We report the thermodynamic and magnetotransport properties of the half-Heusler antimonide ErPdSb, studied on single-crystalline samples in wide ranges of temperature and magnetic fields. The compound was found to order antiferromagnetically at 1.2 K. In the paramagnetic state, it shows semimetallic behavior with a broad hump in the temperature-dependent electrical resistivity around 70 K. The results of ab initio calculations of the electronic structure of ErPdSb indicated a bulk insulating nature. In small magnetic fields the magnetoresistance is driven by a weak antilocalization effect, while in strong fields it is negative and describable by the de Gennes–Friedel formalism. The Hall effect data indicated that holes are the dominant charge carriers. At 2 K, the Hall conductivity exhibits a sizable anomalous contribution, which is obscured by multiband effects at higher temperatures. The angular magnetoresistance shows unusual features as functions of magnetic field and temperature, pointing to a possible field-induced reconstruction of the Fermi surface.

We derive a renormalized classical spin (RCS) theory for $S>1/2$ quantum magnets by constraining a generalized classical theory that includes all multipolar fluctuations to a reduced ${\mathrm{CP}}^1$ phase space of dipolar SU(2) coherent states. When the spin Hamiltonian $\widehat{\mathcal{H}}\left(S\right)$ is linear in the spin operators ${\widehat{\mathit{S}}}_j$ for each lattice site $j$, the RCS Hamiltonian ${\tilde{\mathcal{H}}}_{\mathrm{cl}}$ coincides with the usual classical model ${\mathcal{H}}_{\mathrm{cl}}={lim}_{S\to \infty }\widehat{\mathcal{H}}\left(S\right)$. In the presence of nonlinear terms, however, the RCS theory is more accurate than ${\mathcal{H}}_{\mathrm{cl}}$. For the many materials modeled by spin Hamiltonians with (nonlinear) single-ion anisotropy terms, the use of the RCS theory is essential to accurately model phase diagrams and to extract the correct Hamiltonian parameters from neutron-scattering data.

We introduce a new type of supercurrent valve based on full-shell nanowires. These hybrid wires consist of a semiconductor core fully wrapped in a thin superconductor shell and subjected to an axial magnetic field. Due to the tubular shape of the shell, the superconductor phase acquires an integer number $n$ of $2\pi$ twists or fluxoids that increases in steps with applied flux. By connecting two such hybrid wires, forming a Josephson junction (JJ), a flux-modulated supercurrent develops. If the two superconducting sections of the JJ have different radii $R_1$ and $R_2$, they can develop equal or different fluxoid numbers $n_1,n_2$ depending on the field. If $n_1\ne n_2$, the supercurrent is blocked, while it remains finite for $n_1=n_2$. This gives rise to a fluxoid valve effect controlled by the applied magnetic field or a gate voltage at the junction. We define a fluxoid-valve quality factor that is perfect for cylindrically symmetric systems and decreases as this symmetry is reduced. We further discuss the role of Majorana zero modes at the junction when the full shell nanowires are in the topological superconducting regime.

We study the quantum entanglement and quantum phase transition of the non-Hermitian anisotropic spin-$\frac{1}{2}$ XY model and XXZ model with the staggered imaginary field by analytical methods and numerical exact diagonalization, respectively. Various entanglement measures, including concurrence, negativity, mutual information, and quantum coherence, and both biorthogonal and self-normal quantities are investigated. Both the biorthogonal and self-normal entanglement quantities, except the biorthogonal concurrence, are found to be capable of detecting the first-order and $\mathcal{PT}$ transitions in the XXZ model, as well as the Ising and $\mathcal{RT}$ transitions in the XY model. In addition, we introduce the unconstrained concurrence and demonstrate its effectiveness in detecting these transitions. On the other hand, the Berezinskii-Kosterlitz-Thouless (BKT) transition in the XXZ model is revealed through concurrence and negativity at small non-Hermiticity strengths. Notably, the critical points observed in the Hermitian limit evolve into exceptional points as the strength of the non-Hermiticity increases. Furthermore, we find that the first-order transition survives up to a higher non-Hermiticity strength compared to the BKT transition within the $\mathcal{PT}$-symmetric regime of the XXZ model.

We study a dimerized spin-1/2 chain, such as ${\mathrm{CuGeO}}_3$, hosting triplon excitations coupled to optical phonons under weak terahertz laser driving. Both phonons and triplons weakly lose energy into the surrounding baths, forming a nonequilibrium steady state. In the strong phonon-triplon coupling regime, phonons near the two-triplon continuum hybridize strongly with triplons. Using mean-field Lindblad dynamics, we show that strong hybridization induces sharp first-order phase transitions—either single or simultaneous double—in the emission spectrum, mainly due to nonlinearities in the chain and the instantaneous breaking of spatial inversion symmetry, as captured by the phonon displacement. Using mean-field Floquet analysis of harmonic modes in both sectors, we analytically confirm the existence of these phase transitions. Furthermore, we map the complete steady-state phase diagram by varying key control parameters and provide experimentally relevant parameters for observing these transitions in laser-driven ${\mathrm{CuGeO}}_3$.

We consider superconductivity and pair density waves (PDWs) arising from off-site pairing in frustrated lattice geometries. We express the pair susceptibility in a generic form that highlights the importance of both the density of states, and the quantum geometry of the eigenstates and calculate the superfluid weight (stiffness) as well as the Berezinskii-Kosterlitz-Thouless temperature. Paradigmatic bipartite (Lieb) and nonbipartite (kagome) lattices are studied as examples. For bipartite lattices, nearest-neighbor pairing vanishes in a flat band. In the Lieb lattice flat band, we find a PDW at a finite interaction and show that its pair wave vector is determined by the quantum geometry of the band. In the kagome flat band, nearest-neighbor pairing is possible for infinitesimal interactions. At the kagome van Hove singularity, the pair susceptibility predicts a PDW due to sublattice interference, however, we find that its stiffness is zero due to the shape of the Fermi surface. Our results indicate that nearest-neighbor pairing at flat-band and van Hove singularities is strongly influenced by the geometric properties of the eigenfunctions, and it is crucial to determine the superfluid weight of the superconducting and PDW orders as it may contradict the predictions by pairing susceptibility.

Ternary transition-metal germanide superconductors with nonsymmorphic symmetries offer promising platforms for symmetry-protected topological phases. In this work, we investigate ZrIrGe, which crystallizes in the nonsymmorphic TiNiSi-type structure. Electrical, magnetic, and specific heat measurements confirm bulk type-II superconductivity with a full gap and a transition temperature of 2.84(7) K, consistent with weak-coupling BCS behavior. First-principles calculations reveal hourglass-shaped bulk band dispersions and a Dirac chain composed of symmetry-protected fourfold-degenerate Dirac points, leading to drumheadlike surface states near the Fermi level. Additionally, ZrIrGe exhibits a nontrivial ${\mathbb{Z}}_2$ topological character, resulting in helical surface states that cross the Fermi level, making it a strong candidate for proximity-induced topological superconductivity. The coexistence of conventional superconductivity and topological band features establishes ZrIrGe as a rare stoichiometric system for exploring intrinsic topological superconductivity.

Many-body localization is a profound phase of matter affecting the entire spectrum which emer ges in the presence of disorder in interacting many-body systems. Recently, the stability of many-body localization has been challenged by the avalanche mechanism, in which a small thermal region can spread, destabilizing localization and leading to global thermalization of the system. A key unresolved question is the critical competition between the thermal region's influence and the disorder strength required to trigger such an avalanche. Here, we numerically investigate many-body localization stability in an isolated Heisenberg spin chain of size $L$ subjected to a disordered magnetic field. By embedding a tunable thermal region of size $P$, we analyze the system's behavior in both static and dynamical regimes using entanglement entropy and the gap ratio. Our study yields two main findings. Firstly, for strong disorder, the avalanche only occurs if the thermal region scales with system size, specifically when $P/L$ exceeds a threshold value. Secondly, at strong disorder, we identify an intermediate phase between many-body localization and ergodic behavior as $P$ increases. This intermediate phase leaves its fingerprint in both static and dynamic properties of the system and tends to vanish in the thermodynamic limit. Although our simulations are restricted to finite system sizes, the analysis suggests that these results hold in the thermodynamic limit for isolated many-body systems.

Kagome lattice materials have attracted significant research interest due to their unique electronic structures and emergent quantum phenomena. Three-dimensional kagome systems have been extensively investigated, while the exploration of two-dimensional (2D) kagome materials remains relatively limited, presenting both scientific challenges and opportunities. In this work, through systematic first-principles calculations, $M{\mathrm{B}}_6$ ($M=\mathrm{In},\mathrm{Tl}$), featuring in bilayer kagome borophene, are predicted to exhibit remarkable phonon-mediated superconductivity. These two compounds display superconducting transition temperatures ($T_c$) of 7.0 and 5.0 K, respectively, which are nearly two orders of magnitude higher than the 0.03 K predicted in intrinsic bilayer kagome borophene. Our analysis reveals that the coupling between B-$p_z$, $M\text{−}{p}_x/p_y$ ($M=\mathrm{In},\mathrm{Tl}$) electrons and low-frequency phonons of metal atoms contributes greatly to their superconductivity. Notably, $M{\mathrm{B}}_6$ ($M=\mathrm{In},\mathrm{Tl}$) possess nontrivial band topology, suggesting the potential candidates for topological superconductivity. This work not only expands the family of 2D superconducting materials, but also provides a theoretical exploration for novel quantum phenomena in kagome systems.

At present, the research on two-dimensional (2D) piezoelectric photocatalysts for water splitting lacks relevant physical quantities to describe the time for the progress of photogenerated carriers to transport from the interior of the material to the surface and participate in the photocatalytic reaction under the built-in electric field. Herein, we proposed the quasihorizontal projectile motion model of carriers and then quantified the time (τ) for the photogenerated carriers to participate in the above process in a series of 2D piezoelectric photocatalyst Janus ${\mathrm{GeN}}_2$-XY monolayers through first-principles calculations. We found that the magnitude of τ in ${\mathrm{GeN}}_2$-XY is in the femtosecond range, which is much smaller than the recombination time of photogenerated carriers in most 2D semiconductors (which is in the picosecond or longer range). This means that the photogenerated carriers in ${\mathrm{GeN}}_2$-XY are likely to migrate to the material surfaces before recombination and participate in the photocatalytic reaction. This highlights the advantages of 2D piezoelectric photocatalysts. In addition, we propose the elasticity–bond order (BO) mechanism and the two-step strategy. The BO mechanism explains that the in-plane elastic stiffness coefficient of 2D materials increases with the bond-order sum of all the atomic bonds that contribute along the in-plane direction in the structure. This provides important inspiration for the design of 2D flexible wearable devices. And the two-step strategy provides a summary of the method for controlling the photocatalytic water splitting of 2D materials through piezoelectric effects clearly.

The light-matter interaction in optical cavities offers a promising ground to create hybrid states and manipulate material properties. In this work, we examine the effect of light-matter coupling in the excitonic insulator phase using a quasi-one-dimensional lattice model with two opposite parity orbitals at each site. We show that the model allows for a coupling between the collective phase mode and cavity photons. Our findings reveal that the collective mode of the excitonic state significantly impacts the dispersion of the cavity mode, giving rise to an avoided band crossing in the photon dispersion. This phenomenon is absent in trivial and topological insulator phases and also in phonon-mediated excitonic insulators, underscoring the unique characteristics of collective excitations in excitonic insulators. Our results demonstrate the significant impact of light-matter interaction on photon propagation in the presence of excitonic collective excitations.

Two-dimensional van der Waals (vdW) ferromagnets drive the advancement in spintronic applications and enable the exploration of exotic magnetism in low-dimensional systems. The entanglement of the dual—localized and itinerant—nature of electrons lies at the heart of the correlated electron systems giving rise to exotic ground state properties such as complex magnetism, heavy fermionic behavior, Kondo lattice formation, etc. Through temperature-dependent electronic structure of vdW ferromagnets, ${\left({\mathrm{Co}}_x{\mathrm{Fe}}_{1-x}\right)}_3{\mathrm{GeTe}}_2$, probed using high-resolution photoemission spectroscopy and density functional theory combined with dynamical mean field theory $(\mathrm{DFT}+\mathrm{DMFT})$, we provide direct evidence of the emergence of Kondo resonance peak driven by complex interplay between localized and itinerant electrons. In overall agreement with experimental electronic structure and magnetic properties, $\mathrm{DFT}+\mathrm{DMFT}$ also reveals finite spin band splitting well beyond $T_C$. Core levels, valence band photoemission spectra together with $\mathrm{DFT}+\mathrm{DMFT}$ spectral functions reveal insignificant change across $T_C$ indicating non-Stoner magnetism in ${\left({\mathrm{Co}}_x{\mathrm{Fe}}_{1-x}\right)}_3{\mathrm{GeTe}}_2$. Our results provide a way forward to the understanding of complex interplay between electronic structure, exotic magnetism, and heavy fermionic behavior leading to the Kondo scenario in $3d$ vdW ferromagnets.

Lattice Hamiltonians, which can be tuned between different topological phases, are known as important tools for understanding physical mechanism behind topological phase transitions. In this paper, we introduce a perturbed color code Hamiltonian with a rich phase structure, which can be well matched to the mechanism of anyon condensation in the color code. We consider a color code model defined on a three-colorable hexagonal lattice and add Ising interactions between spins corresponding to edges of the lattice. We show that Ising interactions play the role of physical factor for condensing anyons in the color code. In particular, corresponding to three different colors of edges in the hexagonal lattice, we consider three different coupling parameters. Then, we are able to condense anyons with different colors by tuning power of Ising interactions in the corresponding edges. In particular, we explicitly show that condensation of one type of anyons in the color code leads to a phase transition to the toric code state. On the other hand, by condensing two types of anyons, we observe a phase transition to a modified version of the toric code where partial set of anyons in the toric code are condensed and we call it a partially topological phase. Our main method for derivation of the above results is based on a suitable basis transformation on the main Hamiltonian in the sense that our model is mapped onto three decoupled transverse-field Ising models, corresponding to the three colors. We use the above mapping to analyze behavior of string order parameters as nonlocal indicators of topological order. We introduce three string order parameters that can well characterize different phases of the model. Specifically we give a simple description of the partially condensed phase by using string order parameters.

Exciton-polariton condensation occurs at the dispersion extrema, where the density of states diverges and polaritons can naturally accumulate. The existence of multiple such points leads to coupling and competition between the associated modes and dynamical redistribution of the polaritons in the dispersion. Here, we directly engineer the above situation via subwavelength periodic patterning of a two-dimensional nanostructure. This leads to multiple condensates that form at high-momenta, accidental-coupling points, and a high-symmetry $\mathrm{\Gamma }$ point with a bound-in-the-continuum state. The dynamical behavior of the system reveals the nonsimultaneous appearance of these condensates and the interplay of gain and relaxation mechanisms. We fully characterize the quasistatic and dynamical regime of this artificial crystal and the properties of the different condensates. This understanding is necessary when band-structure engineering techniques are used to achieve precise control of condensate formation with given energy and momentum.

Using first-principles self-consistent calculations, we show that ${\mathrm{MnSe}}_2$ with room-temperature ferromagnetism serves as a promising magnetic proximity partner for nonmagnetic ${\mathrm{MoS}}_2$ to realize a giant intrinsic anomalous Hall effect. The anomalous Hall conductivity (AHC) reaches up to ${10}^3$ S/cm, exceeding that of ${\mathrm{MnSe}}_2$ itself by over 30 times, and persists across a wide energy range spanning of 100 meV near the Fermi energy. This large AHC arises from the proximity-induced significant unbalance distribution of Berry curvature near multiple valleys (comprising two traditional valleys from ${\mathrm{MoS}}_2$ and six additional valleys from ${\mathrm{MnSe}}_2$), for which crystalline anisotropy plays a crucial role. We further illustrate that the giant intrinsic AHC remains robust to the changes in stacking configuration and vertical strain despite band modification. In addition, the significant AHC observed near the Fermi energy in ${\mathrm{MoS}}_2/{\mathrm{MnSe}}_2$ vanishes when ${\mathrm{MnSe}}_2$ is substituted with alternative magnets. Our results establish a routine for leveraging heterostructure anisotropy to design low-power Hall sensors or circuits based on ${\mathrm{MoS}}_2$.

Dirac semimetals can be classified into types I, II, and III based on the topological charge of their Dirac points. If a three-dimensional (3D) system can be sliced into a family of $k_z$-dependent normal and topological insulators, type I Dirac points separate a 2D normal insulator from a 2D first-order topological insulator, while type II (III) Dirac points separate a 2D normal (first-order) insulator from a 2D second-order topological insulator. To investigate the effects arising from the interplay of distinct Dirac points, one may wonder whether these Dirac points can coexist in a single system. Here, we propose a scheme to induce composite Dirac semimetals by a special Floquet driving that preserves time-reversal and space-inversion symmetries. A general description is established to characterize Dirac semimetals in Floquet systems. The results show that Dirac semimetals hosting coexisting type I, II, and III Dirac points can be induced by delta-function or harmonic driving. Our results provide a promising avenue for exploring novel Dirac semimetals.

The spin and integer quantum Hall effects are two cousins of topological phase transitions in two-dimensional electronic systems. Their close relationship makes it possible to convert spin to integer quantum Hall effect by continuous increase in a symmetry breaking Zeeman magnetic field. We study microscopic and mesoscopic peculiarities of bulk-edge correspondence and a fate of massless edge and bulk topological (instantons) excitations at such a crossover in topological superconductors. We propose possible experimental verification of our predictions.