The design of three-dimensional (3D) superlattices from known two-dimensional (2D) and 3D topological units provides a versatile platform for engineering spin-dependent electronic states. While most previous studies have focused on topological surface states (TSS), other prominent spectral features have received less attention. In the prototypical nature superlattice compound $\mathrm{B}{\mathrm{i}}_1\mathrm{S}{\mathrm{e}}_1$ from the ${\left[\mathrm{B}{\mathrm{i}}_2\right]}_x{\left[{\left(\mathrm{Bi},\mathrm{Sb}\right)}_2{\left(\mathrm{Te},\mathrm{Se}\right)}_3\right]}_y$ family, angle-resolved photoemission spectroscopy (ARPES) reveals a dominant Dirac-like band whose spin texture has remained unresolved. Here, using low-temperature cleavage, scanning tunneling microscopy (STM), circular dichroism ARPES (CD-ARPES), and ab initio calculations, we achieve uniformly terminated $\mathrm{B}{\mathrm{i}}_1\mathrm{S}{\mathrm{e}}_1\left(0001\right)$ surfaces, enabling unambiguous identification of its spin polarization. We find that this Dirac-like state exhibits a reversed in-plane helical spin texture inherited from the residual electronic remnant of TSS of the $\mathrm{B}{\mathrm{i}}_2\mathrm{S}{\mathrm{e}}_3$ subunits, persisting on the “topologically” dark (0001) surface despite the absence of global protection. A conduction band minimum showing dichroism consistent with Rashba-type splitting is also observed, similar to the surface state on bulk $\mathrm{B}{\mathrm{i}}_2\mathrm{S}{\mathrm{e}}_3$. The close correspondence between our findings and those reported in identically terminated $\mathrm{B}{\mathrm{i}}_1\mathrm{T}{\mathrm{e}}_1$ suggests that such residual-TSS derived Dirac states are a general feature of ${\left[\mathrm{B}{\mathrm{i}}_2\right]}_x{\left[{\left(\mathrm{Bi},\mathrm{Sb}\right)}_2{\left(\mathrm{Te},\mathrm{Se}\right)}_3\right]}_y$ superlattices. The experimental–theoretical strategy demonstrated here offers a framework for exploring spin-textured states in engineered topological heterostructures.

The spatial distribution of interfacial spin states is a critical factor governing the efficiency of spin-injection and spin-detection in spintronic devices. In this study, we use angle-resolved photoemission spectroscopy (ARPES) to investigate the evolution of the two types of spin-polarized surface states of the topological insulator $\mathrm{S}{\mathrm{b}}_2\mathrm{T}{\mathrm{e}}_3$—the topological surface states and the Rashba-type surface states (RSS)—upon electron doping. Our detailed analysis reveals that the electronic structure undergoes a modification that goes beyond a simple rigid band shift. Specifically, we observe that the electron doping reduces the ARPES intensity of one of the spin-split RSS branches. Calculations based on the density functional theory reveal that the decrease in intensity results from a change in the depth distribution of the probability densities. These results demonstrate that charge transfer can redistribute the near-surface weight of spin-polarized states along the surface normal, providing a depth degree of freedom for interfacial spins.

Phase transition in van der Waals (vdW) two-dimensional (2D) materials is an effective approach to create novel and tunable electronic states for potential applications in next-generation quantum electronics. Here, we propose an unusual non vdW phase transition behavior in 2D layered transition metal dichalcogenides (TMDs). As interlayer distance decreases below the common vdW gap upon pressure, interfacial ligand-ligand chemical bonds could form to stabilize the system and result in a phase transition to a non vdW structure, which exhibits interesting electronic and magnetic properties very different from the pristine vdW one. Based on first-principles calculations, we predict stable non vdW phase transitions in $\mathrm{Cr}{\mathrm{S}}_2$ and other TMD bilayers, characterized by the formation of interlayer S-S single covalent bonds, which is accompanied by metal-semiconductor, nonmagnetic-magnetic and/or magnetic phase transitions. These findings elucidate a general phase-transition mechanism in vdW 2D materials driven by out-of-plane pressure, suggesting a viable strategy to exploring potential quantum electronic states for diverse functional applications.

We investigate the fluctuation-induced Casimir interactions between two parallel graphene sheets carrying steady-state drift currents. The graphene properties are modeled based on the shifted Fermi disk model to capture the nonequilibrium optical response of the system. We find that the drift current introduces a repulsive correction to the perpendicular to the layers Casimir interaction, thereby reducing the overall attractive force. Although the correction is repulsive, it does not overcome the underlying attraction between the layers. It also generates a lateral force that opposes the carrier flow direction. Both contributions are studied in terms of distance and drift velocity functionalities showing pathways for Casimir force control.

Floquet engineering offers a powerful route to enhance emission in time-modulated media. Here, we investigate the influence of time-modulated permittivity in silicon carbide on its intensity spectrum. We consider both the nonequilibrium Green's function approach and the macroscopic quantum electrodynamics approach, and establish their formal compatibility by deriving the Lippmann-Schwinger equation in both cases. To analyze spectral features, we propose several methods for decomposing the electric field into positive- and negative-frequency components, along with the criteria required for physical consistency. Our analytical and numerical results show that when defined appropriately, the intensity spectrum avoids divergence, though the resulting enhancement remains modest. These findings provide a unified theoretical foundation for modeling time-dependent media, and reinforce the utility of Floquet engineering as a versatile platform for tailoring emission dynamics.

Band structure unfolding is a key technique for analyzing and simplifying the electronic band structure of large, internally distorted supercells that break the primitive cell's translational symmetry. In this work, we present an efficient band unfolding method for atomic orbital (AO) basis sets that explicitly accounts for both the nonorthogonality of atomic orbitals and their atom-centered nature. Unlike existing approaches that typically rely on a plane-wave representation of the (semi)valence states, we here derive analytical expressions that recast the primitive cell translational operator and the associated Bloch functions in the supercell AO basis. In turn, this enables the accurate and efficient unfolding of conduction, valence, and core states in all-electron codes, as demonstrated by our implementation in the all-electron ab initio simulation package fhi-aims, which employs numeric atom-centered orbitals. We explicitly demonstrate the capability of running large-scale unfolding calculations for systems with thousands of atoms and showcase the importance of this technique for computing temperature-dependent spectral functions in strongly anharmonic materials using CuI as example.

We study the two-dimensional $t\text{−}J$ model at finite temperature directly in the thermodynamic limit using purification represented by an infinite projected entangled-pair state (iPEPS). We reach temperatures down to $T/t=0.1$ and hole concentrations up to $1-n\simeq 0.25$, and provide benchmark thermodynamic-limit results for the specific heat, uniform susceptibility, and charge compressibility. We identify a susceptibility maximum $T^{*}$ that tracks the buildup of short-range antiferromagnetism and a shallow compressibility enhancement upon cooling in the same doping window. To expose the underlying microscopic mechanism, we introduce dopant-conditioned multipoint correlators that quantify how holes reorganize nearby exchange: Single holes weaken adjacent antiferromagnetic bonds, while nearest-neighbor hole pairs produce a cooperative response that reinforces antiferromagnetism on the parallel plaquette edge. Over the same parameter window, $d$-wave pairing correlations remain short-ranged. These results provide experiment-compatible thermodynamic-limit benchmarks and establish dopant-conditioned correlators as incisive probes of finite-temperature spin-texture reorganization in doped Mott insulators.

${\text{La}}_2{\text{Ni}}_7$ is an itinerant magnetic system with a small ordered moment of $\sim 0.1{\mu }_B/\text{Ni}$ and a series of antiferromagnetic (AFM) transitions at $T_1=61.0\mathrm{K}, T_2=56.5\mathrm{K}$, and $T_3=42.2\mathrm{K}$. $M\left(H\right)$, and $\rho \left(H\right)$ isotherms as well as constant field $M\left(T\right)$ and $\rho \left(T\right)$ measurements on single-crystalline samples manifest a complex, anisotropic $H\text{−}T$ phase diagram with multiple phase lines. Here we present the growth and characterization of single crystals of the ${\text{La}}_2{\text{(Cu}}_x{\text{Ni}}_{1-x}{)}_7$ series for 0 $\le x\le$ 0.181. We measured powder x-ray diffraction and composition, as well as anisotropic temperature- and field-dependent resistivity, temperature- and field-dependent magnetization, and temperature-dependent heat capacity on these single crystals. Using the measured data we infer a transition temperature-composition $\left(T\text{−}x\right)$ phase diagram for this system to study the evolution of the AFM ordering upon Cu substitution. For $0\le x\le 0.097$, the system remains magnetically ordered at base temperature with $x\le$ 0.012, showing signs of multiple AFM ordering temperatures. For the higher substitution levels $0.125\le x\le 0.181$, there are no signatures of magnetic ordering, but anomalous features in resistance and heat capacity data are observed which are consistent with the Kondo effect in this system. The intermediate $x=0.105$ sample lies between the magnetic ordered and the Kondo regime and is in the vicinity of the AFM quantum critical point (QCP). Thus, ${\text{La}}_2{\text{(Cu}}_x{\text{Ni}}_{1-x}{)}_7$ is an example of a small moment system that can be tuned through a QCP. Given these data combined with the fact that the ${\text{La}}_2{\text{Ni}}_7$ structure has kagomelike, Ni sublattices running perpendicular to the crystallographic $c$ axis, and a predicted $3d$-electron flat band that contributes to the density of states near the Fermi energy, ${\text{La}}_2{\text{(Cu}}_x{\text{Ni}}_{1-x}{)}_7$ becomes a promising system to host and study exotic physics.

Hidden effects represent intriguing physical phenomena that are globally forbidden yet locally permitted by symmetry. Applying Helmholtz's theorem to spin vector fields, we can decompose spin polarization into its fundamental components: while hidden Rashba (purely solenoidal), Dresselhaus (mixed solenoidal/irrotational), and Zeeman-type (constant-field) spin textures have been extensively studied, their purely irrotational counterpart—hidden radial spin polarization (HRSP)—has remained mostly unexplored. In this Letter, we demonstrate the existence of symmetry-protected HRSP in crystals whose sublattices host one of the chiral point groups (${\mathrm{D}}_3, {\mathrm{D}}_4, {\mathrm{D}}_6$, T, O). We show that this phenomenon arises in both centrosymmetric and noncentrosymmetric systems, mediated globally by inversion and mirror operations, respectively. Through spin-orbit coupling, these systems exhibit distinctive hedgehoglike and compensated spin textures in momentum space. Our first-principles calculations on three prototypical materials—centrosymmetric layered ${\mathrm{NbTe}}_4$, centrosymmetric chained ${\mathrm{Pb}}_4\mathrm{Pt}$, and noncentrosymmetric layered ${\mathrm{Sb}}_5{\mathrm{IO}}_7$—provide compelling validation. These findings not only deepen our fundamental understanding of hidden spin phenomena but also significantly expand the design space for novel spintronic materials.

The electron-phonon Wannier interpolation (EPWI) method is an efficient way to compute electron-phonon interaction (EPI) properties accurately. In this study, we present a GPU-accelerated implementation of the EPWI method for computing transport properties, followed by a performance analysis. The implementation is tested on common systems such as aluminum and silicon. The results show complete consistency with those obtained through CPU computations. The proposed algorithm computes the conductivity of aluminum in 20 min on a single NVIDIA Tesla V100 GPU, using a ${200}^3$ electron and phonon sampling grid. This is 54 times faster than the CPU-based algorithm running on two nodes of Intel Xeon Platinum 8260 CPUs. The impressive acceleration is achieved by carefully designing the algorithm to reduce the computational workload and exploit the specific features of the GPU. The approach can also be extended to GPU codes for other EPI-related properties.

We theoretically investigate the Casimir-Lifshitz torque between two stacks of cholesteric DNA embedded in water and surrounded by silica substrates. We utilize the spiral staircase model combined with the Rayleigh method to describe the geometric structure of DNA films. It is found that for a specific nucleotide base pairing, the adenine-thymine (AT)10 oligomer, the torque amplitude exceeds four times that predicted by the bulk dielectric function model, and the finite-thickness effect remains significant even at distances two orders of magnitude smaller than the DNA stacking thickness. This highlights the need for realistic modeling of the DNA liquid crystal based on the proper dielectric function and geometry. These results may have applications in the emerging field of DNA-based nanotechnology.

Topological braiding of complex bands in non-Hermitian systems has emerged as a powerful framework for exploring novel topological phases. Although extensively investigated in static and Floquet-Bloch settings, such braiding is conventionally characterized by finite braid groups ${\mathrm{B}}_q$, in which only subsets of bands participate in braiding processes. Here, we unveil a new class of spectral topology in non-Hermitian space-time crystals, called the global Floquet-band braiding, where all Floquet bands intertwine globally in generalized momentum-energy space. This phenomenon arises from the space-time translational symmetry, which enables single-orbital band crossings. The resulting braiding involves an infinite number of Floquet bands, referred to as infinite-band braiding. Under the rational space-time modulation, the multiband periodicity endows the system with a cylindrical topology, allowing the global braiding structure to be effectively described by cylindrical braid groups $\mathrm{C}{\mathrm{B}}_q$. Crucially, this topology transcends the conventional framework of finite braid groups, marking a fundamental expansion of non-Hermitian spectral topology. In experiments, we implement a reconfigurable topolectrical circuit that realizes a part of the space-time band braiding. By exploiting space-time translation symmetry, we reconstruct the global Floquet-band braiding characterized by $\mathrm{C}{\mathrm{B}}_5$. Our work establishes the non-Hermitian space-time crystal as a novel platform for engineering unprecedented non-Hermitian topological matter beyond existing paradigms.

We considered a planar Josephson junction which is composed of two $s$-wave superconducting contacts deposited on the top of a thin antiferromagnetic (AFM) disordered metal film. In such a system, noticeable Josephson currents may be observed if contacts are just nanometers away from each other. It is shown that the excitation of AFM by magnons results in a strong enhancement of the stationary current through much longer junctions, whose length may be comparable to the coherence length of superconducting correlations in a nonmagnetic metal. Such a current is calculated at the weak tunneling amplitude of electrons between superconducting contacts and AFM. The problem is considered for nonequilibrium Green functions in the second-order perturbation theory with respect to the electron-magnon interaction. A spin-orbit torque oscillator was taken as a possible source of long-wavelength classic magnetic waves. This work predicts a strong effect of magnons on superconducting proximity effect in AFM, with promising applications in superconducting spintronics.

We demonstrate the successful simulation of $\sqrt{Z}$-, $\sqrt{X}$-, and $X$-quantum gates using Majorana zero modes (MZMs) that emerge in magnetic vortices located in topological superconductors. We compute the transition probabilities and geometric phase differences accounting for the full many-body dynamics and show that qubit states can be read out by fusing the vortex core MZMs and measuring the resulting charge density. We visualize the gate processes using the time- and energy-dependent nonequilibrium local density of states. Our results demonstrate the feasibility of employing vortex core MZMs for the realization of fault-tolerant topological quantum computing.

The Fe-O system is fundamental to understanding the composition and properties of the Earth's core. Recent studies have suggested the possible existence of stable, iron-rich ${\mathrm{Fe}}_n\mathrm{O}$ compounds at around 215 GPa. Here, we performed crystal-structure searches and fully anharmonic free-energy calculations to investigate the Fe-FeO system under inner-core conditions. We identified ${\mathrm{Fe}}_2\mathrm{O}$ as a stable phase and constructed its high P-T phase diagram. ${\mathrm{Fe}}_2\mathrm{O}$ undergoes a hexagonal-to-tetragonal transition with increasing pressure and temperature. It remains thermodynamically stable against decomposition into Fe and FeO from 200 to 400 GPa and at high temperatures. Although oxygen has been considered nearly absent in the inner core due to its limited solubility, these results suggest that oxygen can, in fact, be incorporated into the solid inner core in the form of an $\mathrm{Fe}+{\mathrm{Fe}}_2\mathrm{O}$ mixture, and can match PREM densities for 53 mol % ${\mathrm{Fe}}_2\mathrm{O}$. Our work has the potential to lead to a significant revision of the current understanding of the core's structure and composition.

For more than 100 years, melting has been thought to be governed by the Lindemann criterion, which assumes that a crystal melts when, upon heating, the growing atomic vibration amplitudes become sufficiently large to destabilize its crystalline lattice. However, it is unclear why the viscosities η or the related relaxation times τ of the resulting liquids, measured directly at the melting point $T_{\mathrm{m}}$, differ by up to nine decades, depending on the material. Based on the empirical rule that the ratio of the glass-transition temperature and $T_{\mathrm{m}}$ is about 2/3, here we show that this strong variation is due to differences in the liquid's fragilities, a property associated with pronounced non-Arrhenius behavior and often ascribed to cooperative motions. We propose that, without cooperativity, all crystals would melt into liquids with a universal viscosity value and relaxation time. Hence, the real melting point is only partly determined by the Lindemann criterion and is strongly enhanced by the cooperativity of the resulting liquid. Our findings are corroborated by the determination of the idealized, fragility-free melting temperatures and of the corresponding η and τ values for various example materials.

A spin-$s$ variable-range interacting Ising model may display qualitatively different behaviors depending on the fall-off rate of the interactions, as already seen in equilibrium studies of spin-1/2 systems. We propose a dynamical method using weighted graph states, generated through time evolution that confirms the existence of the transition point in the fall-off rate for the spin-$s$ Ising model. Moreover, the dependence of local dimension on information spreading and multipartite entanglement profile in this model remains unclear, which we establish here. In particular, our analysis shows that the maximum of genuine multipartite entanglement (GME) with the fall-off rate serves as a clear indicator of the information spreading, which aligns with changes in the profile of the Lieb-Robinson bound. Further, in the case of an open chain, the spread of information is related to the divergence in the first derivative of GME. Additionally, we validate this signature by performing a scaling analysis of the time-averaged mutual information.

Electron quantum transport in disordered systems has attracted great interest because of its fundamental importance in condensed matter physics. Although the incipient Anderson localization related to electron-phonon scattering or electron-electron interactions has been reported in several nonmagnets and ferromagnets, it has not been reported in antiferromagnets so far, and the role of electron-magnon scattering remains elusive. In this work, we report the observation of incipient Anderson localization and dimensional crossover in antiferromagnetic $\gamma$-FeMn films. Temperature ($T$)-dependent conductivity ($\sigma$) exhibits an additional linear-$T$ contribution below 30 K, attributed to the two-dimensional (2D) spin-wave mediated electron-electron interactions in antiferromagnets. At higher temperatures (40–160 K), the conductivity $\sigma \propto b{T}^{1/3}$, with coefficient $b$ scaling with disorder strength $k_F{l}_0$ and the exchange interaction $J$, is consistent with the 3D incipient Anderson localization theories in the presence of dominant electron-magnon scattering. Moreover, the electron-magnon scattering time ${\tau }_{\mathrm{in}}$ was estimated based on the 2D to 3D dimensional crossover observed at about 40 K, which is consistent with theoretical results using the formula predicted by Muttalib et al. [Phys. Rev. B 91, 144410 (2015)]. Our work elucidates the critical role of electron-magnon interactions in modulating the incipient Anderson localization and thus influencing the quantum transport properties of disordered magnetic materials.

We introduce a topologically distinct skyrmion, termed a spin-flux skyrmion, which shares the same real-space magnetization profile as a conventional skyrmion but differs fundamentally in its underlying topological structure. This distinction originates from the path traced by its rotation matrices within the doubly connected SO(3) group manifold, leading to a nontrivial spinor phase of $e^{i\pi }$ upon encircling the texture. Using an explicit SU(2) gauge field formalism, we derive the emergent magnetic field components generated by both conventional and spin-flux skyrmions. While conventional skyrmions exhibit a dominant ${\sigma }_z$ component with weak dipolar ${\sigma }_x,{\sigma }_y$ contributions, spin-flux skyrmions possess an additional monopolar ${\sigma }_x$ component that yields a finite average emergent field for a finite density of skyrmions. This nontrivial component introduces a nontrivial term in the Hall conductivity, enabling a direct explanation of experimental Hall resistivity anomalies that cannot be accounted for by conventional skyrmions alone. Moreover, we show that this additional term couples to the in-plane spin polarization of conduction electrons, providing a further tunable handle to control the transverse Hall response.