We analyze, using first-principles calculations and the method of invariants, the spin-orbit proximity effects in trilayer heterostructures comprising phosphorene and encapsulating ${\mathrm{WSe}}_2$ monolayers. We focus on four different configurations, in which the top/bottom ${\mathrm{WSe}}_2$ monolayer is twisted by 0 or 60 degrees with respect to phosphorene and analyze the spin-splitting of phosphorene hole bands around the $\mathrm{\Gamma }$ point. Our results show that the spin texture of phosphorene hole bands can be dramatically modified by different encapsulations of phosphorene monolayer. For a symmetrically encapsulated phosphorene, the momentum-dependent spin-orbit field has the out-of-plane component only, simulating the spin texture of phosphorenelike group-IV monochalcogenide ferroelectrics. Furthermore, we reveal that the direction of the out-of-plane spin-orbit field can be controlled by switching the twist angle from 0 to 60 degrees. Finally, we show that the spin texture in asymmetrically encapsulated phosphorene has the dominant in-plane component of the spin-orbit field, comparable to the Rashba effect in phosphorene with an applied sizable external electric field. Our results confirm that the significant modification and control of the spin texture is possible in low common-symmetry heterostructures, paving the way for using different substrates to modify spin properties in materials important for spintronics.

Construction of two-dimensional van der Waals (vdW) heterostructure has been well recognized to provide an avenue towards designing functional optoelectronic and photovoltaic devices. Here, a type-II vdW heterostructure consisting of anisotropic black phosphorus (BP) and ${\mathrm{TiS}}_3$ possessing ultrafast interlayer charge transfer for photoconversion is established using ab initio nonadiabatic molecular dynamics with HSE06 hybrid functional. The present results demonstrate that the ultrafast interlayer electron and hole transfer occur within 42 and 467 fs, respectively, which is mainly ascribed to the electron-phonon coupling dominantly contributed by an interlayer breathing mode and the stretching mode of ${\mathrm{TiS}}_3$ induced by in-plane vibration of interfacial S-S pairs. Moreover, it is discovered that the interlayer charge transfer process can be effectively controlled by the external electric field (EEF); i.e., positive (negative) EEF can sustain (slow down) the ultrafast carrier dynamics and facilitate (degenerate) the separation of electron and hole. The present findings pave the way to developing high-performance functional optoelectronic devices based on two-dimensional vdW heterostructure.

We generate compact localized states (CLSs) in an electrical diamond lattice, comprised of only capacitors and inductors, via local driving near its flat-band frequency. We compare experimental results to numerical simulations and find very good agreement. We also examine the stub lattice, which features a flat band of a different class where neighboring compact localized states share lattice sites. We find that local driving, while exciting the lattice at that flat-band frequency, is unable to isolate a single compact localized state due to their nonorthogonality. Finally, we introduce lattice nonlinearity and showcase the realization of nonlinear compact localized states in the diamond lattice. We induce an instability in the nonlinear CLS when it is shifted into resonance with a dispersive (optical) band. Our findings pave the way of applying flat-band physics to complex electric circuit dynamics.

The emergence of negative differential friction (NDF) in two-dimensional (2D) layered materials, which does not obey the classical Da Vinci–Amontons law of friction, has attracted much attention in recent years. Although there has been a great deal of study on NDF, a universal understanding for its appearance in 2D materials remains lacking. Here, we try to give general insights from the common existence of interlayer quasibonding (QB) interaction in 2D materials, which is usually a repulsion interaction for some typical 2D materials. Based on density-functional theory calculations, we study the friction of four homobilayers of 2D materials ($H$- and $R$-stacking $\mathrm{Mo}{\mathrm{S}}_2, h$-BN, and graphene) with increasing load. The interlayer QB repulsion becomes stronger as the normal load increases, which is beneficial to the appearance of NDF. The appearance of NDF can be attributed to the competition of (1) the relative rapid increase in the interlayer repulsion (which is correlated to interlayer QB) and (2) the relatively slow increase of the interlayer London dispersion attraction of van der Waals interaction. Further analysis manifests that the magnitude of the interlayer QB-induced splitting of energy bands is related to NDF, and then we provide a quantitative analysis of interlayer bonding strength to support this view. Since QB exists commonly in 2D layered materials, our insights are general and inspire perspectives on tuning the interlayer friction.

We analyze dynamical transport properties of a hybrid nanostructure, comprising a correlated quantum dot embedded between the source and drain electrodes, which are subject to an ac voltage, focusing on signatures imprinted on the charge transport by the side-attached Majorana zero-energy mode. The considerations are based on the Kubo formula, for which the relevant correlation functions are determined by using the numerical renormalization group approach, which allows us to consider the correlation effects due to the Coulomb repulsion and their interplay with the Majorana mode in a nonperturbative manner. We point out universal features of the dynamical conductance, showing up in the Kondo-Majorana regime, and differentiate them against the conventional Kondo and Majorana systems. In particular, we predict that the Majorana quasiparticles give rise to universal fractional values of the ac conductance in the well-defined frequency range below the peak at the Kondo scale. We also show this Kondo scale to actually increase with strengthening the coupling to the topological superconducting wire.

The Weyl-Mott insulator (WMI) has been postulated as a novel type of correlated insulator with nontrivial topological properties. We introduce a minimal microscopic model that captures generic features of the WMI transition in Weyl semimetals. The model hosts a bulk Mott insulator with spinon Fermi arcs on its surfaces which we identify as a WMI, i.e., a $U\left(1\right)$ Weyl quantum spin liquid. At finite temperatures, we find an intermediate Weyl semimetallic phase with no quasiparticles which is consistent with the bad semimetallic behavior observed in pyrochlore iridates, $A_2{\mathrm{Ir}}_2{\mathrm{O}}_7$, close to the Mott transition. Spinon Fermi arcs lead to a suppression of the bulk Mott gap at the surface of the WMI, in contrast to the gap enhancement expected in conventional Mott insulators, which can be detected through angular resolved photoemission spectroscopy.

We derive Lorentz-invariant four-fermion interactions, including Nambu-Jona-Lasinio type and superconducting type, which are widely studied in high-energy physics, from the honeycomb lattice Hamiltonian with Hubbard interaction. We investigate the phase transitions induced by these two interactions and consider the effects of the chemical potential and magnetic flux (Haldane mass term) on these phase transitions. We find that the charge density wave and superconductivity generated by the attractive interactions are mainly controlled by the chemical potential, while the magnetic flux delimits the domain of phase transition. Our analysis underscores the influence of the initial topological state on the phase transitions, a facet largely overlooked in prior studies. We present experimental protocols using cold atoms to verify our theoretical results.

We demonstrate that the topological charge associated with nontrivial phononic Weyl points may be interchanged between nonadjacent locations within the Brillouin zone of a strained crystal. This occurs in our NiMnSb test case upon passing between tensile and compressive uniaxial strain through the higher-symmetry unstrained geometry, and compensates for what would otherwise appear to be nonconservation of topological charge. The phenomenon is dictated by the material's crystallographic point group, and should be replicated in other crystals of similar symmetry.

Lattice models with supersymmetry are known to exhibit a variety of remarkable properties that do not exist in the relativistic models. In this paper, we introduce an interacting generalization of the Kitaev chain of Majorana fermions with $\mathcal{N}=1$ supersymmetry and investigate its low-energy properties, paying particular attention to the ground-state degeneracy and low-lying fermionic excitations. First, we establish the existence of a phase with spontaneously broken supersymmetry and a phase transition out of it with the help of variational arguments and the exact ground state. We then develop, based on the superfield formalism, a simple mean-field theory, in which the order parameters detect supersymmetry breaking, to understand the ground-state phases and low-lying Nambu-Goldstone fermions. At the solvable point (frustration-free point), the exact ground state of an open chain exhibits large degeneracy of the order of the system size, which is attributed to the existence of a zero-energy domain wall (dubbed kink or skink) separating the topological and trivial states of Majorana fermions. Our results may shed new light on the intriguing ground-state properties of supersymmetric lattice models.

Materials with ferroelectrically switchable topological properties are of interest for both fundamental physics and practical applications. Using first-principles calculations, we find that stacking ferroelectric $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ monolayers into a bilayer leads to polarization-dependent band structures, which yields polarization-dependent topological properties. Specifically, we find that the states with interlayer ferroelectric couplings are quantum spin Hall insulators, while those with antiferroelectric polarizations are normal insulators. We further find that ${\mathrm{In}}_2{\mathrm{Se}}_3$ trilayer and quadlayer exhibit nontrivial band topology as long as in the structure the ferroelectric ${\mathrm{In}}_2{\mathrm{Se}}_3$ bilayer is antiferroelectrically coupled to ${\mathrm{In}}_2{\mathrm{Se}}_3$ monolayers or other ferroelectric ${\mathrm{In}}_2{\mathrm{Se}}_3$ bilayer. Otherwise the system is topologically trivial. The reason is that near the Fermi level the band structure of the ferroelectric ${\mathrm{In}}_2{\mathrm{Se}}_3$ bilayer has to be maintained for the nontrivial band topology. This feature can be used to design nontrivial band topology for the thicker films by a proper combination of the interlayer polarization couplings. The topological properties can be ferroelectrically tunable using the dipole locking effect. Our study reveals switchable band topology in a family of natural ferroelectrics, which provide a platform for designing new functional devices.

Several long-debated dynamical and elastic unusual properties of $\delta$-Pu are captured within a unified theoretical framework. This outcome is achieved owing to machine learning accelerated ab initio simulations enabling a fine description of strong electronic correlations and explicit temperature effects. First, the experimental negative thermal expansion and equilibrium volume of pure $\delta$-Pu are correctly depicted. Second, the extreme softening of the phonon spectrum, related to huge anharmonic effects, is demonstrated to be responsible for the anomalous decrease of the bulk modulus with temperature, as measured experimentally. Lastly, our model successfully reproduces experimental elastic properties of alloyed $\delta$-Pu between $T=100$ and $800\mathrm{K}$.

In superconductors, the condensation of Cooper pairs gives rise to fluxoid quantization in discrete units of ${\mathrm{\Phi }}_0=hc/2e$. The denominator of $2e$ is the signature of electron pairing, which is evidenced by a number of macroscopic quantum phenomena, such as the Little-Parks effect and the Josephson effect, where the critical temperature or the critical current oscillates with the periodicity of ${\mathrm{\Phi }}_0$. Here we report the observation of Little-Parks oscillation periodicities of $2{\mathrm{\Phi }}_0$, $3{\mathrm{\Phi }}_0$, and $4{\mathrm{\Phi }}_0$, besides the conventional ${\mathrm{\Phi }}_0$, in mesoscopic rings of epitaxial $\beta -{\mathrm{Bi}}_2\mathrm{Pd}$, a topological superconductor. These unexpected findings suggest new physics to account for the observed quantizations.

At optimal doping, different cuprate compounds can exhibit vastly different critical temperatures for superconductivity ($T_c$), ranging from about 20 to about 135 K. The precise properties of the lattice that determine the magnitude of the $T_c$ are currently unknown. In this paper, we investigate the dependence of the optimal doping $T_c$ on the parameters of the Emery ($d\text{−}p$) model for the ${\mathrm{CuO}}_2$ planes in the cuprates. We show that the best scaling is obtained not with the parameters of the model written in the real ($d/p$-orbital) space but rather written in the space of effective Wannier orbitals. In this basis, one obtains a model of three sublattices coupled through all possible four-point interactions. We identify multiple predictor variables that fit the experimental $T_c$ to about $\pm 4–5\mathrm{K}$ and that remarkably depend on the leading attractive coupling constants in the transformed Hamiltonian.

We consider phase-biased Josephson junctions with spin-orbit coupling under external magnetic fields and study the emergence of the Josephson diode effect in the presence of Majorana bound states. We show that junctions having middle regions with Zeeman fields along the spin-orbit axis develop a low-energy Andreev spectrum that is asymmetric with respect to the superconducting phase difference $\varphi =\pi$, which is strongly influenced by Majorana bound states in the topological phase. This asymmetric Andreev spectrum gives rise to anomalous current-phase curves and critical currents that are different for positive and negative supercurrents, thus signaling the emergence of the Josephson diode effect. While this effect exists even in the trivial phase, it gets enhanced in the topological phase due to the spatial nonlocality of Majorana bound states. Our paper thus establishes the utilization of topological superconductivity for enhancing the functionalities of Josephson diodes.

The quantum anomalous Hall state with a large band gap and a high Chern number is significant for practical applications in spintronics. By performing first-principles calculations, we investigate electronic properties of the fully fluorinated $1T\text{−}{\mathrm{MoSe}}_2$ monolayer. Without considering the spin-orbit coupling, the band structure demonstrates single-spin semimetallic properties and the trigonal warping around $K_{\pm }$ valleys. The introduction of the spin-orbit coupling opens considerable band gaps of 117.2 meV around the two valleys, leading to a nontrivial quantum anomalous Hall state with a Chern number of $\left|C\right|=2$, which provides two chiral dissipationless transport channels from topological edge states and associated quantized anomalous Hall conductivity. In addition, an effective model is constructed to describe the low-energy physics of the monolayer. Our findings in the ${\mathrm{MoSe}}_2{\mathrm{F}}_2$ monolayer shed light on large-gap quantum anomalous Hall states in two-dimensional materials with the chemical functionalization, and provide opportunities to design low-power and noise-tolerant spintronic devices.

We investigate the magnetic and electronic properties of strongly correlated perovskite ${\left({\mathrm{SrIrO}}_3\right)}_1/{\left({\mathrm{NdNiO}}_3\right)}_3$ superlattice by density-functional theory calculations. The semiconducting ground state of the superlattice adopts a metal-insulator transition (MIT) under compressive epitaxial strain. This MIT is induced by the large reduction of breathing distortion and octahedra antiferrodistortive distortion in the superlattice compared to the ${\mathrm{NdNiO}}_3$ under epitaxial strain. Furthermore, it is found that this breathing distortion couples to the T-type antiferromagnetic ordering with two types of magnetic order on Ni sublattices, leading to a magnetic state without the degenerate switched magnetic direction when the breathing distortion is unchanged. Our results provide a mechanism of MIT in superlattice and a possible way to tune the magnetic order by breathing distortion.

We consider spin-1/2 chains with external driving that breaks the continuous symmetries of the Hamiltonian. We introduce a family of models described by the Lindblad equation with local jump operators. The models have hidden strong symmetries in the form of quasilocal charges, leading to multiple nonequilibrium steady states. We compute them exactly in the form of matrix-product operators and argue that they are the analogues of quantum many-body scars in the Lindbladian setting. We observe that the dynamics leads to the emergence of a Gibbs ensemble constructed from the hidden charges.

The exploration of new pathways to achieve superconductivity in materials has always been a central focus of research in condensed matter physics. Skutterudites have garnered attention due to their intriguing physical properties and broad range of applications. In this study, we propose that rotating the planar ${\mathrm{P}}_4$ units within skutterudites is a viable method to induce superconductivity. The predicted compound, referred to as skutterudite-like ${\mathrm{CeP}}_3$, exhibits phonon-mediated superconductivity at ambient pressure. This phenomenon arises from the interaction between Ce/P-derived phonons and the Ce $4f$ and P $3p$ electrons. The energy barrier for transitioning from the skutterudite-like ${\mathrm{CeP}}_3$ to the conventional skutterudite-type ${\mathrm{CeP}}_3$ is as high as 1.53 eV/atom, indicating a substantial irreversibility. Additional calculations reveal that skutterudite-like ${\mathrm{CeP}}_3$ becomes thermodynamically stable at 25 GPa in the binary Ce-P phase diagram. Consequently, the skutterudite-like ${\mathrm{CeP}}_3$ can be synthesized by initially compressing the most stable bulk binary CeP and P at 25 GPa, followed by decompression. This work represents a significant step forward in the design of superconducting skutterudite-like compounds.