We study intrinsic thermal transport and Floquet-engineered topology in a two-dimensional $d$-wave altermagnetic topological insulator powered by linearly polarized light. We analyze the anomalous Hall, Nernst, and thermal Hall conductivities, as well as their spin-resolved equivalents, and develop closed-form formulas for the Berry curvature using an analytically calculated high-frequency effective Hamiltonian. We demonstrate that linearly polarized light, in contrast to conventional antiferromagnets, breaks the symmetry connecting spin sectors in altermagnets, allowing a series of spin-selective topological phase transitions from a quantum spin Hall state to a spin-polarized Chern insulator and finally to a trivial phase. The Nernst response shows substantial thermal activation and significant sensitivity to the gap size in the Chern domain, but both the electrical and thermal Hall responses become quantized and meet the anomalous Wiedemann-Franz law. Every anomalous transport coefficient exhibits a distinctive $d$-wave dependence on the polarization angle, reversing sign under orthogonal rotation and vanishing at symmetry-restoring directions. Our findings show a path to all-optical regulation of topological and caloritronic responses beyond traditional magnetic systems and establish thermal transport as a sensitive probe of altermagnetic order.

For the $t\text{−}J$ model, variational wave functions can generally be constructed based on an accurate description of antiferromagnetism (AFM) at half-filling and an exact phase-string sign structure under doping. The single-hole-doped and two-hole-doped states, as determined by variational Monte Carlo (VMC) simulations, display sharply contrasting behaviors. The single-hole state constitutes a “cat state” that resonates strongly between a quasiparticle component and a local loop-current component, with approximately equal weights. In the ground state, the quasiparticle spectral weight $Z_{\mathbf{k}}$ peaks at momenta ${\mathbf{k}}_0\equiv (\pm \frac{\pi }{2},\pm \frac{\pi }{2})$. The total-energy dispersion versus $\mathbf{k}$ agrees remarkably well with the Green function Monte Carlo results throughout the Brillouin zone. However, Landau's one-to-one correspondence hypothesis for quasiparticles breaks down here with the incoherent component exhibiting intrinsic magnetization originating from a minimal $2\times 2$ loop current that forms a $4\times 4$ pattern on the square lattice—a finding in excellent agreement with density matrix renormalization group (DMRG) calculations. In the two-hole ground state, a new pairing mechanism is revealed: the two holes are automatically fused into a tightly bound object consisting of an incoherent $d_{xy}$ pairing along the diagonal direction by compensating the local loop currents. This hole pair is again a “cat state” that resonates strongly between the incoherent $d_{xy}$ and a coherent $d_{x^2-y^2}$ Cooper channel to gain substantial hopping energy. Its size extends over an area of about $4\times 4$ lattice spacings, much smaller than the divergent AFM correlation length, implying that it should survive as a minimal superconducting building block even in the dilute doping regime. Experimental implications and the generalization to the finite-doping case are briefly addressed.

We study the linear optical conductivity of the ${\mathrm{Nb}}_{2n+1}{\mathrm{Si}}_n{\mathrm{Te}}_{4n+2}$ family of layered van der Waals materials, which has recently attracted considerable attention owing to its dimensionality-tunable electronic structure with a quasi-one-dimensional nodal-line state. At zero temperature, we analytically show that the Drude weight exhibits strong anisotropy: Along the transverse direction it is finite at charge neutrality, whereas in the nodal-line direction it vanishes quadratically with Fermi energy. On the other hand, the interband optical conductivity exhibits the same linear frequency dependence along both the longitudinal and transverse directions, with only a direction-dependent slope in the low-frequency regime. We further analyze the leading finite-temperature corrections to the intraband and interband optical conductivities, showing that the zero-temperature results remain valid up to experimentally relevant temperatures.

Berry curvature, as the imaginary component of quantum geometry, plays a crucial role in condensed matter physics. The spatial distribution of Berry curvature can be characterized by its dipole and multipole moments, which can induce the nonlinear anomalous Hall effect (NLAHE). To date, the NLAHE has been experimentally reported in various materials, yet studies on room-temperature NLAHE remain limited. In this work, we report the observation of the third-order NLAHE in the ferromagnetic metal ${\mathrm{Fe}}_3{\mathrm{GaTe}}_2$. The third-order NLAHE exhibits hysteresis as a function of external magnetic field, and the coercive field is the same as that of the anomalous Hall effect. Also, the third-order NLAHE remains observable up to the Curie temperature $\left(\sim 350\mathrm{K}\right)$. The scaling analysis suggests that the third-order NLAHE may arise from the Berry curvature quadrupole. Our work not only provides an approach for investigating magnetic materials via nonlinear electric transports, but also opens up possibilities for the future development of room-temperature third-order nonlinear electronic devices.

The ${\mathrm{He}}^{+}$ charge-state survival probability sets the absolute scale of quantitative low-energy ion scattering (LEIS), and a recent ${\mathrm{CaSiO}}_3$ study [J. Brötzner et al., Phys. Rev. B 113, 075405 (2026)] has shown that this probability depends on whether the backscattered trajectory involves one, two, or several collisions—suggesting that quantitative analysis ought to discriminate by collision history. How far this regime hierarchy generalizes is, however, an open question. This is addressed through scattering-regime-resolved binary collision approximation (BCA) simulations of ${\mathrm{He}}^{+}$ at 1–3 keV under grazing incidence $(\psi ={22}^{\circ })$ for four crystallographically distinct targets: $\alpha$-quartz ${\mathrm{SiO}}_2$, corundum $\alpha \text{−}{\mathrm{Al}}_2{\mathrm{O}}_3$, wurtzite GaN, and zincblende 3C-SiC. The calculations combine pair-specific Nordlund-Lehtola-Hobler potentials, position-dependent electronic stopping, Debye thermal vibrations, and a velocity-dependent Hagstrum kernel; statistically converged trajectory ensembles were accumulated for the high-statistics analysis. For $\alpha \text{−}{\mathrm{SiO}}_2$, GaN, and 3C-SiC, the standard ordering ${\langle P^{+}\rangle }_s>{\langle P^{+}\rangle }_d>{\langle P^{+}\rangle }_m$ is recovered, with single-to-multiple contrast $R_{s/m}\approx 1.5–2.2$. Corundum exhibits a qualitatively different behavior. When the backscattered ensemble is decomposed by the chemical identity of the final-collision atom, dual-scattering trajectories ending on the dominant Al sublattice show a charge survival below that of multiple-scattering ones at all five investigated energies. The sublattice-resolved inversion is highly significant—$19.7\sigma$ at 1 keV in the pooled three-seed ensemble, weakening monotonically to $3.7\sigma$ at 3 keV—and reproduces across three independent random seeds (per-seed significance $10.9-11.7\sigma$ at 1 keV). Because Al-ending trajectories make up $79\%\text{–}83\%$ of the backscattered population, the inversion also persists in the integrated signal $(P_d/P_m=0.59–0.80)$ despite the oppositely ordered minority O sublattice. The inversion is robust to a $\pm 30\%$ variation of the Hagstrum velocity parameter and survives detector-window selection. Tracking the recorded collision pairs reveals the cause: two Al atoms in the same atomic plane make up $52\%\text{–}72\%$ of the dual events in $\alpha \text{−}{\mathrm{Al}}_2{\mathrm{O}}_3$ (the fraction rising toward low energy; $\langle \left|\mathrm{\Delta }z\right|\rangle =0.29\AA$, small compared with the interlayer spacing), clustering at three characteristic in-plane separations of $\approx 2.6$, 4.7, and 7.1 Å that correspond to the first, second, and fourth Al-Al neighbor shells of corundum. Such a near-grazing intralayer trajectory remains within the high-density surface region considerably longer than a steep multicollision excursion, which enhances neutralization at the second encounter. These results indicate that quantitative regime-resolved charge-fraction analysis in ${\mathrm{He}}^{+}$ LEIS, while suggested by recent measurements on ${\mathrm{CaSiO}}_3$, must in general account for lattice topology and sublattice composition rather than collision count alone.

Diamond melting response at multimegabar pressures is of strong interest for understanding the interiors of giant planets and carbon-rich exoplanets, and for applications related to inertial confinement fusion. However, the high-pressure melting behavior of diamond remains poorly understood. Using plate impact experiments at the Sandia Z facility to achieve stresses up to 870 GPa, we show that melting onset in shock compressed [100] diamond single crystals and polycrystalline diamond occurs at 690 GPa. The [110] diamond response differs at stresses below the melting onset, showing that the approach to shock-induced melting depends on crystal orientation. In the solid-liquid mixed phase, the results for all diamond sample types coincide, demonstrating that the hydrodynamic assumption is appropriate after the melting onset. Our results provide an important benchmark for future theoretical studies, including the development of accurate multiphase equation of state models for diamond at high pressures and high temperatures.

High-harmonic generation in solids provides a powerful window into light-driven electron dynamics on attosecond timescales, yet the role of quantum fluctuations of the driving field remains largely unexplored. Here, we show that the quantum state of light offers a nonclassical degree of freedom for controlling strong-field dynamics in quantum materials. Using graphene driven by bicircular quantum light composed of counterrotating $\omega$ and $2\omega$ components, we theoretically predict that squeezing-induced fluctuations break the dynamical symmetry of the classical bicircular field and activate otherwise forbidden harmonics. By analyzing the helicity-resolved harmonic spectra, we uncover robust polarization signatures uniquely dictated by the squeezed mode's profile, including a relative-phase-controlled helicity switching in the lowest orders. Crucially, second-order intensity correlations reveal that these forbidden harmonics exhibit strongly enhanced, super-Poissonian photon-number fluctuations, confirming that they inherit and directly transduce the nonclassical statistics of the squeezed driving vacuum. Our findings establish forbidden harmonics as high-fidelity optical probes of the quantum state of light and provide additional opportunities at the intersection of quantum optics, strong-field physics, and lightwave engineering in quantum materials.

Two-dimensional systems with flat bands support correlated phases such as superconductivity. While twisted moiré systems, like twisted bilayer graphene, have revealed such states, they remain complex to control. Here, we study monolayer graphene under uniaxial periodic strain, which forms a quasi-one-dimensional moiré lattice that hosts two flat sublattice-polarized bands. When electron-electron interactions are included at the self-consistent Hartree level, we find features familiar from moiré flat-band systems, such as Fermi-level pinning to the Van Hove singularity and a Kohn-Luttinger-like pairing instability. In addition, we find strong interband enhancement of the pairing scale and higher-energy metastable electrostatic textures in enlarged supercells, with charge localized in selected regions of multiple unit cells.

Altermagnetism, featuring momentum-dependent spin splitting without net magnetization, has attracted growing interest for spintronics. We study a Fermi-Hubbard model with altermagnetic order arising from the spin-anisotropic hopping near half filling using constrained-path quantum Monte Carlo. Spin-dependent hopping breaks SU(2) symmetry and disrupts Fermi-surface nesting, giving rise to an altermagnetic state with momentum-space spin splitting but no net magnetization. We find that increasing anisotropy weakens equal-time antiferromagnetic correlations and enhances equal-time connected $d$-wave vertex correlations in the finite systems studied.

We employ a generalized approach to the master equation for driven open $N$-level ($N>2$) quantum systems using Lewis–Riesenfeld invariants, which avoids the driving-strength restrictions inherent to conventional approaches. We show that the invariant-based master equation provides a unifying generalized framework, which reduces to the frequently employed laboratory-frame master equations and the less frequently employed rotating-frame master equation framework under appropriate simplifications. Extending the prototypical two-level system, we show that the inclusion of another state coupled to the ground state via reservoir-induced dephasing gives rise to qualitatively new dissipative behaviors that are, in general, not captured by standard approximations. We also apply the invariant-based master-equation framework to a driven quantum dot coupled to a leaky cavity, demonstrating the framework's ability to capture relevant dissipative dynamics without additional assumptions. Our work paves the way for quantum-control applications in the presence of dissipation.

Frustration-driven quantum fluctuations, along with spin-orbit coupling and crystal electric field can give rise to exotic magnetic phenomena in rare-earth based quantum magnets. Here, we report the magnetic ground state properties of a buckled honeycomb lattice system, ${\mathrm{Nd}}_2{\mathrm{Te}}_4{\mathrm{O}}_{11}$, investigated through thermodynamic and muon spin relaxation (μSR) experiments. This compound crystallizes in monoclinic symmetry, where the $\mathrm{N}{\mathrm{d}}^{3+}$ ions are arranged in a buckled honeycomb lattice. Magnetization and heat capacity studies consistently indicate the formation of $J_{\mathrm{eff}}=1/2$ state in low temperature regime. In zero field, this compound exhibits the signature of magnetic ordering below ∼0.45 K, which is suppressed under applied magnetic field ≥ 30 kOe. In contrast, μSR results reveal the presence of persistent and strong spin fluctuations down to 0.05 K. Our finding points out that ${\mathrm{Nd}}_2{\mathrm{Te}}_4{\mathrm{O}}_{11}$ can be a potential candidate for proximate spin liquidlike behavior.

Kagome ferrimagnets are of fundamental interest because of their tunable magnetic, electronic, and topological properties, with potential applications for quantum-enabled technologies and spintronics. Here, we present the first direct measurement of the intrinsic timescale of the spin reorientation transition in the Kagome ferrimagnet $\mathrm{TbM}{\mathrm{n}}_6\mathrm{S}{\mathrm{n}}_6$. This material exhibits a magnetic phase transition near room temperature, where spins remain collinear while the total magnetic moment rotates from out-of-plane to in-plane. This reorientation has been attributed to the competing anisotropies of Tb and Mn, whose magnetic moments have very different temperature dependencies. By probing at the Mn $M$-edge using high-harmonic extreme ultraviolet pulses, we measure reorientation timescales between 5 and 18 ps, depending on the laser excitation fluence. Our model of the magnetization dynamics shows that this timescale is consistent with a spin reorientation driven by very large anisotropy energies, on meV energy scales. Our model also predicts the possibility of a ${180}^{\circ }$ reorientation of the out-of-plane moment, that could facilitate optically controlled magnetization switching between very stable ground states, for applications in spintronics or data storage.

The layer Hall effect (LHE) arises from the imbalanced Berry curvature distribution in different layers, which has been experimentally realized in the $\text{Mn}{\text{Bi}}_2{\text{Te}}_4$ thin films under perpendicular electric fields that break PT symmetry. Here, we present the LHE in a topological insulator heterostructure with intrinsically broken PT symmetry based on first-principles and tight-binding model calculations. Taking the topological insulator heterostructure ${\mathrm{Sb}}_2{\mathrm{Te}}_3/{\mathrm{Bi}}_2{\mathrm{Te}}_3$ as a concrete example, we demonstrate the feasibility of inducing the LHE only by coupling the top and bottom surfaces of ${\mathrm{Sb}}_2{\mathrm{Te}}_3/{\mathrm{Bi}}_2{\mathrm{Te}}_3$ heterostructure with magnetic insulator $\text{Mn}{\text{Bi}}_2{\text{Te}}_4$. Remarkably, an enhanced LHE with a broadened observable energy window and the $C=1/2$ parity anomaly state can be achieved by tuning the stacking order between the topological insulator and magnetic layers. This work offers an experimentally feasible platform for realizing the LHE, given the recent successful fabrication of epitaxial ${\mathrm{Sb}}_2{\mathrm{Te}}_3/{\mathrm{Bi}}_2{\mathrm{Te}}_3$ heterostructures.

Antiferromagnets provide a promising route for inducing perpendicular magnetic anisotropy (PMA) in adjacent ferromagnetic (FM) layers through exchange coupling, yet the respective roles of the magnetic phase stability, antiferromagnetic (AFM) spin configuration, and lattice distortion remain incompletely understood. Here we investigate the composition-dependent magnetic phase evolution of epitaxial fcc-like ${\mathrm{Co}}_x{\mathrm{Mn}}_{1\text{−}x}$ alloy films and its impact on PMA in ${\mathrm{Co}}_x{\mathrm{Mn}}_{1\text{−}x}/\mathrm{Co}/\mathrm{Fe}/\mathrm{Cu}\left(001\right)$ heterostructures. A transition from long-range AFM order ($x\le 0.47$) to ferromagnetism ($x\ge 0.71$) is identified, with a crossover near $x\approx 0.5–0.6$ within a single crystallographic framework. Pronounced PMA develops within the AFM regime and reaches a maximum at $x=0.2$, well separated from the AFM-FM boundary. The nonmonotonic dependence of PMA on composition, despite the systematic evolution of lattice distortion, indicates that lattice distortion alone cannot account for the observed PMA behavior. Layer-selective substitution experiments further reveal a pronounced depth dependence, indicating that the induced PMA is strongly influenced by magnetic interactions associated with the AFM spin configuration within the AFM layer, rather than by interfacial modification alone. These results indicate that the AFM-FM phase transition sets the composition range for PMA, long-range AFM ordering defines its onset, and the internal AFM spin configuration governs its magnitude. These findings further suggest that fcc-like ${\mathrm{Co}}_x{\mathrm{Mn}}_{1\text{−}x}$ alloys provide a model system for systematically tuning exchange-mediated magnetic anisotropy in epitaxial AFM/FM heterostructures.

We theoretically investigate the motion of a domain wall and a vortex in type-II superconductors driven by inhomogeneities of temperature or spin accumulation. The model consists of the time-dependent Ginzburg–Landau equation and the thermal or spin-diffusion equation, whose transport coefficients, such as the thermal and spin conductivities and the spin-relaxation time, depend on the order parameter and interpolate between their values in the superconducting and normal states. Numerical and analytical calculations indicate that the domain wall moves toward the higher-temperature region or the region with larger spin accumulation, where the order parameter is suppressed. We also derive analytical expressions for the vortex velocity and confirm the predicted direction of the vortex motion by numerical simulations. The dynamics of these topological defects can be understood as processes that reduce the loss of condensation energy. We also analyze the driving force, viscous force, thermal force, and force caused by the spin-accumulation gradient on the basis of momentum-balance relations.

Solid-state refrigeration based on caloric effects provides a sustainable alternative to conventional vapor-compression cooling technologies that rely on environmentally harmful refrigerants. Among these approaches, the barocaloric effect (BCE) has attracted considerable interest; however, structural phase transitions typically require high driving pressures, which severely restricts their practical applications. In this work, we investigate the BCE in a family of metal-organic frameworks (MOFs) featuring a wine-rack topology, revealing that these structures can achieve giant entropy changes under remarkably low pressures. Specifically, MIL-53(Al) exhibits an entropy change of $108\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$ at 40 MPa, while MIL-53(In) achieves $188\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$ at only 15 MPa, comparable to the required pressure in commercial vapor-compression refrigeration. A physically interpretable model constructed using the SISSO (sure independence screening and sparsifying operator) algorithm reveals that the low driving pressure in these systems primarily originates from a small bulk modulus and a large pore volume; meanwhile, lower linker mass density and larger metal-ion radius effectively attenuate local steric hindrance and interatomic interactions, similarly facilitating the low-pressure-driven phase transitions. Thermodynamic decomposition of the energy demonstrates that this giant entropy change is dominated by the potential energy variation associated with framework deformation, wherein the van der Waals interactions between the organic linkers play a crucial role. Microscopic phonon dynamics analysis further elucidates that the pressure-induced framework contraction concentrates substantial local stress on the carbon atoms, suppressing their low-frequency vibrational modes and thereby leading to a reduction in the vibrational entropy of the system. These results identify wine-rack MOFs as promising candidates for low-pressure barocaloric refrigeration, providing structural design principles for high-performance solid-state cooling materials.

A path-integral approach to quantum acoustics is developed here. In contrast to the commonly utilized particle perspective, this emerging field brings forth a long-neglected yet essential wave paradigm for lattice vibrations. Within the coherent state picture, we formulate a non-Markovian stochastic master equation that captures the exact dynamics of any system with coupling linear in the bath coordinates and nonlinear in the system coordinates. We further demonstrate the capability of the presented master equation by applying the corresponding procedure to the well-known Fröhlich model. In general, we establish a solid foundation for quantum acoustics as a kindred framework to quantum optics, while paving the way for deeper first-principles explorations of nonperturbative system dynamics driven by lattice vibrations.