Borophene, an outstanding platform to elucidate the structure-property relationship, possesses diverse concentration and spatial arrangement of hexagonal vacancies (HVs) owing to its structural polymorphism. Here, we study electron transport in disordered borophene nanoribbons (BNRs) with two types of HVs distributed randomly on a triangular lattice, namely, unrestricted HVs and restricted ones. Unrestricted HVs which distribute stochastically at all spatially allowed sites function as strong scatterers and lead to Anderson localization over the entire energy spectrum. In contrast, confining HVs to predefined sites separated by a fixed distance preserves quantized conductance peaks associated with resonant tunneling, although the overall transmission ability is reduced. The magnitude of these quantized resonant peaks is robust against the HV probability, nanoribbon length, disorder configuration, and inhomogeneous model parameters, while their position and number are tunable via the fixed distance and nanoribbon width. Remarkably, the transmission ability around resonant energies could be enhanced by the HV probability, revealing a counterintuitive regime of HV-enhanced electron transport. The underlying physics can be understood from local current distributions and wave-function analysis, indicating the emergence of distinct transmission modes arising from specific arrangement of HVs. In particular, we reveal a resonant mechanism mediated by extended states whose amplitudes strictly vanish at predefined HV sites, rendering electronic transport entirely unaffected by defect scattering. These results establish HV engineering as an alternative route to manipulate quantum transport in disordered BNRs, with potential relevance to other triangular lattices, such as transition-metal dichalcogenides and moiré materials.

We systematically investigate the entanglement and information dynamics of quasiperiodic systems across their extended, critical, and localized phases, aiming to identify dynamical signatures that can reveal the multifractal spatial structure of critical states and distinguish critical phases from the extended and localized regimes. Focusing on the generalized Aubry-André-Harper model, we complement the half-chain entanglement entropy with the spatially resolved subsystem information capacity (SIC) and demonstrate that critical states exhibit pronounced spatial heterogeneity absent in the extended and localized phases. In the steady state, the SIC reveals a stepwise ramp as a function of subsystem size, reflecting an underlying fragmentation of the chain into weakly connected subregions. Dynamically, information initially localized within such a subregion can undergo coherent long-lived oscillations, dubbed subregion echoes, whose period scales with the subregion length, in quantitative agreement with a quasiparticle picture of confined quasiparticle reflections. We trace this internal fragmentation to the incommensurately distributed zeros (IDZs) in the off-diagonal hopping terms of the Hamiltonian. To establish the generality of the SIC as a diagnostic tool, we further apply it to a mobility-edge phase with coexisting extended and localized states and to a critical phase that does not originate from IDZ fragmentation, and show that the SIC can cleanly distinguish these scenarios through their distinct steady-state profiles, initial-site sensitivities, and the presence or absence of subregion echoes. Our results demonstrate that the SIC serves as a powerful real-space probe for diagnosing critical phases and uncovering the bottlenecked connectivity that underlies the multifractal structure of critical states.

Non-Hermitian systems exhibit a fundamental spectral dichotomy absent in Hermitian physics: the eigenvalue spectrum and the eigenstate spectrum can deviate significantly in the thermodynamic limit. We explain how extrapolating finite-size eigenvalues can miss important asymptotic eigenstates, with the unidirectional Hatano-Nelson model serving as a minimal realization of this phenomenon. Through exact analytical solutions, we show that this model contains not only hidden asymptotic modes but also quasi-Jordan structures that become macroscopic in the thermodynamic limit and appear more generally in systems with nontrivial bulk winding. Our framework explains how the apparent failure of the bulk-edge correspondence in models such as the non-Hermitian Su-Schrieffer-Heeger (SSH) chain can reflect the failure of finite-size eigenvalue extrapolation to detect asymptotic edge states in systems with a skin effect. These results clarify the limitations of using finite-size eigenvalues alone to infer thermodynamic-limit topology.

Spin-orbit torque (SOT), which enables electrical control of magnetization, plays a crucial role in the development of next-generation spintronic devices. Realizing SOT in two-dimensional van der Waals systems, together with achieving efficient nonvolatile manipulation via ferroelectricity, would be highly beneficial for the implementation of tunable logic devices with enhanced storage density. In this work, based on first-principles calculation and using a multiferroic ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2/{\mathrm{In}}_2{\mathrm{Se}}_3$ heterostructure as a representative example, we demonstrate that switching the ferroelectric polarization of the ${\mathrm{In}}_2{\mathrm{Se}}_3$ layer induces a pronounced modification in the magnetization-dependent distribution of torkance within the heterostructure. Specifically, when the magnetization is along the in-plane direction, where the torque is maximal, reversing the polarization of ${\mathrm{In}}_2{\mathrm{Se}}_3$ from upward to downward enhances the total torkance to more than 150% of its original value. This substantial variation primarily originates from the polarization-induced modulation of the $z$ component of the time-reversal-odd torkance, which is mainly associated with an approximately 233% change in the atomic-resolved torque contributed from the middle Fe layer in ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ layers. Further analysis reveals that the electronic states near $\mathrm{\Gamma }$ on the Fermi surface undergo significant reconstruction upon polarization switching, which is responsible for the observed variation in the time-reversal-odd torque. Our results not only provide unique insights into the functional potential of van der Waals multiferroic heterostructures but also offer a viable strategy for achieving electrically tunable SOT, paving the way for future programmable spintronic devices.

We demonstrate the stray-field-mediated skyrmion stabilizing capabilities of ultrathin exchange-decoupled antisymmetric ferromagnetic bilayers based on conventional transition metal materials. Using an asymptotically exact micromagnetic model valid in the ultrathin film limit, we show that the antisymmetric tailoring of the bilayer allows the Dzyaloshinskii-Moriya interaction and the dipolar interaction to act synergistically to stabilize skyrmions, in contrast to the monolayer case, in which these energies compete. To obtain optimal stability of these skyrmions against collapse and bursting—the two fundamental processes determining skyrmion lifetime, we carry out an asymptotic analysis of the saddle point solution that separates the skyrmion from the demagnetized state. The result is an optimal stability line for compact skyrmions in the nondimensional parameter space of the effective Dzyaloshinskii-Moriya interaction strength and the effective film thickness. Our predictions are confirmed by extensive micromagnetic simulations of antisymmetric bilayers, using magnetic parameters of the conventional $\mathrm{Pt}/\mathrm{Co}/{\mathrm{AlO}}_x$ systems. Our results may provide a new pathway for experimental observations of 10-nm-radius zero-field skyrmions with lifetimes compatible with information technology applications.

When two ferromagnetic thin films with different magnetic easy axes are coupled via the exchange interaction, the magnetization process becomes nontrivial. In this paper, we demonstrate that three-dimensional magnetization information in such a bilayer system can be accessed electrically by combining measurements of the anomalous Hall effect (AHE) and anomalous Nernst effect (ANE). Specifically, we investigate a ${\mathrm{CoFe}}_2{\mathrm{O}}_4$(001)/Fe bilayer, where the insulating nature of ${\mathrm{CoFe}}_2{\mathrm{O}}_4$ ensures that these transport measurements selectively probe only the conductive Fe layer. By combining the AHE and ANE results and comparing them with a simple micromagnetic simulation, we probe the magnetic configuration of the antiferromagnetically coupled Fe layer and suggest the emergence of a twisted magnetic structure near the interface.

We report the magnetic and transport properties of single-crystalline ${\mathrm{Ce}}_4{\mathrm{Ge}}_7$, which crystallizes in a noncentrosymmetric orthorhombic structure (space group $C{222}_1$ ). It undergoes an antiferromagnetic transition at $T_{\mathrm{N}}=7.3\mathrm{K}$. When a magnetic field is applied along the $b$ axis, a metamagnetic transition occurs at 1.3 T (at 2 K) and vanishes above $T_{\mathrm{N}}$. Correspondingly, this transition gives rise to an anomalous Hall effect, which is dominated by the intrinsic Karplus-Luttinger mechanism. Under hydrostatic pressure, $T_{\mathrm{N}}$ of ${\mathrm{Ce}}_4{\mathrm{Ge}}_7$ initially increases slightly and is then gradually suppressed. For pressures above $P_{\mathrm{c}}=10.2\mathrm{GPa}$, no magnetic order is observed. The divergence of the $A$ coefficient, the maximum of the residual resistivity, and the non-Fermi liquid behavior around $P_{\mathrm{c}}$ indicate the possible existence of an antiferromagnetic quantum critical point in ${\mathrm{Ce}}_4{\mathrm{Ge}}_7$.

We develop a theoretical framework for planar quasiballistic Josephson junctions, where multiple superconducting leads are coupled through a large, nearly ballistic normal metal crystal. Our approach, based on quasiclassical Eilenberger equations, accounts for the dominant role of electron reflections from the crystal surfaces or single impurities, a mechanism distinct from both purely ballistic and diffusive limits. We calculate the critical current between superconducting leads for various geometries, examining its dependence on temperature and magnetic field. Crucially, we demonstrate that in multiterminal setups, the junctions are not independent but form a strongly coupled system. The theory successfully explains key experimental observations from a companion work [Polevoy et al., Phys. Rev. Lett. 137, 166001 (2026)], including a nonmonotonic dependence of the critical current on the interlayer length, providing a foundation for designing and understanding complex multiterminal Josephson systems.

We investigate the effect of the non-Hermitian Gamma interaction on the phase transitions and magnetic correlations in the transverse field Ising chain. We demonstrate that apart from the gapped antiferromagnetic and paramagnetic phases, there is a gapless phase induced by parity-time symmetry breaking, where the system exhibits long-range and short-range spin-nematic correlations in different regions, divided by the quantum critical line determined from the correlation function and the subsystem entanglement entropy. Furthermore, we reveal that the parity-time symmetry breaking leads to the emergence of dynamical spin-nematic correlation, which also provides a way of characterizing the spin-nematic map through nonequilibrium dynamics. Our findings show that rich quantum phases stem from the competition among the Ising interaction, transverse field, and non-Hermitian Gamma interaction, and provide a scheme for generating spin-nematic correlation in the spin chain.

Boundary time crystals (BTCs) are paradigmatic examples of continuous time crystals that emerge in collective, dissipative quantum systems. Their microscopic origin, however, remains obscured by the complexity of Lindbladian many-body dynamics and has largely been investigated through semiclassical and numerical approaches. Here, we develop an exact operator space framework for collective spin Lindbladians based on irreducible tensor representations. We map the Lindbladian dynamics onto a local non-Hermitian hopping problem, where weak symmetries impose selection rules on operator transport, while the hopping amplitudes and their relative strengths determine the resulting dynamical regimes. We identify the microscopic ingredients that distinguish models supporting conventional collective precession from those supporting BTC dynamics. Our approach further reveals how nonunital dissipation can provide a source for the traceless operator subspace, revealing a microscopic mechanism for the reduced sensitivity of BTC dynamics to initial conditions beyond mean-field descriptions. More broadly, our results establish operator space transport as a general perspective for understanding dissipative many-body dynamics and its connections to non-Hermitian phenomena.

The low-temperature thermodynamic properties and magnetic structure of the garnet oxide ${\mathrm{Mn}}_3{\mathrm{V}}_2{\mathrm{Ge}}_3{\mathrm{O}}_{12}$ (MVGO) have been investigated via magnetic susceptibility, specific heat, and neutron diffraction measurements. MVGO exhibits two successive magnetic transitions at $T_{\mathrm{N}1}=4\mathrm{K}$ and $T_{\mathrm{N}2}=2.6\mathrm{K}$, associated with the antiferromagnetic ordering of noncollinear ${\mathrm{Mn}}^{2+}$ and collinear ${\mathrm{V}}^{3+}$ sublattices, respectively. The Curie-Weiss analysis based on the susceptibility data and the magnetic entropy derived from the specific heat measurement confirmed the ground state $S=5/2$ for ${\mathrm{Mn}}^{2+}$ and $S=1$ for ${\mathrm{V}}^{3+}$. Density functional theory calculations reproduce the experimentally determined magnetic structures, yielding nearest-neighbor antiferromagnetic couplings $J_{\text{Mn-Mn}}$ and $J_{\text{V-V}}$ along with a ferromagnetic coupling $J_{\text{Mn-V}}$. By applying a magnetic field, we construct a temperature-field phase diagram for MVGO that encompasses multiple distinct phases. These results establish MVGO as a complex system among garnet-structure magnets.

Alternating (AC) magnetic fields can induce not only an alternating magnetization in materials, but also an alternating temperature via the magnetocaloric effect. The latter effect is typically neglected when performing AC susceptibility measurements, but consideration of both effects on an equal footing is necessary in order to reliably distinguish between internal and external causes of magnetic response and accurately extract quantitative information about relaxation processes. In order to address this, we have developed a method to measure the AC magnetocaloric effect that is compatible with AC susceptibility measurements, and also a framework to analyze these data in combination. We demonstrate the efficacy of this approach using ${\mathrm{YbVO}}_4$, a material for which strong single-ion anisotropy leads to slow electronic spin-lattice relaxation at low temperatures via a phonon bottleneck effect. We report AC magnetic susceptibility and AC magnetocaloric effect measurements for this material as a function of field and frequency at a temperature of 3 K. We analyze the data using a discretized thermal model, and extract the field dependence of the intrinsic spin-lattice relaxation rate. This demonstration experiment illustrates a general approach to quantitatively address multiple measured quantities in driven systems using a unified thermal circuit analysis. The thermal analysis methods presented in this report can be extended to study other magnetic, dielectric, and elastic materials exhibiting a complex response to an external driving field in the presence of internal and external relaxation, particularly when an energy dissipation process is within an accessible frequency regime.

An effective dynamical equation for the magnetization of a nanomagnet with surface anisotropy is derived from an atomistic spin Hamiltonian using the spin coherent-state path integral formalism. The derivation proceeds in two steps. First, the continuum Euclidean action for the many-spin nanomagnet is obtained, including the Wess-Zumino-Witten (Berry phase) term, as well as exchange, Zeeman, and core/surface anisotropy contributions. Second, the local magnetization density is decomposed into a slowly varying macrospin component and transverse spin-misalignment fluctuations driven by surface effects. A systematic expansion of the action is then performed up to quadratic order in the transverse-fluctuation variables. Under the adiabatic approximation, where transverse modes relax much faster than the macrospin, these modes are eliminated using their static Green's-function solution. This results in a closed, extended Landau-Lifshitz equation for the macrospin, featuring an effective field with nontrivial corrections from spin misalignment. These corrections renormalize both the Zeeman and anisotropy fields and introduce additional terms that act as nutation- and damping-like contributions. For a spherical nanoparticle with Néel surface anisotropy, the leading surface-induced correction is explicitly evaluated, and its structure is compared to inertial extensions of the Landau-Lifshitz-Gilbert equation. Together, these results establish a microscopic foundation for surface-induced magnetization nutation in nanomagnets and provide a framework to estimate corrections to the precession frequency and effective damping. The corresponding shift in the ferromagnetic-resonance frequency and linewidth is measurable with standard GHz spectrometers, and the underlying adiabatic-elimination mechanism is expected to generalize to any slow magnetic variable coupled to a bath of fast fluctuating modes.

Altermagnetism features strong momentum-dependent spin splitting despite zero net magnetization, offering a transformative platform for next-generation spintronics. However, the nonvolatile and deterministic switching between its two equivalent spin-splitting states remains a fundamental bottleneck. Here, we propose a universal layer-engineering paradigm to achieve symmetry-enforced ferroelectric switching of two-dimensional altermagnetism. By sandwiching a conventional antiferromagnetic monolayer between two identical ferroelectric layers, the out-of-plane polarization cleanly breaks the spatial symmetry to induce robust altermagnetic splitting. Crucially, the global combined parity-time symmetry dictates that reversing the ferroelectric polarization exactly inverts the altermagnetic spin-splitting pattern. We rigorously validate this mechanism in the ${\mathrm{In}}_2{\mathrm{Se}}_3/{\mathrm{MnPTe}}_3/{\mathrm{In}}_2{\mathrm{Se}}_3$ trilayer using first-principles calculations. As a direct consequence, the ferroelectrically driven spin-splitting reversal deterministically flips the anomalous Hall effect signal, providing an unambiguous transport fingerprint to electrically distinguish the two altermagnetic states. Unconstrained by the stringent symmetry requirements of intrinsic single-phase materials, our findings establish a versatile physical framework for electrically addressable altermagnetic spintronics.

The electronic and optical properties of quasi-one-dimensional transition-metal trichalcogenides remain largely unexplored beyond the mean-field approximation, and it is not clear how they evolve as the crystal is thinned. By performing first-principles many-body perturbation theory calculations, we determine the quasiparticle band structures and the polarization-resolved optical response of ${\mathrm{ZrS}}_3$ in the bulk, bilayer, and monolayer limits, using a hierarchy of methods (hybrid DFT, $GW$, and the Bethe-Salpeter equation). We find that all three systems are indirect-gap semiconductors with a quasidirect character, the direct-indirect splitting being $\delta \approx 0.10–0.13\mathrm{eV}$ and nearly independent of both the level of theory and the dimensionality. The mean-field gaps are almost insensitive to thickness, whereas the quasiparticle corrections increase the gap by $\approx 0.9\mathrm{eV}$ from bulk to monolayer. The effective exact-exchange fraction reproducing the $GW$ gap scales as $\alpha \sim {\varepsilon }_{\infty }^{-1}$, increasing from $\approx 0.19$ to $\approx 0.33$, so that no single hybrid functional describes the full dimensional series. The optical onset blueshifts monotonically ($\approx 2.4\to 2.8\to 3.0\mathrm{eV}$) and the near-edge absorption is strongly dichroic. A change in light polarization does not simply shift the excitonic resonance ($\approx 0.09\mathrm{eV}$); it also reorganizes the underlying excitonic wave function, selecting distinct band channels and $\mathbf{k}$-space regions. A real-space, participation-ratio analysis resolves moderately delocalized, Wannier-Mott-like excitons templated along the covalent chains. They are predominantly sulfur-derived (75%–88% of the density on sulfur for the chain-polarized bulk states), which identifies them as (${\mathrm{S}}_2{)}^{2-}$ disulfide excitations rather than $\mathrm{S}\to \text{Zr}$ charge-transfer states, while in the bilayer the electron delocalizes across both layers, the real-space imprint of interlayer screening. These results provide a consistent reference for the quasiparticle and excitonic energy scales of ${\mathrm{ZrS}}_3$ from the bulk to the few-layer limit.

Orbital-free density functional theory (OFDFT) has reemerged as a viable alternative to Kohn-Sham DFT, driven by recent advances in kinetic energy density functionals (KEDFs). Nonlocal KEDFs have significantly extended OFDFT's applicability, particularly for bulk solids, but their high computational cost and dependence on system-specific parameters limit their universality. In this work, we propose a semilocal KEDF at the generalized gradient approximation level that achieves accuracy comparable to the state-of-the-art semilocal functionals while remaining parameter-free. Our construction revives the Thomas-Fermi–von Weizsäcker (TFvW) framework by modulating the relative contributions of TF and vW terms through physically motivated constraints and preserving the exact second-order gradient expansion. Despite its simple form, the proposed functional (KGE2) performs well across both extended systems (metals and semiconductors) and finite systems (clusters), without any need for empirical tuning. These results mark a step toward the development of transferable and computationally efficient semilocal KEDFs for large-scale OFDFT simulations.

We present a comprehensive first-principles investigation of all symmetrically inequivalent low-index surfaces of $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$, examining their structural properties and thermodynamic stability across experimentally relevant growth conditions. Using density-functional theory with both the semi-local functional PBEsol and a modified PBE0 hybrid functional with $26\%$ exact exchange, denoted PBE0(0.26), we calculate surface free energies for the (010), (100), (001), ($\overline{2}01$), (110), (111), and ($11\overline{1}$) orientations, including the effects of harmonic vibrational contributions and varying oxygen chemical potentials. We demonstrate that the energetic ordering remains consistent across computational approaches and that the vibrational contributions remain below $0.2\mathrm{J}/{\mathrm{m}}^2$ up to temperatures of $1000\mathrm{K}$. A coordination-based model that correlates surface stability with the density of undercoordinated atoms reveals that undercoordinated oxygen atoms and tetrahedral Ga sites substantially destabilize surfaces, while exposed undercoordinated octahedral Ga atoms serve as indicators of surface stability. Our thermodynamic analysis shows that stoichiometric terminations dominate over nearly the entire range of chemical potentials relevant for $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ stability, while nonstoichiometric terminations emerge only under extreme reducing or oxidizing conditions. Notably, we predict the formation of stable Ga-rich terminations resembling Ga adlayers for the (100) and ($\overline{2}01$) surfaces under highly reducing conditions.

Quantum dot-cavity hybrid systems enable statistics-dependent energy storage in circuit quantum electrodynamics, yet the energy transfer mechanism to an acceptor remains unresolved. Here, we theoretically demonstrate controlled energy release from a voltage-driven donor double quantum dot through a microwave cavity to an acceptor double quantum dot. For fixed cavity-acceptor coupling, when the cavity is prepared in a lasing state, it yields a significant photon population, enhancing the energy transfer to the acceptor. When this population is fixed, a larger cavity-acceptor coupling can further enhance the energy transfer. An increase in joint donor-cavity-acceptor coupling activates virtual-photon-mediated donor-acceptor interactions, which bypass the cavity decay channel and thereby facilitate the energy transfer. Crucially, engineering the acceptor with level spacing larger than the cavity energy enables multiphoton processes that redirect photons to electronic excitations with near-perfect selectivity, suppressing dissipation and boosting energy utilization. Our results provide a blueprint for efficient energy transfer in nanoscale photoelectric devices.