We report the existence of a large set of ferromagnetic scarred states in the one-dimensional transverse-field Ising model with long-range interactions, in a regime with no ferromagnetic phase at finite temperature. These scarred states are distributed over different spectral regions, surrounded by a paramagnetic sea. We show that simple initial conditions, consisting of a few small magnetic domains, selectively populate these scarred states. This leads to the appearance of a special dynamical phase, which we call the scarred ferromagnetic phase. As a consequence, initial states with a small number of small magnetic domains evolve towards ferromagnetic equilibrium states, whereas initial states with larger domains or no magnetic structure relax to the expected thermal paramagnetic equilibrium state.

The one-dimensional (1D) $J_1-J_2$ quantum spin model can be viewed as a strong-coupling analog of the Schrieffer-Su-Heeger model with two inequivalent alternating Ising couplings along the wire, associated to the physics of resonating valence bonds. Similar to the quantum Ising model, which differently presents a long-range Néel ordered phase, this model also maps onto a $p$-wave superconducting wire which shows a topological phase transition with the emergence of low-energy Majorana fermions. We show how signatures of the topological phase transition for the $p$-wave superconducting wire, i.e., a half Skyrmion, are revealed through local (short-range) spin observables and their derivatives related to the capacitance of the pairing fermion model. Then, we present an “edge” correspondence through the edge spin susceptibility in the $J_1-J_2$ model revealing that the topological phase transition is a metal of Majorana fermions. We justify that the spin magnetization at an edge at very small transverse magnetic field is a good marker of the topological invariant and of Majorana zero modes. We identify a correspondence between the quantum information of resonating valence bonds and the charge fluctuations in a $p$-wave superconductor through our method “the bipartite fluctuations”. Physical properties of this 1D model are in fact robust when including additional interactions, which is optimistic for practical applications, e.g., in quantum circuits.

Phase change materials (PCMs) enable the controlled modulation of physical properties through phase transitions induced by external stimuli, including temperature, pressure, irradiation, or electric and magnetic fields. Of particular interest is trititanium pentoxide (${\mathrm{Ti}}_3{\mathrm{O}}_5$), a promising PCM for heat storage, which exhibits a low pressure threshold for the $\lambda$ to $\beta$ phase transition. Although the phase transitions of bulk ${\mathrm{Ti}}_3{\mathrm{O}}_5$ have been extensively studied and well understood, research on its surface properties and associated phase transformations remains limited due to the computational challenge of modeling pressure effects on the surface at the atomic scale. Here we introduce a computational framework that combines a machine-learned interatomic potential trained on high-fidelity density functional theory data with explicit pressure simulation via repulsive slab potentials. We identify a hitherto unknown stable surface reconstruction and a kinetically favorable layer-by-layer transition mechanism. On-the-fly probability enhanced sampling simulations reveal that pressure significantly reduces the free energy barrier, predicting a phase transition at only 700 bar, in good agreement with the experimental value. This work presents a feasible and generally applicable protocol for modeling pressure effects in PCMs, paving the way for improved understanding and application of materials under operational conditions.

Ferroelectric (FE) instability in the puckered lattice of arsenic (α-As) is investigated using density functional theory (DFT) calculations. A bilayer (BL) structure with the most stable AA-stacked configuration is found to exhibit spontaneous ferroelectric polarization arising from an intralayer distortion analogous to that observed in α-Bi monolayers. Unlike conventional two-dimensional (2D) ferroelectricity, which is typically driven by sliding-induced charge transfer, the observed polarization in α-As primarily originates from a lattice contraction along the armchair direction caused by inverted band occupation facilitated through interlayer electron hopping. The calculated polarization reaches $0.63\times {10}^{-10}\mathrm{C}/\mathrm{m}$ with the associated transition barrier 5.4 meV/u.c., and our molecular dynamics simulations using machine-learned interatomic potential show the FE ordering persisting up to ∼100 or 300 K under a uniaxial compression of 0% or −4%, respectively. These results provide new insight into distinct mechanism of 2D ferroelectricity governed by interlayer electronic coupling.

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.