and layer polarization, which further leads to layer-locked Berry curvature and spin-valley-layer polarized AHE. Bilayer systems with interlayer AFM coupling can switch the spin, valley, and layer degrees of freedom via sliding, while those with interlayer FM coupling can only switch the valley and layer degrees of freedom. This work reveals the sliding rules of bilayer AM systems protected by $S_{4z}$ symmetry and expands the implementation methods for AHE with multi–degree of freedom tunability.

Accurate phonon transmission coefficients are essential for controlling heat transport and designing phononic metamaterials. Conventional models for computing transmission coefficient are based on plane-wave solution and spectrum weighting, limiting their ability to capture actual phonon transport dynamics in multi-interface heterostructures. Here we develop an analytical framework that incorporates spatial coherence and validate it against time-domain wave-packet simulations. We show that spatial coherence strongly affects transmission in multi-interface systems, whereas it is negligible for a single interface. The developed framework is robust for various wave-packet profiles and can accurately resolve both transmission coefficient and the wave-packet dynamics in realistic multi-interface heterostructures. Our work provides a robust framework for exploring coherence effects in phonon transport, which may offer guidelines for thermal management and design of phononic metamaterials.

We present a finite-strain model that is capable of describing the large deformations in bent nanowire heterostructures. The model incorporates a nonlinear strain formulation derived from the first Piola-Kirchhoff stress tensor, coupled with an energy functional that effectively captures the lattice-mismatch-induced strain field. We use the finite element method to solve the resulting partial differential equations and extract cross-sectional maps of the full strain tensor for both zinc-blende and wurtzite nanowires with lattice-mismatched core and one-sided stressor shell. In either case, we show that the bending is essentially exclusively determined by ${\varepsilon }_{zz}$. However, the distinct difference in shear strain has important consequences with regard to both the mechanical deformation and the existence of transverse piezoelectric fields in the nanowires.

The exact dynamics of many-particle quantum systems coupled to an environment is governed by the Kadanoff-Baym equations, which describe the time evolution of Green's functions containing both population and spectral information. While these equations can, in principle, be solved exactly for small systems, the numerical cost grows rapidly and becomes prohibitive for longer times or larger systems. Beyond many-body correlations, the primary computational challenge arises from memory effects, which cause the numerical complexity to scale cubically with physical time. In certain cases, this scaling can be reduced to linear by reconstructing the lesser and greater Green's function components from the electron density, however, at the expense of losing spectral information. It is demonstrated here that the Kadanoff-Baym equations for open systems can be solved numerically exactly with optimal quadratic time scaling, without introducing any approximations. This result significantly extends the feasibility of nonequilibrium simulations and provides a simple, exact benchmark for testing approximate methods.

We studied double-layer $\mathrm{WS}{\mathrm{e}}_2$ stacked on opposite sides of thin layers of hexagonal Boron nitride with different densities of electrons and holes. For a fixed hole density, the Coulomb drag resistance is found to exhibit plateaus approximately equal to −$h$/($4e^2$) and −$h$/($2e^2$) as the electron density is changed. When the number of electrons is equal to the number of holes, an exciton solid forms whose transport of quantum edge defects gives rise to the drag resistance. When the electron and hole densities are different, the excess electrons form a solid embedded in the exciton solid. The Coulomb drag resistance of the exciton solid comes from the one-dimensional transport of the two lowest energy channels of quantum edge vacancy-interstitial pairs. This corresponds to the first plateau. With the embedded solid, one of these channels is blocked. This corresponds to the second plateau. Transport experiments in the Corbino geometry with no edges and extra heavier holes were carried out. The plateaus disappeared. Three peaks in the resistance at different hole densities were observed. We interpret that the three peaks correspond to the commensurate exciton and two classes of hole solids. We performed phonon calculations of these states and found that the stability of these exciton-based quantum solids shows good agreement with experiment. Our results establish classes of extreme quantum solid states, opening additional avenues for the study of strongly correlated quantum transport phenomena involving quantum defect states.

$\mathrm{Hf}{\mathrm{O}}_2$ thin films are recognized as pivotal materials for next-generation ferroelectric memories, and extensive experimental efforts have been dedicated to defect-engineering $\mathrm{Hf}{\mathrm{O}}_2$-based systems towards tailored ferroelectric properties. However, the microscopic mechanisms through which excess electrons modulate the defect states and doping behavior in $\mathrm{Hf}{\mathrm{O}}_2$ remain not fully understood, which has slowed progress in the field. To fill this gap, we investigate the interaction mechanisms between aliovalent dopants and oxygen vacancies ($V_{\mathrm{O}}$) in $\mathrm{Hf}{\mathrm{O}}_2$ by subspace corrected (PBE+$U$ functional) density functional theory simulations. Our results reveal that the extra charge introduced by trivalent dopants forms a small polaron localized on a tricoordinated oxygen atom, producing a deep empty defect state within the $\mathrm{Hf}{\mathrm{O}}_2$ band gap. This deep defect state can interact with the excess electrons generated by oxygen vacancies, thereby enhancing the stability of the three-coordinated oxygen vacancy ($V_{\mathrm{O}3}$) configuration compared to the four-coordinated one ($V_{\mathrm{O}4}$). The introduction of $V_{\mathrm{O}4}$ lowers the local polarization-switching barrier near a statistical accumulation of vacancies by 13%, while $V_{\mathrm{O}3}$ produces a more pronounced reduction of 60%, corresponding to a minimum barrier of 0.12eV/u.c. The stabilized $V_{\mathrm{O}3}$ center effectively reduces the ferroelectric switching barrier in the $\mathrm{Pca}{2}_1$ phase by promoting reduced atomic displacements and lattice distortions, significantly decreasing the coercive field of $\mathrm{Hf}{\mathrm{O}}_2$. These findings provide critical insights for advancing the fundamental understanding of $\mathrm{Hf}{\mathrm{O}}_2$ materials and establishing design guidelines for constructing defect-tolerant ferroelectric devices through targeted defect engineering.

Research on twin boundaries (TBs) in molecular crystals has primarily emphasized their effect on mechanical properties and applications, with limited focus on microstructural details. Twin identification typically relies on extensive experiments, lacking reliable computational predictions. Here, we extend to molecular crystals the previously developed evolutionary methodology for predicting grain boundary structures in atomic crystals. To achieve that, care must be taken of molecular orientations, conformations, and grain displacements during global optimization. We apply this method to predict possible TBs on the (100), (010), and (001) planes of polymorph I of aspirin; the (100), (010), (001), (102), (110), and (210) planes of α-RDX; and the (010), ($10\overline{1}$), (011), (101), and (110) planes of β-HMX. For HMX, the lowest-energy (101) TB matches experimentally reported twin, validating our approach. We predict unexpected low-energy TB configurations, including a unique cluster-like structure on (100) plane of aspirin and numerous conformational changes in RDX. Finally, we discuss the characteristics and patterns of molecular crystal twin formation.

Unraveling the mechanisms of ergodicity breaking in complex quantum systems is a central pursuit in nonequilibrium physics. In this work, we investigate a one-dimensional spin-1 model featuring a tunable long-range hopping term, $H_n$, which introduces nonlocal interactions and bridges the gap between Hermitian and non-Hermitian regimes. Through a systematic analysis of level-spacing statistics and Krylov complexity, we demonstrate that $H_n$ acts as a universal control parameter driving the transition from integrability to quantum chaos. Specifically, increasing the strength of $H_n$ induces a crossover from Poissonian to Gaussian orthogonal ensemble statistics in the Hermitian limit and similarly triggers chaotic dynamics in the non-Hermitian case. Most remarkably, despite the onset of global chaos, we identify a tower of exact nonthermal eigenstates that evade thermalization. These states survive as robust quantum many-body scars, retaining low entanglement and coherent dynamics even under strong non-Hermitian perturbations. Our findings reveal a universal mechanism by which long-range and non-Hermitian effects reshape quantum ergodicity, offering pathways for preserving quantum coherence in complex many-body systems.

Changes in magnetic dynamical characteristics accompanying slowing of spin relaxation below 100 K and freezing of spins detected by muon and neutron diffractions have been found. Magnetic phases identified in CrSBr single crystals by slow magnetization relaxation are caused by stepwise changes in magnetic field, alternating current (ac) magnetic susceptibility, and recording of the first-order reversal curve (FORC). “Slow” magnetic relaxation $\sim {10}^3$ s and FORC highlight spin transition effect on magnetic viscosity and domain dynamics. Below 40 K magnetization reversal is due to nucleation, while above 100 K domain propagation is origin of magnetization reversal. ac susceptibility in the 1- to 100-ms time window indicates gradual temperature-dependent changes in the frequency-independent susceptibility peak, identifying both the Néel temperature ($T_{\mathrm{N}}=132\mathrm{K}$) and thermal fluctuation slowing in the 40 K to 100 K range. Field-dependent magnetic susceptibility indicates spin-flop transitions from the antiferromagnetic to the canted state and to ferromagnetic spin configuration. Changes in magnetization reversal mechanism accompanying spin freezing highlight contribution of spin dynamics and spin relaxation to domain wall dynamics.

Transition metal dichalcogenides (TMDs) enable magnetic property engineering via intercalation, but stoichiometry-structure-magnetism correlations remain poorly defined for Fe-intercalated ${\mathrm{NbSe}}_2$. Here, we report a systematic study of ${\mathrm{Fe}}_x{\mathrm{NbSe}}_2$ across an extended composition range $0.05\le x\le 0.38$, synthesized via chemical vapor transport and verified by rigorous energy-dispersive x-ray spectroscopy (EDS) microanalysis. X-ray diffraction, magnetic, and transport measurements reveal an intrinsic correlation between Fe content, structural ordering, and magnetic ground states. With increasing $x$, the system undergoes a successive transition from paramagnetism to a spin-glass state, then to long-range antiferromagnetism (AFM), and ultimately to a reentrant spin-glass phase, with the transition temperatures exhibiting a nonmonotonic dependence on Fe content. The maximum Néel temperature ($T_{\mathrm{N}}=175\mathrm{K}$) and strongest AFM coupling occur at $x=0.25$, where Fe atoms form a well-ordered $2a_0\times 2a_0$ superlattice within van der Waals gaps. Beyond $x=0.25$, the superlattice transforms or disorders, weakening Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions and significantly reducing $T_{\mathrm{N}}$. Electrical transport exhibits distinct anomalies at magnetic transition temperatures, corroborating the magnetic state evolution. Our work extends the compositional boundary of Fe-intercalated ${\mathrm{NbSe}}_2$, establishes precise stoichiometry-structure-magnetism correlations, and identifies structural ordering as a key tuning parameter for AFM. These findings provide a quantitative framework for engineering altermagnetic or switchable antiferromagnetic states in van der Waals materials.

The phase diagram and spin excitation spectra of the Kitaev-Heisenberg model with bond anisotropy are investigated using the exact diagonalization algorithm and spin cluster perturbation theory. By adjusting the model parameters and anisotropy intensity, we comprehensively map the complete phase diagram and uncover the excitation spectral characteristics of each phase. Besides the Kitaev spin liquid phases, whose excitation spectra appear entirely as a continuum, the antiferromagnetic Néel and zigzag phases also display strong high-energy continua and significant renormalization of the magnon dispersions. In contrast, the magnon dispersions of the ferromagnetic and stripy phases align closely with the predictions of linear spin-wave theory. Bond anisotropy induces directional selectivity of the magnetic moments in the four magnetically ordered phases, depending on the interaction parameters. Furthermore, bond anisotropy lifts the gaplessness of the pseudo-Goldstone mode for magnetization along the $z$ axis, while maintaining the gapless nature for magnetization perpendicular to the $z$ axis. Our results demonstrate that quantum fluctuations do not destroy the gapless property, which may be inherited from the gapless phase in the one-dimensional limit, described by a conformal field theory with central charge $c=1$.

We investigate the possibility of engineering dissipatively long-range order that is robust against heating in strongly interacting fermionic systems, relevant for atoms in cavity QED. It was previously shown [Tindall et al. Phys. Rev. Lett. 123, 030603 (2019)] that it is possible to stabilize long-range order in a Hubbard model by exploiting a dissipative mechanism in the Lindblad limit, this latter being valid for spectrally unstructured baths. Here, we first show that this mechanism still holds when including additional spin-exchange interactions in the model, that is, for the tUJ model. Moreover, by means of a Redfield approach that goes beyond the Lindblad case, we show how the stability of the engineered state depends crucially on properties of the bath spectral density and discuss the feasibility of those properties in an experiment.