The generation of spin currents and their use in controlling magnetic states are central to spintronics. In particular, out-of-plane spin polarization is highly desirable for ultrahigh density, low-power magnetic memory because it enables field-free switching of perpendicular magnetization. This can be achieved through low-symmetry crystals and symmetry-broken interfaces, which generate out-of-plane spin currents, enabling deterministic field-free switching. In this work, we investigate the spin-orbit torque (SOT) in high-quality epitaxial ${\mathrm{MnPd}}_3$ films grown on MgO substrates, with a particular emphasis on the role of crystal symmetry in generating unconventional spin polarizations. Our measurements reveal a conventional SOT arising from the $y$-polarized spin current, along with unconventional SOT originating from the $x$- and $z$-polarized spin currents. By injecting charge currents along different crystal orientations, we further reveal a strong correlation between the unconventional torques and crystal orientation. Notably, the damping-like torque generated by the out-of-plane polarized spin current is found to comprise two distinct contributions: a bulk contribution and an interfacial one. Even after the insertion of a Cu spacer layer, this significant damping-like torque efficiency persists. This work provides valuable insights for designing and optimizing spintronic devices with enhanced performance.

We investigate magnetization dynamics in time-varying ferrimagnetic (or ferromagnetic) media (TVFMs) arising from temporal modulation of the bias magnetic field. Within the Landau-Lifshitz-Gilbert framework, we derive the full time-domain magnetic susceptibility without invoking the commonly used instantaneous-response or adiabatic approximations. The resulting susceptibility inherently includes memory and dispersion effects. The theory is further developed for sinusoidally modulated bias, showing how the magnetization harmonics follow Bessel-function weighting, thus enabling precise spectral shaping. We demonstrate that hundreds of harmonics can be generated with controlled energy concentration in selected orders. The propagation characteristics and band structure of Bloch waves in a bulk TVFM (with longitudinal modulation) are found, revealing a modulation-induced momentum band gap. We finally demonstrate scattering from a TVFM slab and show that the spectrum of the scattered field directly mirrors the harmonic spectrum predicted by the magnetization dynamics, with exact harmonic-amplitude correspondence in thin slabs.

The onset of decoherence in open many-body systems lacks a dynamical timescale grounded in the loss of bipartite entanglement. Here, we introduce the geometric decoherence time, defined as the earliest moment the monotone relation between logarithmic negativity and Rényi-$\frac{1}{2}$ entropy—exactly equal across any bipartition for pure states—breaks down under open-system evolution, signaling entropy growth without accompanying entanglement growth. We establish this criterion in both single-particle Gaussian dynamics and many-body Lindbladian evolution. We show that quantum mutual information provides a complementary long-time diagnostic: Its asymptotic vanishing is equivalent to factorization of the steady state across the bipartition, a condition strictly stronger than separability, and whenever a product steady state is approached exponentially in trace norm, negativity and mutual information share the same decay rate. In the presence of a strong symmetry, this tracking can fail—residual classical correlations can survive after entanglement has vanished. In the Kitaev chain with balanced gain and loss, we derive a closed-form solution and show that the topological phase sustains longer coherence times than the trivial phase at identical dissipation, with a local minimum at the chiral-symmetric point. In the interacting XXZ chain, exact many-body evolution shows that local $Z$ dephasing preserves residual classical correlations, whereas gain and loss restore the mutual-information tracking of negativity. Our results establish the geometric decoherence time as a dynamical scale tracking the onset of decoherence.

Recent years have witnessed significant progress in the entanglement-based characterization of quantum phases of matter. The primary objects of interest are the reduced density matrix and its associated entanglement Hamiltonian. As intrinsic properties of a quantum state, these quantities theoretically determine all experimentally accessible local observables. In this work, we investigate the response of two entanglement measures to the real-time dynamics driven by the entanglement Hamiltonian, a process known as modular flow. We demonstrate that our results can be unified into a single generating function, $\langle {\rho }_{AB}^{\alpha }{\mathrm{e}}^{\lambda Q_{AB}}{\mathrm{e}}^{\mu Q_{BC}}{\rho }_{BC}^{\beta }\rangle$. This function is of independent interest because it represents a generalization of the recently proposed Rényi modular commutator. In appropriate limits, this function yields the response of Rényi entropy and its charged version, which we find to be uniquely determined by chiral topological invariants, specifically the chiral central charge and the Hall conductance. Our analytical findings are validated through two independent approaches: (1) free fermion systems using the real-space Chern number formula and (2) an effective field theory treatment that regularizes the entanglement cut via chiral conformal field theory. Both methods yield consistent results.

Achieving purely electrical manipulation of valley degrees of freedom, independent of magnetic fields, represents a critical milestone for next-generation nonvolatile electronics. Using first-principles calculations, we establish bilayer ${\mathrm{CuCrP}}_2{\mathrm{S}}_6$ as a robust platform for such control, driven by the interplay between ferroelectricity and antiferromagnetism. In the ferroelectric state, broken inversion symmetry and spin-orbit coupling induce a single-spin valley-polarized state with a 20.34 meV splitting, enabling an anomalous valley Hall effect where carrier spin is locked to polarization. Conversely, the antiferroelectric state restores effective parity-time symmetry, suppressing macroscopic splitting. However, we uncover a nontrivial hidden Berry curvature in this regime that generates a layer Hall effect characterized by layer-contrasting spin currents. Our findings demonstrate that electrically toggling between ferroelectric and antiferroelectric orders reversibly switches the system between a spin-polarized valley transport regime and layer-selective transport, facilitating valleytronic logic operations without external magnetic fields.

A central challenge in non-Hermitian sensing is that spectral singularities simultaneously amplify both the signal and environmental noise. We address this predicament in a double-chain Hatano-Nelson model featuring unidirectional interlayer coupling. At the exceptional-deficiency (ED) limit, the system exhibits a macroscopically degenerate complex spectrum and a pronounced non-Hermitian skin effect (NHSE), yielding a sensitivity that scales exponentially with lattice size $N$ while remaining robust across a six-order-of-magnitude detuning range. By introducing diagonal spatial disorder, we demonstrate that the NHSE is progressively suppressed, whith eigenspace cosine similarity analysis quantifying a well-defined fault-tolerance threshold. To reconcile the sensitivity-noise trade-off, we delineate at-ED and off-ED operating regimes. While the at-ED configuration imposes fractional-order noise amplification [signal-to-noise ratio (SNR) $\propto {\delta }^{-1/2}$] that saturates at a suboptimal plateau, migrating to the off-ED regime eliminates this geometric singularity and restores a linear scaling law (SNR $\propto {\delta }^{-1}$), achieving an SNR enhancement of several orders of magnitude. Crucially, this improvement is achieved while fully preserving the exponential sensitivity scaling, albeit at a slightly reduced absolute sensitivity compared with the strict at-ED limit. Our findings establish the off-ED framework as a concrete paradigm for next-generation topological sensors that reconcile extreme sensitivity with robust noise immunity.

Using the Kohn-Sham (KS) inversion method of Hollins et al. [J. Phys.: Condens. Matter 29, 04LT01 (2017)], we invert densities from variational and diffusion quantum Monte Carlo (QMC) calculations to obtain benchmark QMC-KS potentials for a range of insulators and semiconductors, which we then compare to the KS potentials of popular density functional approximations (DFAs). Our results show that different DFAs yield similar electron densities, despite differences in their KS potentials, which originate primarily from the exchange and correlation contribution. We also find that the KS gap from the QMC density is typically larger than the KS gaps of most DFAs, with the exception of Hartree-Fock. Finally, the KS gap is sensitive to the inclusion of semicore states in the pseudopotentials, such that comparison with experiment should be done with caution.

Yttrium iron garnet (${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$) is a prototypical ferrimagnetic insulator widely used in spin-wave and magnonic devices owing to its extremely low magnetic damping and long magnon propagation length, and recent experiments suggest that lattice vibrations can influence magnetic properties, motivating a microscopic understanding of how phonons modify exchange interactions. In this work, phonon-driven tuning of exchange interactions in ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ is investigated from a mode-resolved perspective based on first-principles calculations. We focus on how optical phonons modify the dominant superexchange pathways and how lattice distortions affect the Fe-O-Fe bond geometry that governs the exchange interaction. To this end, phonon modes are computed from density functional theory, and the exchange interactions are evaluated from a Wannier-based tight-binding model and mapped onto a spin Hamiltonian, while displaced structures along individual infrared-active modes are used to quantify their impact on the magnetic interactions.

We investigate thermal Hall transport in magnetic systems, using semiclassical spin dynamics simulations. Building on a linear response framework, we discuss the intricacies of computing the thermal Hall conductivity from real-time energy current correlations and the energy magnetization. We then apply this methodology to two models: a square-lattice chiral magnet with in-plane Dzyaloshinskii-Moriya interaction, and the antiferromagnetic Kitaev model in a field. Our results demonstrate the efficiency of semiclassical spin dynamics to study thermal Hall transport capturing quantitative effects beyond the simple intrinsic noninteracting approximation. They can serve as a benchmark for comparison with experiments in regimes where nonlinearities from magnon-magnon interactions and strong thermal fluctuations play a crucial role.

We calculate the theoretical nondegenerate two-photon absorption and three-color injected current response tensors for bulk GaAs and ${\mathrm{Ge}}_{1-x}{\mathrm{Sn}}_x$ for a range of alloy compositions. In particular, by including a “pump” beam we compare two “schemes” that are sensitive to midinfrared photons. In scheme I we consider GaAs and a pump photon with energy greater than half the band gap, and in scheme II we consider ${\mathrm{Ge}}_{1-x}{\mathrm{Sn}}_x$ with a pump photon with energy less than half the band gap. We find that for certain pump and alloy concentrations ${\mathrm{Ge}}_{1-x}{\mathrm{Sn}}_x$ has a substantially larger nonlinear response and three-color injected current than GaAs in the midinfrared frequency window where both materials can absorb photons via nondegenerate two-photon absorption.

Analytical treatments of tunneling in bilayer graphene have typically relied on minimal models including only the vertical interlayer hopping ${\gamma }_1$ and have been restricted to the weak interlayer-bias regime ($2\varepsilon \ll {\gamma }_1$). Consequently, they cannot adequately describe lattice deformations or strong electric-field effects. In this work, we present an analytical theory of evanescent states in electrically gapped bilayer graphene that overcomes both limitations. Our approach explicitly incorporates the skew interlayer hoppings ${\gamma }_3$ and ${\gamma }_4$ and remains valid even when the interlayer bias $2\varepsilon$ is comparable to ${\gamma }_1$. Focusing on low-energy electronic states near the charge neutrality point, we analytically derive the complex longitudinal wave numbers, the gap width, and the sublattice pseudospin within the electric-field-induced gap. We then systematically analyze the dependence of these quantities on the interlayer shear displacement $\vec{\delta }=({\delta }_x,{\delta }_y)$, and find that skew interlayer hoppings, in particular ${\gamma }_3$, play an essential role. For transport along the zigzag ($x$) direction, the longitudinal wave vector becomes complex, whereas the transverse wave vector remains real. For a monolayer/bilayer/monolayer junction with transport along the zigzag direction, we find that ${\delta }_y$ has a significantly stronger impact on the conductance than ${\delta }_x$. Furthermore, we identify a shear-induced phase proportional to ${\delta }_y$ that appears universally in the analytical expressions for the gap width, the sublattice pseudospin, and the decay length. These results establish a unified framework for shear- and bias-controlled evanescent tunneling in bilayer graphene and suggest broader relevance to nonequilibrium transport phenomena in layered materials.

Moiré superlattices host a rich variety of correlated topological states, including interaction-driven integers and fractional Chern insulators. A common approach to study interacting ground states at integer fillings is the Hartree-Fock mean-field method. However, this method neglects dynamical correlations, which often leads to an overestimation of spontaneous symmetry breaking and fails to provide quantitative descriptions of single-particle excitations. This work introduces a general many-body perturbation framework for moiré systems, combining all-band Hartree-Fock calculations with $GW$ quasiparticle corrections and random-phase approximation (RPA) correlation energies. We apply this framework to hexagonal boron nitride-aligned rhombohedral pentalayer graphene and magic-angle twisted-bilayer graphene (MATBG). We show that incorporating RPA correlation energy and $GW$ self-energy corrections yields phase diagrams and single-particle spectra that quantitatively align with experimental measurements for both systems. Particularly, the ground state at charge neutrality of MATBG is predicted to be a nematic metal, which is stabilized over Kramers intervalley coherent insulator due to lower correlation energy. Our versatile framework provides a systematic beyond-mean-field approach applicable to generic moiré systems.

Phonons can carry angular momentum and exhibit chirality through the circular polarization of atomic motion. This enables a phonon-mediated spin Seebeck effect (SSE) via the conversion of phonon angular momentum into electron spin angular momentum. In this Letter, we develop a theoretical framework for calculating the spin current in a normal-metal–chiral-insulator (NM-CI) heterostructure within the nonequilibrium Green's function formalism. We discuss the influence of (i) the thermal bias across the NM-CI interface, (ii) the chemical potential of the NM, and (iii) the modification of the interfacial on-site potential on the spin-transport properties. We identify two characteristic nonlinear spin-transport phenomena: negative differential SSE and spin-current rectification. The negative differential SSE arises from the competition between the thermal bias and the density of thermally excited electrons. Spin-current rectification suggests the possibility of realizing a thermally controlled spin diode. We also find that the spin-transport behavior is closely associated with an effective interfacial spectral density. This work suggests an alternative route toward thermally controlled spintronic devices using chiral phonons.

The quantum anomalous Hall (QAH) effect is usually realized through ferromagnetism or magnetic doping, which limits material choices and often results in low mobility, disorder sensitivity, and low operating temperatures. Here, we propose a mechanism to achieve the QAH phase without net magnetization, using altermagnetic exchange on a weak topological insulator (WTI). The altermagnetic order selectively gaps the Dirac cone at the $Z$ point, while hybridization between the top and bottom surfaces of the WTI thin film opens a trivial gap at the $\mathrm{\Gamma }$ point, generating a Chern number $\mathcal{C}=1$ phase with a single chiral edge channel. We verify the topological transition through both a minimal thin-film model and a slab geometry, and compute the associated Hall response. As altermagnets and layered WTIs already exist experimentally, this mechanism offers a promising and experimentally accessible route to realizing QAH phases without magnetic doping or global magnetization. The results indicate that altermagnetic surface engineering may provide a clean and controllable pathway for realizing dissipationless edge transport in layered quantum materials.

We study the local density of states (LDOS) distribution of a general class of weighted Erdős-Rényi graphs. Using the cavity method, we obtain a good approximation to the full LDOS distribution and compact expressions for its power-law tails, which we show to have exponent 3 in the extended phase. We deduce that the eigenvectors in the continuous part of the spectrum are extended but (weakly) multifractal, and we extract expressions for the associated fractal dimensions and the singularity spectrum. We also demonstrate that the inverse participation ratio in this multifractal phase exhibits an unusual logarithmic scaling with system size, which is neither fully extended nor localized by the usual definitions. Finally, we verify that some symmetry properties (derived from the nonlinear sigma model), which have been shown to hold for many systems exhibiting multifractality, also hold in our case, both for the LDOS distribution and the singularity spectrum.

A transition from crystal-field to spin wave excitations has been experimentally observed in ${\mathrm{PrFeO}}_3$ using inelastic neutron scattering. Theoretical modeling with density functional theory and the mean field random phase approximation successfully reproduces the experimental observations and allows extraction of the values for the various exchange interactions. The study reveals that the strong coupling between the two magnetic sublattices of Pr and Fe is the fundamental mechanism underlying the low-temperature Pr magnetism. This coupling, analogous to the Dicke cooperative interaction between atoms and photons, polarizes the Pr moments, enhances the Pr-Pr interactions, and contributes to the formation of a quasidoublet, leading to the transition from single-particle to collective excitations within the Pr sublattice. Furthermore, this coupling induces spin reorientation on the Fe sublattice. The manipulation of magnetic moments via spin waves is achievable through the coupling between different magnetic sublattices in a bulk material containing multiple magnetic ions.

We present the global topological phase diagram of a two-dimensional electron gas placed in a quantizing magnetic field and proximitized by a superconducting vortex lattice. Our theory allows for arbitrary ratios of the pairing amplitude, magnetic field, and chemical potential. By analyzing the Bogoliubov-de Gennes Hamiltonian, we show that the resulting phase diagram is highly nontrivial, featuring a plethora of topological superconducting phases with chiral edge modes of quasiparticles. Landau-level mixing plays an essential role in our theory: Even in the weak-pairing limit, it generically splits the integer quantum Hall transition lines into a sequence of transitions with larger Chern number jumps of both signs protected by the symmetries of the superconducting vortex lattice. Interestingly, we find that weak pairing induces trivial or topological superconductivity when chemical potential is tuned to a Landau-level energy, depending on the Landau-level index.

Triangular-lattice rare-earth chalcogenides $\mathrm{NaYb}{X}_2$ ($X$ = O, S, and Se) are promising quantum spin liquid (QSL) candidates, while the exact properties of the quantum state remain elusive. In this work, we present a spin-dynamic investigation of ${\mathrm{NaYbSe}}_2$. Magnetic susceptibility and specific heat reveal pronounced easy-plane anisotropy and short-range spin correlations below 20 K. In the $X$-band and pulsed high-field electron spin resonance (ESR) measurements, the temperature dependence of anisotropic $g$ factors and linewidths illustrate the development of spin correlations at low temperatures. Interestingly, unlike the noninteracting paramagnets showing linear frequency-field (ν-$H$) behavior through the origin, ${\mathrm{NaYbSe}}_2$ at 2 K exhibits complex dynamical characteristics: The resonance mode evolves from low-field linear ν-$H$ behavior to an easy-plane antiferromagnetic-like (AFM-like) resonance with a gap of 21.06(2) GHz in the intermediate fields and finally reverts to a high-field linear ν-$H$ dependence as the system approaches the magnetic saturation. This phenomenon indicates the suppression of quantum fluctuations by a strong magnetic field, facilitating magnetic-field-induced ordering. Through fitting with the easy-plane AFM-like resonance model, we extracted an effective exchange interaction of $J$ = −1.18 (2) K for ${\mathrm{NaYbSe}}_2$. The ν-$H$ relationship in ESR measurements provides insight for understanding unconventional spin excitations in QSLs of triangular-lattice quantum magnets.