Unconventional odd-parity magnets, characterized by an odd-parity momentum-dependent spin splitting, offer a fundamentally distinct paradigm for noncollinear spintronics. Here, we theoretically investigate the Ruderman-Kittel-Kasuya-Yosida indirect exchange in two-dimensional odd-parity magnets subjected to Rashba spin-orbit coupling. Using an analytical real-space Green's function formalism, we uncover a parity-driven spatial decoupling in the magnetic response. Because of the odd-parity exchange field, the out-of-plane Ising interaction is structurally insulated from the macroscopic magnetic modulation, oscillating isotropically at the shifted Fermi wave vector. Conversely, the in-plane Heisenberg components exhibit pronounced, directionally tunable spatial beating. Beyond collinear exchange, the hybridized bands generate a highly tunable, three-component Dzyaloshinskii-Moriya interaction alongside symmetric off-diagonal anisotropies. We reveal that the out-of-plane chiral twisting is driven by the massive, nonrelativistic momentum shift, while the in-plane chiral components are relativistic. Furthermore, the competition between the nodal geometry and the Rashba gap drives an anomalous, dimension-reducing crossover, in which the in-plane chiral components follow a one-dimensional-like $1/R$ spatial decay along the nodal lines over an extended intermediate-distance window before ultimately recovering the conventional two-dimensional $1/R^2$ asymptote. We demonstrate that these findings hold universally across the odd-parity class by explicitly generalizing our framework to $f$-wave magnets. Finally, numerical tight-binding calculations verify the striking robustness of this parity-driven decoupling against both scalar and random magnetic exchange disorder. These findings establish odd-parity magnets as promising platforms for engineering robust, directionally tunable noncollinear spin textures.

We study the genuine multipartite entanglement (GME) in a disordered system and its potential for detecting the transition from the thermalized to the localized phase. We demonstrate that the quenched average GME can approach its near-maximum value in the ergodic phase of a disordered quantum spin model. In contrast, GME vanishes in the many-body localized (MBL) phase, both in equilibrium and in the long-time dynamical regime, indicating a lack of multipartite entanglement in the localized regime. To establish this, we analyze the disordered Heisenberg spin chain subjected to a random magnetic field along with the two- and three-body Dzyaloshinskii-Moriya (DM) interactions. We show that the behavior of GME, in both the mid-spectrum of the Hamiltonian and the dynamically evolved states from an initial Néel configuration, serves as a reliable indicator of the critical disorder strength required for the ergodic-to-MBL transition. The identified transition point aligns well with standard indicators such as the gap ratio and the correlation length. Moreover, we find that the presence of DM interactions, particularly the three-body interaction, significantly enlarges the thermal phase and delays the onset of localization with an extended correlation length. This shift in the transition point is consistently reflected in both static and dynamical analyses, reinforcing GME as a robust probe for MBL transitions.

Using the $\mathrm{DFT}+$ dynamical mean-field theory ($\mathrm{DFT}+\mathrm{DMFT}$) method, we study the normal-state electronic structure, orbital-dependent quasiparticle renormalizations, Fermi surface, and magnetic correlations in the recently discovered alternating single-layer bilayer hybrid Ruddlesden–Popper nickelate superconductor ${\mathrm{La}}_5{\mathrm{Ni}}_3{\mathrm{O}}_{11}$ (1212-LNO). Our results for the $\mathrm{DFT}+\mathrm{DMFT}$ electronic states exhibit qualitative differences for the structurally distinct single-layer and bilayer Ni ions, implying the importance of confinement and orbital-dependent correlations. The partially occupied Ni $e_g$ electronic states originating from the bilayer Ni ions form strongly renormalized quasiparticle bands with a large enhancement factor $m^{*}/m\sim 3.5$ and 4.2 for the Ni $x^2-y^2$ and $3z^2-r^2$ orbitals, respectively, implying the proximity of the Ni $3d$ states to orbital-dependent localization. Moreover, the $e_g$ states of the single-layer Ni ions exhibit an orbital-selective Mott insulating state, with a narrow energy gap for the Ni $3z^2-r^2$ states and metallic, strongly incoherent (non-Fermi-liquid) Ni $x^2-y^2$ ones. Our analysis of magnetic correlations suggests the formation of intertwined spin and charge density wave stripes in the bilayer ${\mathrm{NiO}}_6$ slab, in close similarity to the double-layer material. We identify two major instabilities: a leading one associated with a propagating wave vector $\mathbf{Q}=(\frac{1}{3},\frac{1}{3})$ (associated, e.g., with an “up-down-0” spin pattern or “$d^8–d^8–d^8\underline{L}$” charge-density wave with Ni $d^8\underline{L}$ ions bonded in an interlayer spin polaron), competing with the bicollinear $(\frac{1}{4},\frac{1}{4})$ (“up-up-down-down”) stripe state. In contrast, the single-layer Ni $3d$ electrons exhibit an instability toward the Néel-type magnetic state. Under pressure, 1212-LNO undergoes an orbital-selective Mott insulator-to-metal phase transition, associated with metallization of the single-layer Ni $e_g$ states. As a result, the single-layer Ni $e_g$ bands exhibit non-Fermi-liquid (bad metal) behavior with strongly incoherent spectral weights near the Fermi level. We note that correlation effects result in a remarkable reconstruction of the symmetry and strength of magnetic correlations as compared to those obtained within DFT. In fact, we observe a crossover from single-layer (as obtained within DFT) to double-layer-dominated magnetic correlations.

Two-dimensional materials have enabled unprecedented control over material properties through interlayer engineering, where mechanisms such as sliding can directly modify symmetry configurations and functionalities. Based on first-principles calculations, we demonstrate that bilayer $\mathrm{VP}{X}_3$ $(X=\mathrm{S},\mathrm{Se},\mathrm{Te})$ provides an ideal platform in which interlayer sliding simultaneously activates and couples sliding ferroelectricity (FE) and altermagnetism (AM). Here, a switchable out-of-plane FE polarization emerges from the sliding-induced breaking of inversion symmetry, whereas momentum-dependent spin splitting arises from crystal symmetries, without spin-orbit coupling. Crucially, the interlayer sliding displacement that reverses FE polarization also fully inverts the spin polarization in the AMs, equivalent to a 180° spin reversal. Remarkably, this magnetoelectric (ME) coupling is directly manifested as clear sign reversals in the magneto-optical Kerr rotation. Furthermore, interlayer compression enhances both the FE polarization and AM band splitting in a nearly linear manner, demonstrating strain-tunable multiferroic behavior. Our results establish $\mathrm{VP}{X}_3$ bilayers as a prototypical system for achieving deterministic control over coupled ferroic orders via atomic-scale layer manipulation, opening avenues for designing spintronic and ME devices.

Discrete charge fluctuations, routinely observed in semiconductor quantum dot devices, may contribute significantly to device drift and errors resulting from qubit miscalibration. Understanding the nature and origins of these discrete charge fluctuations may provide insights into material improvements or means of mitigating charge noise in semiconductor quantum dot devices. In this work, we measure multilevel charge fluctuations present in a Si/SiGe double quantum dot device over a range of device operating voltages and temperatures. To characterize the parameter-dependent dynamics of the underlying fluctuating degrees of freedom, we perform a detailed analysis of the measured noise time series. We perform algorithmically assisted drift detection and change point detection to detrend the data and remove a slow fluctuator component, as a preprocessing step. We perform model comparison on the postprocessed time series between different $n$-level fluctuator ($n\mathrm{LF}$) factorial hidden Markov models, finding that, although at most sweep values the independent pair-of-2LFs model would be preferred, in a particular region of voltage space, the 4LF model outperforms the other models, indicating a conditional rate dependence between the two fluctuators. By tracking fluctuator transition rates, biases, and weights over a range of different device configurations, we estimate gate voltage and conductivity sensitivity. We fit a phenomenological, detailed balance model to the extracted independent 2LF rate data, yielding lever arm estimates in the range of $-2–4\mu \mathrm{eV}/\mathrm{mV}$ between the two 2LFs and nearby gate electrodes. We expect that these characterization results may aid in subsequent spatial triangulation of the charge fluctuators.

Measurements of resistive breakdown in electronic systems under a DC electric field have shown that the threshold fields for the insulator-to-metal transition are significantly lower than predicted by single-electron excitation scenarios, such as the Landau-Zener theory. In this work, we propose an alternate mechanism of destabilizing ordered insulators under a DC electric field by fluctuations of the order parameters through the Goldstone mode excitations. The low-energy bosonic excitations receive energy from accelerated electrons and thus destroy the spontaneous symmetry breaking. Using the Keldysh Green's function formalism, we numerically confirm that the Goldstone mode remains well-defined in the nonequilibrium steady state, while its nonequilibrium excitations are sensitive to the electric field. The effective temperature of the Goldstone mode increases much more rapidly than the electronic effective temperature, with the bosonic threshold field significantly smaller than the electronic one, which suggests that collective phase dynamics may further reduce the transition field to the experimental range via a purely electronic mechanism.

Determining the Fermi surface (FS) volume in underdoped cuprates is crucial for understanding the nature of the strongly correlated pseudogap phase. Conventional quantum oscillation techniques, typically used for this purpose, are inapplicable in this high-temperature regime due to thermal and disorder-induced smearing of Landau levels. We propose Sondheimer oscillations (SO), semiclassical oscillations of in-plane magnetoresistivity in thin films, as a robust alternative probe of FS reconstruction. SO arise from the commensuration between the cyclotron radius and film thickness, do not rely on Landau quantization, and remain observable at moderate fields and elevated temperatures where quantum oscillations are suppressed. Their frequencies depend solely on the FS parameters (e.g., curvature), and not on specific details of scattering mechanisms. SO are also sensitive to the coherence of interlayer tunneling, allow contributions from individual FS pockets to be distinguished in the frequency domain, and naturally include the Yamaji angle effect (if present in the system) as a prominent feature in the frequency spectrum. We compute SO spectra as a function of the magnetic field orientation for three representative scenarios: (i) an unreconstructed large FS, (ii) a spin density wave reconstructed FS with volume $p/4$, and (iii) a fractionalized Fermi liquid (${\mathrm{FL}}^{*}$) with pocket volume $p/8$ (here $p$ is the hole doping). We show that the SO spectrum offers a wealth of universal features that could be used to differentiate between these scenarios. In particular, we highlight a FS geometry-dependent phase shift between oscillations in longitudinal and transverse conductivities, characterize how the FS curvature can be extracted from SO if the film orientation is perpendicular to the crystallographic $c$ axis, and analyze the evolution of the SO spectrum with doping.

Femtosecond time-resolved optical absorption spectroscopy of gallium arsenide was performed using an x-ray free-electron laser (XFEL) to excite the K-shell electrons. The transient absorption spectra show a distinct increase in absorption extending to approximately $50\mathrm{meV}$ below the band gap within $1.4\mathrm{ps}$ after XFEL irradiation, suggesting the formation of localized states associated with core-hole generation. The transient feature subsequently relaxes on a few-picosecond timescale through many-body processes, accompanied by Pauli blocking arising from the redistribution of hot carriers within the valence and conduction bands. By comparison with near-infrared laser excitation, we found that x-ray excitation is characterized by the formation of transient absorption states below the band gap and reduced carrier accumulation at the conduction-band minimum. These results provide valuable insights into x-ray-induced electronic structure modifications and carrier dynamics in semiconductors on the picosecond timescale, where deep core holes and many-body effects play crucial roles.

We study the formation of hybrid plasmon–magnon modes in a heterostructure comprising a monolayer semiconductor with strong Rashba spin–orbit coupling—specifically, Janus transition-metal dichalcogenides (TMDs)—and an insulating ferrimagnet, such as yttrium iron garnet-based compounds. Using a combined microscopic-macroscopic framework for plasmon–magnon coupling, we show that plasmons and magnons strongly hybridize over both GHz and THz frequency ranges, enabling experimental access well above cryogenic temperatures. Moreover, the developed approach provides an efficient and natural classification of the topology of the hybrid modes, rooted in the phase winding of the plasmon–magnon coupling induced by spin–momentum locking and the associated chiral winding of the electronic spin along the Fermi contours. Finally, we identify experimentally accessible manifestations of the hybridization, such as topological interface modes and an anomalous thermal Hall response.

We propose extended $s$-wave altermagnets ($s\mathrm{AMs}$) as a class of magnetic states that are fully gapped, spin compensated, and feature spin-polarized bands. $s\mathrm{AMs}$ are formed through valley-exchange symmetries, which act as momentum-space translations beyond standard crystallographic spin-group classifications. Using an effective two-valley model, we demonstrate that $s\mathrm{AMs}$ exhibit isotropic spin splitting, enable spin-selective transport in tailored heterostructures, and give rise to descendant pair density wave order. From a microscopic $s\mathrm{AM}$ minimal model, we develop the guiding principles to identify $s\mathrm{AMs}$ in quantum magnets.

Fluctuations in disordered matter play a central role in determining material properties and physical responses. Recent studies have identified an exotic class of systems known as structurally hyperuniform materials, in which large-scale density fluctuations are anomalously suppressed through special spatial organization of particles, phases, or microstructural features. Here we demonstrate that ordinary, structurally nonhyperuniform disordered materials can nevertheless support hyperuniform physical source fields, including scalar, vector, or tensor observables such as incompatibility, bound charge, and bound current. These sources can also regularize the response fields they drive. We develop a general theoretical framework in which a physical field is generated from a more primitive parent field through a local physical operator. In Fourier space, the spectrum of the derived field is determined by the product of the parent-field spectrum and the Fourier symbol of the operator. When the operator has a small-wave-number zero of order $m$, the derived source spectrum is suppressed by $k^{2m}$ relative to the parent spectrum in the coupled spectral channels. For a parent spectrum scaling as $k^{\alpha }$, hyperuniformity is guaranteed if $\alpha +2m>0$, provided the assumed infrared scaling holds; sufficiently infrared-divergent parent fluctuations need not yield a hyperuniform source. We demonstrate this mechanism in elastic, electrostatic, and magnetostatic settings, showing that operator-generated incompatibility, bound charge, and bound-current fields can become hyperuniform even when their parent eigenstrain, polarization, or magnetization fields remain conventionally disordered. These findings identify a general, explicitly conditional route to field hyperuniformity through local physical constraints and distinguish hyperuniform source generation from regularization of the resulting response fields.

Using first-principles calculations, we investigate how homogeneous strain and crystallographic surface orientation modify the vibrational and superconducting properties of niobium. For bulk Nb, tensile strain strongly softens the phonon spectrum and enhances the electron-phonon coupling, increasing the superconducting transition temperature within the harmonic approximation from 9.5 K at equilibrium to 14.6 K at $\sim 6\%$ lattice expansion. Anharmonic corrections are small near equilibrium but become increasingly significant under tensile strain and considerably reduce this enhancement at large expansion. For ultrathin Nb slabs with low-index (001), (110), and (111) surface orientations, harmonic phonon calculations exhibit imaginary modes, showing that anharmonic lattice effects are essential. To treat these effects efficiently, we train Nb-specific machine-learning interatomic potentials on bulk and slab first-principles configurations and use them to accelerate stochastic self-consistent harmonic approximation calculations, thereby obtaining anharmonically renormalized phonon modes that are combined with density-functional perturbation theory electron–phonon matrix elements to construct the Eliashberg spectral function. Among the three clean free-standing slabs examined, Nb(001) exhibits the strongest electron-phonon coupling and the highest calculated transition temperature of 10.1 K, while Nb(110) and Nb(111) show progressively reduced pairing strength. Finally, by analyzing the Eliashberg spectral function and the functional derivative $\delta T_{\text{c}}/\delta {\alpha }^{2}F\left(\omega \right)$, we identify the phonon energy ranges most effective for superconducting pairing. Our results show that strain, surface termination, and anharmonic phonon renormalization provide complementary and interrelated microscopic routes for tuning superconductivity in Nb.

We construct a generalized time-dependent Ginzburg-Landau model to demonstrate the possibility of inducing $p$- and $d$-wave components in an originally pure $s$-wave centrosymmetric superconductor via microwave radiation. In this framework, specializing to $O_h$ point-group symmetry, we introduce gradient terms that couple the $s$-wave superconducting order parameter with other symmetry-allowed components. The singlet-to-singlet gradient terms are quadratic in spatial derivatives, while, in the presence of spin-orbit coupling, linear-in-derivatives terms coupling singlet and triplet order parameters are also permitted. Through the minimal substitution procedure, these terms enable coupling between different superconducting order parameters via the vector potential, thereby leading to the generation of $p$-wave, $d$-wave, and other symmetry-allowed components. Such a manipulation of the superconducting state locally via a microwave beam could be considered as one more facet of the concept of quantum printing.

Hafnia-based ferroelectric films switch at room-temperature coercive fields of about $1\mathrm{MV}{\mathrm{cm}}^{-1}$, an order of magnitude below the fields predicted for homogeneous polarization reversal. The predicted switching fields can exceed the dielectric breakdown strength, although polarization reversal is experimentally observed before breakdown. In this work, we use first-principles calculations and symmetry-reduced atom mappings to compare switching in the polar $Pca{2}_1$ and $Pmn{2}_1$ structures of ${\mathrm{HfO}}_2$ and ${\mathrm{Hf}}_{0.5}{\mathrm{Zr}}_{0.5}{\mathrm{O}}_2$ (HZO). Systematic comparison of the matched pathways shows that Zr substitution lowers nearly all sampled $Pca{2}_1$ barriers and produces a particularly low-barrier $Pmn{2}_1 {180}^{\circ }$ reversal route. The comparison identifies a favorable $Pmn{2}_1 {180}^{\circ }$ reversal whose barrier is substantially reduced in HZO. For a field normal to the predominantly exposed $\left\{111\right\}$ facets, the estimated room-temperature critical field for this route, obtained using phenomenological fourth-order Landau-Ginzburg-Devonshire temperature scaling, decreases from 2.57 $\mathrm{MV}{\mathrm{cm}}^{-1}$ in ${\mathrm{HfO}}_2$ to 1.02 $\mathrm{MV}{\mathrm{cm}}^{-1}$ in HZO. These results clarify how Zr substitution lowers the switching field. The identified reversal pathway helps explain the discrepancy between conventional homogeneous-switching predictions and low-field measurements.

We investigate the emergence of a scarred discrete time crystal (SDTC) phase in a periodically driven dimerized spin chain. While generic interacting Floquet systems are expected to thermalize according to the eigenstate thermalization hypothesis (ETH), we demonstrate that this system hosts quantum many-body scars (QMBS) that induce a regime of weak ergodicity breaking. Through an analysis of Floquet level statistics, entanglement entropy, and eigenstate fidelity, we identify a manifold of low-entanglement states characterized by semi-Poisson statistics embedded within an otherwise thermal spectrum. These scarred states support robust subharmonic oscillations with period doubling, signaling the spontaneous breaking of discrete time-translation symmetry. We show that the SDTC response is robust against a variety of initial state configurations, demonstrating its stability beyond fine-tuned conditions. A finite-size scaling analysis reveals that the time-crystalline lifetime grows with system size within the range accessible to our exact-diagonalization calculations. However, drawing on the general phenomenology of approximate many-body scars, we expect that hybridization between Floquet scars and the thermal continuum will eventually curtail this growth, causing the lifetime to saturate at system sizes beyond our current numerical reach. This characterizes the SDTC as a long-lived metastable dynamical regime rather than a strictly stable thermodynamic phase, providing a comprehensive framework for understanding the interplay between periodic driving and constrained many-body dynamics in disorder-free systems.

Two-dimensional (2D) multiferroics offer an appealing platform for electrically and magnetically reconfigurable nonlinear photoresponses. In particular, the bulk photovoltaic (BPV) effect, as a second-order nonlinear optical response rooted in Bloch wave quantum geometry, is highly sensitive to crystalline and magnetic symmetries. Therefore, the BPV effect could serve as a sensitive method to capture subtle symmetries in multiferroic systems with fruitful ferroic order switching. Here, taking a monolayer multiferroic $\mathrm{CuCr}{\mathrm{P}}_2{\mathrm{S}}_6$ as a representative example, we systematically investigate the BPV effect across the paraelectric-ferroelectric-antiferroelectric phase transition by combining first-principles calculations with magnetic group symmetry analysis. We explore the influence of phase transition, polarization reversal, multiferroicity, magnetic order, magnetocrystalline anisotropy, and its emergent altermagnetism on the BPV responses. Our results suggest that the BPV effect can effectively distinguish distinct polarization and magnetic states, establishing monolayer $\mathrm{CuCr}{\mathrm{P}}_2{\mathrm{S}}_6$ as a promising 2D multiferroic platform for electrically and magnetically reconfigurable BPV and nonlinear optoelectronic devices.

We report on current-induced spin–orbit torques and field-free magnetization switching in a two-dimensional van der Waals heterostructure consisting of ${\text{WTe}}_2$ as the spin source and ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ as the magnetic layer. Harmonic magneto-optical Kerr effect measurements enable the disentanglement of torque components arising from out-of-plane and in-plane spin accumulations generated by charge transport in ${\text{WTe}}_2$. Our analysis reveals a dominant contribution from out-of-plane spins, yielding a field-like torque efficiency of approximately $8.8\%$, and a damping-like torque efficiency arising from in-plane spins of $1.8\%$ at $150\mathrm{K}$. We observe deterministic bipolar field-free switching of the perpendicular magnetization of ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ up to the Curie temperature, consistent with the strong torque generated by out-of-plane spins. The switching efficiencies extracted from current-induced magnetization reversal and hysteresis loop shifts exceed the intrinsic torque efficiencies measured by harmonic magneto-optical Kerr effect by more than one order of magnitude. The switching efficiencies scale with the temperature-dependent coercivity of the ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ flake, indicating that they reflect a combination of thermal effects assisting magnetization reversal and different torque components. Our results provide a quantitative assessment of unconventional spin–orbit torques in ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2/{\text{WTe}}_2$ and emphasize the importance of carefully interpreting torque efficiencies derived from switching-based measurements, particularly in van der Waals systems with Curie temperatures near or below room temperature.