The spin properties of excitons and charge carriers in ${\mathrm{CsPbBr}}_3$ lead halide perovskite crystals are investigated by spin-dependent light scattering in magnetic fields up to 10 T. Spin-flip Raman scattering spectra measured under resonant excitation of exciton-polaritons show a rich variety of features provided by the Zeeman splittings of excitons and of electrons and holes interacting with the excitons. The magnitudes and anisotropies of their Landé $g$ factors are measured. A detailed consideration of the responsible mechanisms is presented and discussed in relation to the experimental data, in particular on the polarization properties of the Raman spectra. We consider several mechanisms for the combined spin-flip Raman scattering processes involving resident carriers and photoexcited excitons and suggest new ones, involving trions in the intermediate scattering state. A double electron spin-flip caused by the exciton interaction with two localized or donor-bound electrons is revealed. The spectral lines of Brillouin light scattering on exciton-polaritons shift in energy and become polarization-sensitive in magnetic field, evidencing the splitting of the exciton-polariton dispersion.

We investigate topological band structures of a kagome system coupled to a circularly polarized cavity mode, using a model based on a muffin-tin potential and quantum light-matter interaction. We show that Chern insulating phases emerge in the cavity-embedded kagome system due to the light-matter interaction that breaks time-reversal symmetry. We also find that a nearly flat band can be topologically nontrivial with a nonzero Chern number. By varying the light-matter interaction, we also reveal that topological phase transitions occur between different Chern insulating phases in the ultrastrong coupling regime. The phase transitions change the sign of the Chern number, switching the direction of the edge current. We demonstrate the existence of topological edge modes in the cavity-embedded kagome Chern insulators by constructing a low-energy effective tight-binding model.

We investigate far-field radiation of energy, linear momentum, and angular momentum from two-dimensional electron systems, focusing on metallic thin films described by the Drude conductivity. Using the Keldysh formalism within the nonequilibrium Green's function framework, we derive analytical expressions for radiative power, force, and torque. To enable angular momentum radiation, an out-of-plane magnetic field is applied to break reciprocity, resulting in gyrotropic terms in the permittivity tensor. By approximating the emitter as a thin film, the photon Green's functions can be solved analytically. Expressions for the Poynting vector and Maxwell's stress tensor can subsequently be extracted from the lesser Green's function, which governs the field correlations. The final radiation formulas can be expressed in terms of Fresnel coefficients, revealing an insightful connection to energy conservation via Kirchhoff's law. Using the Wigner transform, the analytical expression for the radiative torque can also be related to the generalized Fresnel coefficients. Numerical calculations based on the optical conductivity of bismuth are presented to corroborate the analytical results. These results provide a unified framework for energy, momentum, and angular momentum radiation in gyrotropic thin films.

Reducing computational scaling for simulating non-Markovian dissipative dynamics using artificial neural networks is both a major focus and formidable challenge in open quantum systems. To enable neural quantum states (NQSs), we encode environmental memory in dissipatons (quasiparticles with characteristic lifetimes), yielding the dissipaton-embedded quantum master equation (DQME). The resulting NQS-DQME framework achieves a compact representation of both many-body correlations and non-Markovian memory. Benchmarking against numerically exact hierarchical equations of motion confirms NQS-DQME maintains comparable accuracy while enhancing scalability and interpretability. This methodology opens different paths to explore non-Markovian open quantum dynamics in previously intractable systems.

Altermagnetic (AM) order, a recently discovered magnetic state, has attracted intense research interest for its potential applications in spintronic and quantum technologies. Here, we theoretically investigate the AM state in the Lieb lattice, a prototypical two-dimensional lattice, using the Hubbard model. We show that AM order emerges with only moderate electronic correlations. Strikingly, spin-orbit coupling drives the system into a topological phase exhibiting a new quantum spin Hall effect (QSHE) with spin-biased topological edge states in one-dimensional nanoribbons. These edge states possess different localizations and velocities, and hence may produce spin and charge currents, fundamentally distinct from those in conventional topological insulators with spin degeneracy. This novel spin-biased QSHE in the AM Lieb lattice unveils exciting opportunities for both fundamental studies and innovative device concepts, motivating immediate experimental exploration.

The detection of considerable spin frustration in honeycomb cobalt oxide compounds indicates the presence of sizable Kitaev interactions in these systems, enlarging the pool of Kitaev spin liquid candidates. Several key questions remain to be answered, as basic as the mechanisms behind Kitaev couplings in ${\mathrm{Co}}^{2+}$ $t_{2g}^5{e}_g^2$ magnets. Analyzing the quantum chemistry of interacting magnetic moments in ${\mathrm{Na}}_3{\mathrm{Co}}_2{\mathrm{SbO}}_6$, a representative $LS$-coupled $t_{2g}^5{e}_g^2$ oxide, we find that the Kitaev and off-diagonal $\mathrm{\Gamma }$ interactions are substantial and antiferromagnetic but somewhat weaker than the Heisenberg contribution. All nearest-neighbor couplings feature massive contributions from direct Coulomb exchange and/or on-site multiconfigurational dressing, mechanisms not considered so far in descriptive models of Kitaev-Heisenberg magnetism. These findings call for systematic wave function quantum chemical studies to understand direct-indirect exchange synergies in Kitaev-Heisenberg magnets and how to possibly tune intersite couplings toward the Kitaev spin liquid ground state.

Achieving the ultimate lower limit of thermal conductivity is essential for advancing thermal management, thermoelectric energy conversion, and phononic engineering. Here, we integrate Bayesian optimization with machine-learning-potential molecular dynamics to discover stacking configurations in graphene/twisted-${\mathrm{MoS}}_2$ $(\mathrm{Gra}/\mathrm{T}\text{−}{\mathrm{MoS}}_2)$ heterostructures that exhibit an exceptionally low crossplane thermal conductivity of $0.006\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}$, which is 3–4 times lower than that of typical ultralow-thermal-conductivity porous materials $(0.02–0.04\mathrm{W}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1})$, surpassing the conventional lower bound of thermal conductivity in solid materials. Phonon transmission and spectral analyses reveal that this extreme thermal insulation originates not merely from phonon localization but from the overdamped regime of phonon dynamics, where strong interlayer asymmetry and disorder suppress the restoring forces that sustain oscillatory motion. In this regime, phonons lose their quasiparticle nature, and heat conduction transitions from propagating vibrations to localized energy dissipation. This work introduces phonon overdamping as a physical mechanism governing the ultimate limit of lattice thermal conductivity and establishes a data-driven framework for designing next-generation materials with tunable and ultralow heat transport.

Intrinsic spin-orbit coupling (SOC) in graphene is dominated by the $d$ orbitals, and hence, effective three orbital models with $p_z$ and $d$ orbitals faithfully reproduce the nontrivial band structure of the low-energy bands. However, bending and deformation are commonly described in the literature in terms of the $p_z$- and $\sigma$-band orbitals, owing to the assumption that the rather empty $d$ orbitals have a marginal effect. We show in this work that the role of $d$ orbitals is critical not only to determine spin-orbit gaps but also to account for curvature-induced spin splitting. Here we employ a multiorbital tight-binding model including the $s$, $p$, and five $d$ orbitals of bent graphene nanoribbons with zigzag edges. We scrutinize the effects of the $p$ or $d$ orbitals on the intrinsic SOC splitting and on the curvature-induced Rashba-type SOC due to the onset of orbital hybridization. Whereas the former causes the edge spin to align in the direction perpendicular to the graphene plane, the latter imposes an in-plane quantization. We find that the critical curvature to observe this in-plane quantization is increased by more than 100% when the effect of the $d$ orbitals is included, highlighting their importance. Moreover, we encounter localized bound states under sinusoidal corrugation, owing to an effective bending-induced gauge potential, which leads to a pseudomagnetic field and subsequent Landau quantization. We stress that our findings highlight the importance of $d$ orbitals in the theoretical modeling of spintronic devices and experiments in graphene-based nanostructures.

Alloyed mercury cadmium chalcogenide semiconductors are promising materials for photoemission and photodetector applications in the near- to far-infrared regions of the electromagnetic spectrum, with ${\mathrm{Hg}}_x{\mathrm{Cd}}_{1-x}\mathrm{Te}$ already used widely in focal plane arrays in the mid- to far-infrared. While ${\mathrm{Hg}}_x{\mathrm{Cd}}_{1-x}\mathrm{S}$ and ${\mathrm{Hg}}_x{\mathrm{Cd}}_{1-x}\mathrm{Se}$ alloys are also promising for these applications, especially in their nanocrystalline forms, characterization of their optical properties has been limited. Using density functional theory, we calculate the electronic structure, effective masses, Luttinger parameters, and optical response functions of zinc blende CdS, HgS, CdSe, and HgSe. We further predict the dielectric function of ${\mathrm{Hg}}_x{\mathrm{Cd}}_{1-x}\mathrm{S}$ and ${\mathrm{Hg}}_x{\mathrm{Cd}}_{1-x}\mathrm{Se}$ alloys in thermodynamic equilibrium at 300 K for compositions between $x=0$ to $x=1$ using a cluster expansion approach with the generalized quasichemical approximation. We find that spin-orbit coupling increases the band gap by up to 0.1 eV, and the use of a hybrid functional increases the alloy band gaps up to 1 eV. We map the $E_1$ and $E_2$ optical critical point peaks and derive the nonlinear relationship between peak energy and composition, resulting in bowing parameters that are distinct from those of the band edges. These findings can serve as a reference for identifying mercury cadmium chalcogenide alloy composition from optical spectroscopic measurements in the visible and ultraviolet spectra.

The description of the entanglement dynamics of monitored noninteracting fermions, including the existence of measurement-induced phase transitions (MIPTs), is a challenging problem with conflicting results in the literature. The mapping of the problem onto a nonlinear sigma model (NLSM) indicates that relatively large lattice sizes are required to determine the nature of the entanglement entropy in the thermodynamics limit. Here we address this problem numerically for monitored noninteracting fermions with $U\left(1\right)$ symmetry. The use of graphics processing unit techniques, even with outdated hardware, makes it possible to reach much larger lattice sizes $[L=16384$ and $160\times 160$ in one (1D) and two (2D) dimensions, respectively] than in previous studies, which enables us to characterize quantitatively the entanglement dynamics. In 1D, we show that to confirm the absence of a MIPT, for both projective and homodyne measurements, predicted by the NLSM, it is necessary to reach $L\sim 10000$. In 2D, also as predicted by the NLSM, we observe for both protocols a MIPT at a finite monitoring rate characterized by scale invariant mutual information. The critical monitoring strength depends on the protocol while the critical exponent $\nu \approx 1.3$ governing the approach to the MIPT is similar in both cases. These features are not correctly predicted by the NLSM. Our results pave the way for a fully quantitative description of the entanglement dynamics of monitoring quantum systems.

We analyze a classical Heisenberg spin model on the simple cubic lattice which is invariant under time reversal and contains multiple chiral spin interactions. The modeled dynamics is appropriate either for local moments coupled to itinerant Weyl electrons or localized electrons with a strong spin-orbit coupling that would produce a Weyl spectrum away from half filling. Using a Monte Carlo method, we find a robust $4Q$ bipartite lattice of hedgehogs and antihedgehogs which melts through a first order phase transition at a critical temperature in certain segments of the phase diagram. The density of hedgehogs is a nonlinear function of the Dzyaloshinskii-Moriya interaction and a linear function of the multiple-spin chiral interaction which plays the fundamental role of a “magnetic flux” or a hedgehog chemical potential. These findings are related to the observations of hedgehog lattices in MnGe, ${\mathrm{MnSi}}_{1-x}{\mathrm{Ge}}_x$, and ${\mathrm{SrFeO}}_3$ and indirectly support the possible existence of incompressible quantum-disordered hedgehog liquids.

In this work, we propose a one-dimensional $t\text{−}J\text{−}K\text{−}U$ model, where itinerant spin-1/2 fermions are coupled to a spin-1/2 Heisenberg chain via a Kondo interaction $J_k$. Depending on the sign of $J_k$, the system realizes either a high-spin or low-spin ground state. Using the density matrix renormalization group (DMRG) calculations, we demonstrate the emergence of a pairing density wave (PDW) with wave vector $Q=\pi$ in this model. In the low-spin state, the ground state of the system is identified as a Luther-Emery liquid. In the high-spin state, superconducting pairing correlations are suppressed, and a quasi-long-range (QLR) spin density wave (SDW) emerges. In addition to the Kondo coupling $J_K$, strong correlations among the itinerant electrons also play a significant role in stabilizing these density wave orders. We suggest that this model may be realized in a ${\mathrm{Ni}}^{2+}$ chain with Ni in the $d^8$ configurations. Although superconductivity has not yet been observed in these materials, charge and spin ordering phenomena have been widely reported. Our results provide a potential pairing mechanism, indicating the possible existence of these intertwined orders in nickelates.

We investigate the localization properties of non-Hermitian bound states in the nonreciprocal two-particle Hubbard model. Remarkably, under the conditions of finite-size truncation, non-Hermitian skin effect (NHSE), bound-state localization (BSL), and topological edge localization will compete with each other, giving rise to diverse density profiles. When BSL and NHSE favor different direction of localization, bound states can either be destroyed or survive depending on the strength of nonreciprocal tunneling and two-particle interaction. For the unbound scattering states, unlike the exponential localization predicted by the Hatano-Nelson model, interaction can get the total localization split into multiple centers. Meanwhile, apart from non-Hermitian bound states out of continuum, non-Hermitian bound states in continuum can also be achieved as a by-product of the multiple independent tunneling factors. Besides, we not only consider the bosonic but also the fermionic interacting model, where in the latter case, localization properties are greatly enriched by the configuration space boundary caused by Pauli exclusion rule, and the non-Hermitian near-bound states are proposed. Finally, to achieve nontrivial topology, we include terms taking the form of two-photon tunneling, and the competition among all three localization mechanisms is analyzed via the transfer matrix approach, where the unique phenomenon, NHSE oriented by two-particle interaction, is demonstrated.

The realization of a Weyl semimetal hosting a minimal single pair of Weyl points (WPs) is a long-standing goal for fundamental studies of chiral fermions, yet remains elusive in nonmagnetic electronic materials. Here, through first-principles calculations and symmetry analysis, we propose a stable, all-${\mathit{sp}}^2$ hybridized three-dimensional carbon allotrope, $\mathrm{HSRDC}\text{−}{\mathrm{C}}_{28}$. Crucially, its low-energy bands host exactly one pair of WPs at the time-reversal-invariant momenta $\mathrm{\Gamma }$ and M, carrying topological charge $C=\pm 2$, with the sign of the charge tied to the structural chirality. These WPs exhibit characteristic anisotropic dispersions, linear along the $C_4$-rotation axis and quadratic in the plane perpendicular to this axis, and are protected by $C_4$-rotation and time-reversal symmetries. The calculated surface states exhibit ultralong double-Fermi arcs connecting the projections of $\mathrm{\Gamma }$ and M, spanning the entire surface Brillouin zone and providing unambiguous signatures for experimental verification. Our work not only expands the landscape of topological quantum states but also offers a nonmagnetic electronic platform for exploring the physics associated with minimal double-Weyl fermions.

High-pressure, high-temperature synthesis is a valuable technique for the investigation of binary systems because it enables the stabilization of new phases that are metastable at ambient pressure and temperature. Because of its low bulk modulus, the atomic radius of Mg undergoes a large shrinkage above the GPa range, which can lead to the stabilization of potential new structures with other transition-metal (TM) elements. The present study reports on the synthesis and characterization of a Mg–Fe intermetallic phase in aser-heated diamond anvil cells (LH-DAC) on the ID27 beamline of the ESRF, above $1200{}^{\circ }\mathrm{C}$ and from 30 GPa to 60 GPa. The compound crystallizes in the cubic $P{4}_{1}32$ space group with $\beta$-Mn structure as a prototype (Strukturbericht designation $A13$). Several isobaric heating experiments as well as a temperature-controlled decompression were performed on this $A13$ phase, observed to be stable in two different compositions of Fe–Mg samples obtained by physical vapor deposition (PVD) (48 at.% Mg and 68 at.% Mg). Additional first-principles calculations on ordered and disordered phases were also performed to support the experimental work. A thermal equation of state of the $A13-{\mathrm{Fe}}_2{\mathrm{Mg}}_3$ phase is proposed, as well as a diagrammatic interpretation, taking into account the experimental results with the corresponding binary phase diagrams on the Mg-rich side.