We investigate one-dimensional systems with both energy conservation and a continuous symmetry, focusing on the impact of a boundary perturbation that breaks the continuous symmetry. Our study reveals two distinct dynamical phases: one in which the corresponding charge exhibits extensive fluctuations, and another where the charge remains conserved. These phases appear in both free and interacting models. We interpret this behavior through a boundary-induced pumping mechanism, which estimates the amplitude connecting two degenerate states from different charge sectors via a local charge-nonconserving operator. In the Floquet setting, we show that the frozen phase can survive at high driving frequencies but vanishes at low frequencies. This phenomenon is exact in free-fermion systems in the thermodynamic limit, but in interacting systems it appears only at finite system size. The emergence of the charge-frozen phase is attributed to effective energy conservation, and we demonstrate that this phase disappears when effective energy conservation is broken or replaced by other symmetries.

The classification of collinear magnetic phases in analogy with atomic orbitals and superconducting pairings has long lacked a collinear $p$-wave counterpart—systems exhibiting linear-in-$k$ spin splitting (SS) without net magnetization or spin-orbit coupling. Here, we resolve this gap by identifying a class of compensated magnets, in which antiparallel spins occupy symmetry-inequivalent sites related by a mirror operation. We show that electric dipoles constrained by mirror symmetry enable a magnetoelectric coupling that produces $p$-wave off-centered Fermi surfaces. This mechanism also gives rise to an intrinsic spin and crystal Hall effects as well as directional anomalous Hall response, locked by symmetry to the mirror plane. We derive the enabling symmetry conditions, establish a hierarchy of electric multipolar contributions, and identify by inverse design five prototypical candidates, including the high-pressure triple perovskite ${\mathrm{Mn}}_4{\mathrm{Nb}}_2{\mathrm{O}}_9$ verified via first-principles calculations as a prototypical collinear $p$-wave magnet. Our results unify $s$-, $d$-, and $p$-wave collinear magnets and reveal mirror symmetry as a key ingredient for engineering SS in antiferromagnets.

All-optical switching in a ferromagnetic spin valve is studied here using atomistic spin drift-diffusion dynamics, which includes contributions from spin pumping and superdiffusive transport. We find the switching is governed principally by spin-polarized currents due to nonequilibrium hot electrons excited by the laser pulse and reequilibration currents. In particular, an initial superdiffusive forward flow of electrons, polarized by the free layer, is generated. This drives parallel to antiparallel switching of the free layer through accumulation of minority spins at the reference layer. A diffusive backward flow of electrons, repolarized by the reference layer, follows the initial superdiffusive flow as the charge distribution reequilibrates. Due to the pulse width-dependent asymmetric amplitudes of the forward and backward transients, the latter can drive antiparallel to parallel switching, and create multidomain structures at higher laser fluences and longer pulses. The results obtained here are in agreement with experimental observations, providing a framework for self-consistent modeling of all-optical switching in metallic heterostructures.

Classical spin liquids are frustrated magnetic phases characterized by local constraints, flat bands in reciprocal space, and emergent gauge structures with distinctive signatures such as pinch points. These arise generally in cluster systems, where spin interactions can be expressed as constraints on clusters of spins. In this work we present the different generic rules allowing to build such cluster systems together with a few tools allowing to quickly characterize it. We show that based on these rules, it is possible to conceive a tunable recipe for generating such models by decorating a parent lattice on its bonds and/or vertices with symmetry-compatible clusters. This approach highlights a key design trade-off: Using fewer cluster types increases the number of flat bands and enhances spin-liquid behavior but produces denser connectivity that is harder to realize experimentally. The framework is highly tunable, extends naturally to two and three dimensions, and provides a versatile toolbox for engineering new classical spin-liquid candidates with targeted features such as higher-rank pinch points or pinch lines. Importantly, decorated cluster lattices constitute an ideal playground for producing multiple flat bands—not only at the spectral bottom but also embedded within the spectrum. This proliferation of flat bands can be understood either from general connectivity arguments or, equivalently, by explicitly constructing compact localized eigenmodes in an associated hopping description.

Unidirectional magnetoresistance (UMR) in metallic bilayers arises from nonlinear spin-charge transport mediated by broken time-reversal and inversion symmetries, yet the role of magnons remains unsettled. We develop a theoretical framework that incorporates coupled electron-magnon dynamics, revealing cross diffusion and spin-angular-momentum transfer between the two subsystems, which renormalize the characteristic electron and magnon spin-diffusion lengths. We show that nonequilibrium magnons, indirectly excited by the electric field, can suppress UMR by absorbing spin angular momentum from conduction electrons. We also analyze the magnetic-field, thickness, and temperature dependencies and identify distinct features that constitute experimental fingerprints of magnonic contributions to UMR in metallic bilayers, providing qualitative to semiquantitative guidance for elucidating the underlying physical mechanisms.

Frustrated magnetic materials provide a fertile ground for exploring novel quantum states, wherein the interplay between spin and lattice degrees of freedom plays a pivotal yet underexplored role. Here, we employ terahertz (THz) time-domain spectroscopy to investigate the spin-lattice coupling and short-range spin correlations in ${\mathrm{NaCrO}}_2$, an $S=3/2$ layered triangular-lattice Heisenberg antiferromagnet. Combined with superconducting quantum interference device magnetometry, our THz spectroscopy reveals the persistence of short-range magnetic order up to twice the long-range magnetic ordering temperature. Furthermore, several low-frequency phonon modes are identified in the THz spectra. Their temperature dependence manifests a strong spin-phonon coupling, characterized by abrupt changes in the intensity and frequency of the phonon absorption peaks at magnetic critical temperatures. Further analysis implies that this coupling is primarily driven by the exchange-interaction-induced modification of the Cr-O bonds. Our work provides direct evidence of spin-phonon coupling in a frustrated magnet and suggests new avenues for manipulating lattice dynamics in quantum materials.

The suppression of density wave in bilayer nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ under pressure has been identified as a critical factor enabling pressure-induced high-temperature superconductivity. However, this density wave state exhibits remarkable stability against most alternative tuning methods except the high-pressure technique. Herein through systematic investigations of Tb doping effects on electrical transport and magnetic properties, we observe a gradual suppression of density wave transition temperature with the increasing Tb concentration, accompanied by the emergence of negative magnetoresistance persisting up to 14 T. Magnetic susceptibility measurements further reveal the formation of a doping-induced spin-glass state, which likely accounts for the observed negative magnetoresistance phenomenon. This work establishes an effective chemical doping approach to manipulate the density wave state and correlated quantum state in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$, offering new insights into the mechanism of high-temperature superconductivity and potential pathways toward achieving ambient-pressure superconductivity in bulk nickelate crystals.

In this paper we consider the problem of solving quantum field theories with time dependent interaction strengths. We show that the recently formulated framework [P. R. Pasnoori, Phys. Rev. B 112, L060409 (2025)], which is a generalization of the regular Bethe ansatz technique, provides the exact many-body wave function. In this framework, the time-dependent Schrodinger equation is reduced to a set of analytic difference equations and matrix difference equations, called the quantum Knizhnik-Zamolodchikov (qKZ) equations. The consistency of the solution gives rise to constraints on the time-dependent interaction strengths. For interaction strengths satisfying these constraints, the system is integrable, and the solution to the qKZ and the analytic difference equations provides the explicit form of the many-body wave function that satisfies the time-dependent Schrodinger equation. We provide a concrete example by considering the $SU\left(2\right)$ Gross-Neveu model with time dependent interaction strength. Using this framework we solve the model with the most general time-dependent interaction strength and obtain the explicit form of the wave function.

The strongly constrained and appropriately normed (SCAN) meta-generalized gradient approximation (meta-GGA) functional is a milestone achievement of electronic structure theory. Recently, a revised and restored form $\left({\mathrm{r}}^2\mathrm{SCAN}\right)$ has been suggested as a replacement for SCAN in high-throughput applications. Here, we assess the accuracy and reliability of the ${\mathrm{r}}^2\mathrm{SCAN}$ meta-GGA functional for the group-IV elemental solids carbon (C), silicon (Si), germanium (Ge), and tin (Sn). We show that the ${\mathrm{r}}^2\mathrm{SCAN}$ functional agrees closely with its parent functional SCAN for elastic constants, bulk moduli, and phonon dispersions, but the numerical stability of ${\mathrm{r}}^2\mathrm{SCAN}$ is superior. Both meta-GGA functionals outperform standard GGA (Perdew-Burke-Ernzerhof) in terms of accuracy and approach the level of common hybrid functionals (Heyd-Scuseria-Ernzerhof). However, we find that ${\mathrm{r}}^2\mathrm{SCAN}$ performs much worse than SCAN for the $\alpha \leftrightarrow \beta$ phase transition of both Ge and Sn, yielding larger phase energy differences and transition pressures.

We introduce a conceptual reformulation of the Mott-Berezinskiĭ (MB) theory of low-frequency ac conductivity in disordered systems based on localization-landscape theory. Instead of assuming uniform localization and fixed hopping distances, transport is described through an effective potential whose geometry encodes the spatial organization and energy-dependent localization of quantum states. Using the associated Agmon metric, we define a generalized Mott scale that replaces the classical hopping length with a geometric criterion set by the disorder landscape. This framework naturally incorporates strong spatial inhomogeneity and yields the ac conductivity directly from the effective potential. The standard MB result is recovered as a limiting case. Our approach extends the conceptual foundation of MB theory to arbitrary disordered media and energies approaching the mobility edge, providing a unified description of ac transport in complex quantum materials.

Exceptional points (EPs), non-Hermitian degeneracies where eigenvalues and eigenstates simultaneously coalesce, enable exponential energy splitting in response to small perturbations, yielding sensitivity beyond conventional limits. However, EP-based sensors are particularly vulnerable to noise, which can obscure signals and degrade measurement accuracy. Here, we propose a noise-robust sensing scheme. The scheme harnesses the exponential response of EPs, which allows a rapid decay of the noise level when operating slightly off the degeneracy. By synergistically incorporating non-Hermitian directional amplification to exponentially enhance signals, our approach achieves simultaneous high sensitivity and noise resilience. Numerical verification confirms exponential noise reduction compared to direct EP operation. By carefully correlating instrumental parameters, perturbation strength, and noise levels, we establish a comprehensive design framework for sensitivity-robustness optimization. To validate the practical feasibility of this scheme, we further design an acoustic sensing device composed of interconnected cavities, utilizing electro-acoustic coupling as the source of non-Hermitian directional amplification. Simulated results confirm that a moderate-scale, off-EP configuration can achieve both high sensitivity and strong noise robustness. Our strategy overcomes the traditional trade-off between sensitivity and noise resilience, paving the way for practical applications of non-Hermitian EP sensing.

Photoelectrical detection of magnetic resonance (PDMR) offers a scalable alternative to optical readout of spin defects in semiconductors and is particularly promising for near-infrared (NIR) emitters, where photodetection is often challenging. Here, we demonstrate room-temperature coherent PDMR of PL3 (divacancy), PL5, PL6, and PL7 spins. PL7 and PL5 exhibit notably stronger PDMR than PL6 as opposed to optical detection, indicating higher ionization efficiency and suitability for electrical readout. Rabi oscillation and two-frequency spectroscopy reveal a previously undiscovered secondary resonance of PL7. We determine the zero-field splitting parameters of PL7 and assign the recently reported PL3a defect to PL7. The demonstrated PDMR of these NIR defects constitutes a key advancement toward quantum electronic devices. Also, the clarified spin parameters and ionization characteristics provide a solid foundation for advancing quantum technologies utilizing these defects regardless of the detection schemes.

Inertial effects in magnetic relaxation dynamics remain an experimentally unexplored aspect of condensed matter systems with few examples reported in spin ice and ferrofluid compounds. In this work, we examine the relaxation dynamics in chiral magnet ${\mathrm{Co}}_8{\mathrm{Zn}}_7{\mathrm{Mn}}_5$ across magnetic phases. Conventional Debye and Cole-Cole models fail to capture the frequency dependence of ac susceptibility across different magnetic phases, whereas incorporating an inertial component successfully describes the dynamics thereby yielding a consistent relaxation time (τ) of ${10}^{-5}$ s for ${\mathrm{Co}}_8{\mathrm{Zn}}_7{\mathrm{Mn}}_5$. The field-dependent variation of τ exhibits a nonmonotonic nature, with the double-peak-like structure at the skyrmion phase transitions. Our results reveal the presence of inertial effect in magnetic relaxation behavior of β-Mn type Co-Zn-Mn compounds. We demonstrate that the inertial effect is an intrinsic property of β-Mn type Co-Zn-Mn compounds that is independent of any particular magnetic phase. We qualitatively argue that spin fluctuation is the most plausible cause for inertial effects in chiral magnets.

We explore ballistic magnetization reversal by spin-orbit torques (SOTs) using time-dependent electric currents based on reinforcement learning (RL). The learning process is conducted through numerical simulations of single-domain magnetization dynamics, with the profiles of the applied electric currents varying. The RL agent autonomously finds the deterministic and ballistic magnetization reversal without the need for external magnetic fields. The reversal is found to be done by the fieldlike SOT and is less affected by the Gilbert damping and dampinglike SOT. The lower bound time for the magnetization reversal mechanism is evaluated. The robustness against the damping parameters and the effects of the thermal noise field are also discussed.

The valley degree of freedom provides a promising route for functionalizing two-dimensional materials, yet a unified principle for realizing the anomalous valley Hall effect (AVHE) in tetragonal systems under static control has remained elusive. Here, we establish a general symmetry criterion for achieving AVHE in two-dimensional tetragonal magnetic materials through systematic analysis of magnetic layer groups. We demonstrate that finite valley polarization emerges only when type-2/3/4 symmetry operations (constraining Berry curvature and enforcing valley degeneracy) are broken by external fields, while type-1 symmetries are preserved. By screening magnetic layer groups, we identify specific systems in which this condition can be satisfied through perpendicular electric fields and uniaxial strain, and we validate our criterion using first-principles calculations and tight-binding analyses of ${\mathrm{Fe}}_2\mathrm{BeBrP}$ and bilayer ${\mathrm{VS}}_2$. Our results reveal that the symmetry class of a magnetic layer group dictates the minimal control pathway for generating AVHE, thereby providing a unified theoretical framework for spin-valley control and device design in two-dimensional tetragonal magnetic materials.

Magnons have been intensively studied in two-dimensional (2D) ferromagnetic (FM) skyrmion crystals (SkXs) stabilized on Bravais lattices, particularly triangular and square lattices. In these systems, topological edge states (TESs) have been reported in higher-energy magnon gaps, while the first magnon gap is found to be topologically trivial. In this context, antiferromagnetic (AFM) SkXs on the triangular spin lattice have been considered potentially more interesting for applications, since TESs emerge already in the first magnon gap. Meanwhile, the magnon topology of SkXs stabilized on non-Bravais spin lattices remains largely unexplored. In this work, we theoretically investigate the magnon band structure and TESs in 2D FM SkXs stabilized on the honeycomb spin lattice, including experimentally motivated parameter sets relevant to van der Waals magnets. We show that chiral TESs emerge in the first magnon gap over significant ranges of the Dzyaloshinskii–Moriya interaction and single-ion magnetic anisotropy. Magnetic-field-driven topological phase transitions modify the number of these TESs before eventually trivializing them. In addition, we find that TESs can coexist in the first and higher magnon gaps, which could enable frequency-multiplexed magnonic edge transport. These findings highlight the role of lattice geometry in shaping the magnon topology and edge transport in noncollinear spin textures.

The subtle interplay between spin-orbit coupling, exchange interactions, and cation ordering can lead to exotic magnetic states in transition-metal ions. We report a comprehensive study of the Re-based ($5d^1$) ordered double perovskite oxide ${\mathrm{Sr}}_2{\mathrm{ZnReO}}_6$ combining synchrotron x-ray diffraction (XRD), magnetic susceptibility, muon spin relaxation ($\mu \mathrm{SR}$) measurements, and density functional theory (DFT) calculations. XRD reveals that ${\mathrm{Sr}}_2{\mathrm{ZnReO}}_6$ crystallizes in the monoclinic structure (space group $P{2}_1/n$) at low temperature. Magnetic susceptibility data indicate a transition below $\sim 13\mathrm{K}$, with $M–H$ loops showing ferromagnetic-like hysteresis and an unusually high coercive field of 23 kOe at 2 K. Zero-field $\mu \mathrm{SR}$ measurements detect static and spatially disordered internal fields below $T_M\simeq$ 12 K, consistent with a canted antiferromagnetic ground state determined by detailed DFT and force-theorem in Hubbard-I calculations. The reduced high-temperature effective moment ($\sim 0.76{\mu }_B$) and very small static moment ($\lesssim 0.2{\mu }_B$) derived from $\mu \mathrm{SR}$ analysis and local-field simulations indicate a decisive role of spin-orbit coupling. Through a combined experimental and computational approach we unambiguously determine the canted antiferromagnetic order in ${\mathrm{Sr}}_2{\mathrm{ZnReO}}_6$, showing that a very small ordered moment coexists with an exceptionally large coercivity. These results underscore the crucial role of spin-orbit coupling and orbital ordering, providing new insights into magnetism in $5d^1$ double perovskites.