Intercalated compounds offer a versatile platform for high-temperature superconductivity, as exemplified by sodium-intercalated graphite ($\mathrm{Na}{\mathrm{C}}_8$) with a transition temperature ($T_{\mathrm{c}}$) above 28 K. However, the microscopic origins of their structural robustness and superconducting behavior remain elusive. Here we establish a unified framework integrating stacking geometry, intercalated-cation chemistry, bonding topology, and pressure tuning to uncover the mechanisms governing stability and superconductivity. Through extensive first-principles investigations of 36 designed B-N compounds intercalated with $s$-, $p$-, and early $d$-block cations, we propose an electrogeometric stabilization mechanism in which structural robustness arises from the cooperative balance between optimal charge donation filling bonding σ states and geometric compatibility with the interlayer spacing. This balance enhances lattice rigidity and regulates electron-phonon coupling and band dispersion, thereby governing the superconducting behavior. Notably, the $R\text{−}3m$ phase of $\mathrm{Na}{\mathrm{B}}_2{\mathrm{N}}_2$ exhibits a predicted $T_{\mathrm{c}}$ of $\sim 40.6\mathrm{K}$; evolutionary searches further indicate its feasible synthesis. These findings establish fundamental design principles for realizing high-$T_{\mathrm{c}}$ superconductivity in intercalated materials.

An array of quantum dots coupled via superconductivity provides a new platform for creating Kitaev chains with Majorana zero modes, offering a promising avenue toward topological quantum computing. In this work, we theoretically study the quantum capacitance of a minimal Kitaev chain weakly coupled to an external normal lead. We find that, in the open regime, charge stability diagrams of quantum capcaitance can help to identify the sweet spot of a Kitaev chain, consistent with tunnel spectroscopy. Moreover, the quantum capacitance of a single quantum dot coupled to Andreev bound states reveals the interplay between two distinct parity switching mechanisms: coupling to an external normal lead and intrinsic quasiparticle poisoning. Our work provides useful physical insights into the quantum capacitance and parity dynamics in a quantum-dot-based Kitaev chain device.

The superconductor/ferromagnet/superconductor (S/F/S) Josephson junctions (JJs) with an anomalous ground state phase shift ${\phi }_0\ne 0,\pi$ $({\phi }_0\text{−}\mathrm{S}/\mathrm{F}/\mathrm{S} \mathrm{JJs})$ enable the implementation of the zero-field Josephson diode effect with the possibility to control the diode efficiency and polarity. It is just as important that in this case ${\phi }_0$ provides a coupling between the superconducting phase and the magnetization of the interlayer. Such ${\phi }_0\text{−}\mathrm{S}/\mathrm{F}/\mathrm{S} \mathrm{JJs}$ can be used for superconducting memory and logic circuit applications. Here we present the results of theoretical calculation of the current-phase relationship (CPR), exhibiting the Josephson diode effect and ${\phi }_0\ne 0,\pi$, for a JJ through a specific magnetic material. As the interlayer of the JJ we consider an ultrathin film of intermetallic lanthanide $\left(Ln\right)$-based compound ${\mathrm{GdIr}}_2{\mathrm{Si}}_2$. Using the density functional theory (DFT) methods, we study the electronic structure and magnetic properties of the film. Then the effective tight-binding Hamiltonian (TBH), demonstrating high quantitative consistency with the electronic properties obtained from DFT calculations, is constructed. The TBH is used to calculate CPR in the framework of the Bogoliubov–de Gennes approach. The CPRs demonstrate a pronounced ${\phi }_0$ of the order of unity and a pronounced Josephson diode effect with the diode efficiency $\lesssim 0.3$. Moreover, the efficiency can be controlled via rotation of in-plane magnetization in the interlayer. The prospects for utilizing alternative magnetic $Ln$-based materials of the $Ln{T}_2{X}_2$ family ($T$ is a transition metal and $X$ is a $p$ element from groups III–V) for the implementation in ${\phi }_0\text{−}\mathrm{S}/\mathrm{F}/\mathrm{S} \mathrm{JJs}$ are also discussed.

We present a comprehensive first-principles study of twisted bilayer graphene (tBLG) for a wide range of twist angles, with a focus on structural and electronic properties. By employing density functional theory (DFT) with an optimized local basis set, we simulate tBLG, obtaining fully relaxed commensurate structures for twist angles down to 0.987°. For all angles, the lattice relaxation agrees well with continuum elastic models. For angles accessible to plane-wave DFT (vasp), we provide a detailed comparison with our local basis DFT (siesta) calculations, demonstrating excellent agreement in both the atomic and electronic structures. The dependence of the Fermi velocity and band width on the twist angle shows qualitative agreement with results from an ‘‘exact’’ $\mathbf{k}·\mathbf{p}$ continuum model, but reveals a small twist angle offset. Additionally, we provide details of the low-energy wave-function character, band inversion and symmetries. Our results provide an ab initio reference point for the microscopic structure and electronic properties of tBLG, which will serve as the foundation for future studies incorporating many-body effects.

We report the carrier-density dependence of the magnetotransport property in the correlated Dirac semimetal ${\mathrm{CaIrO}}_3$. In the dilute carrier density region ($n_{\mathrm{H}} \sim 2.2\times {10}^{16}{\mathrm{cm}}^{-3}$) at $2\mathrm{K}$, the mobility exceeds $1.0\times {10}^5{\mathrm{cm}}^2/\mathrm{Vs}$ at $2\mathrm{K}$, and the transverse magnetoresistance reaches $2000\%$ at $12\mathrm{T}$. The analysis of quantum oscillations and Hall conductivity shows that the Fermi velocity is nearly independent of the cross-sectional area of the Fermi surface, or equivalently the carrier density, supporting a $k$-linear dispersion of the Dirac node. The field dependence of magnetoresistivity is nearly $B$-linear in the moderate carrier density region ($n_{\mathrm{H}}\ge 4\times {10}^{16}{\mathrm{cm}}^{-3}$), but scales with $B^{\alpha }$ ($\alpha >2$) in the lower carrier density region. The variation of magnetoresistivity is likely affected by the enhanced long-range Coulomb interaction in the quantum limit, where Dirac electrons are subject to the magnetic confinement.

We report the realization and modeling of a triple-antidot molecule hosting three interacting quantum Hall quasiparticles, with tunnel coupling between antidots tunable via the magnetic field. The measured tunneling conductance spectrum reveals the molecular energy levels arising from the interantidot coupling and Coulomb interaction. A tunneling model is established, which shows good qualitative agreement with experimental observations. In this work, we lay the foundation for the realization of complex systems of antidots for quantum Hall quasiparticles with nontrivial quantum statistics.

Anisotropic photonic time crystals (APTCs), enabled by periodic temporal modulation of a uniform anisotropic medium, exhibit asymmetric momentum-band gap structures and offer unique control over light–matter interactions. Here, we introduce and construct temporal Weyl points (TWPs) in APTCs within a synthetic three-dimensional space defined by two phase parameters and the quasifrequency. The temporal response reveals robust Fermi arcs linking TWPs of opposite topological charge. Unlike spatial counterparts, these Fermi arcs emerge only after the first temporal supercell comprising multiple periods of APTCs, reflecting causality. We further show that TWPs enable tunable emission from stationary charges embedded in APTCs, while the associated Fermi arcs robustly suppress radiation at selected directions and frequencies. Our findings establish temporal Weyl physics in photonic time crystals and uncover new opportunities for topological control of light–matter interactions through the time dimension.

We propose a method for calculating exciton spectra and wave functions for model lattice Hamiltonians, based on real-space electron-hole propagators. We verify that our results agree with those of the continuum approximation in the limit of large Wannier excitons, and propose a simple criterion to estimate the exciton size above which the continuum approximation is quantitatively accurate. We then investigate simple one- and two-dimensional multiorbital lattice models and show that small, Frenkel-like excitons, whose size approaches the lattice constant, can display physics that disagrees with the simplest continuum descriptions (a single-valley quadratic expansion around the minimum gap) not just quantitatively, but qualitatively. Specifically, we identify sharp transitions in the character and momentum of the lowest-energy exciton, enabled by the multiorbital nature of the lattice models.

We investigate high-Chern-number quantum anomalous Hall (QAH) phases in sliding bilayer hexagonal lattices. Lateral displacement between layers acts as a symmetry-reduction mechanism that breaks $C_3$ rotational symmetry and shifts band crossings to generic momenta in the Brillouin zone. When time-reversal symmetry is broken by Haldane-type complex next-nearest-neighbor hoppings, these crossings are gapped, yielding insulating phases with Chern numbers up to $\left|C\right|=4$. The large topological charge arises from asymmetric interlayer hybridization mediated by skew hopping channels, which enable multiple inequivalent band inversions within the four-band manifold and redistribute the Berry curvature. Ribbon calculations confirm the corresponding number of chiral edge modes. Our results establish sliding-controlled interlayer hybridization as a symmetry-driven route to nonadditive high-Chern QAH phases in bilayer systems.

From a symmetry perspective, ferroaxial order belongs to the same symmetry as time-reversal-even pseudovectors. Experimentally, ${\mathrm{K}}_2\mathrm{Zr}{\left({\mathrm{PO}}_4\right)}_2$ is known to undergo a displacive-type phase transition from a nonferroaxial to a ferroaxial phase. To identify the key microscopic ingredients driving this transition, we carry out a quantitative analysis combining density-functional theory calculations and symmetry-adapted closest Wannier analysis. As a result, we show that electric toroidal dipole, electric toroidal octupole, and electric hexadecapole, which belong to the same irreducible representation, make dominant contributions to the ferroaxial transition. In particular, we find that spinless electric toroidal octupoles, which originate from spin-independent off-diagonal real hopping between the $p$ orbitals on P and O atoms and between the $d$ orbitals on Zr atoms and $p$ orbitals on O atoms, provide the most significant contributions. Moreover, we explicitly analyze the orbital characters involved in the relevant hybridizations associated with these multipoles. We further show that the relativistic spin-orbit coupling has a negligible influence on the ferroaxial transition. These results demonstrate that spin-independent orbital hybridization between different orbitals on different atoms plays a crucial role in inducing the ferroaxial transition.

Manifolds with nontrivial topology play an essential role in the study of topological phases of matter. In this paper, we study the nontrivial symmetry response of the (2+1)-dimensional $Z_2$ symmetry-protected topological (SPT) phase when the system is put on a nonorientable manifold: the Klein bottle. In particular, we find that when a symmetry defect is inserted along the orientation-reversing cycle of the Klein bottle, the ground state of the system gets an extra charge. This response remains well defined at transition points into the trivial SPT phase, resulting in an exact twofold degeneracy in the ground state independent of the system size. We demonstrate the symmetry response using exactly solvable lattice models of the SPT phase, as well as numerical work across the transition. We explore the connection of this result to the modular transformation of the (3+1)-dimensional $Z_2$ gauge theory and the emergent nature of the parity symmetry in the $Z_2$ SPT phase.

Thermoelectric (TE) materials enable sustainable bidirectional conversion between heat and electricity, facilitating waste heat recovery and cooling. However, optimizing their performance is challenging due to the intertwined and often competing nature of electronic and thermal transport properties. Although high-throughput screening accelerates discovery, computational costs often limit simultaneous accuracy in both electronic and thermal predictions. Here, we develop a first-principles framework that incorporates key scattering mechanisms for both electrons and phonons and solves the Boltzmann transport equation to compute electronic and lattice thermal transport properties. This approach enables efficient and accurate evaluation of 1136 semiconductors, compiled into an interactive database. Herein, we identify promising TE candidates with band gaps between 0 and 0.8 eV, allowing effective Fermi level tuning. Experimental synthesis of one candidate ScPtSb confirms excellent TE performance, validating our predictive approach. In this work, we provide a robust computational resource and guidance for accelerated development of high-performance TE materials.

We compute and analyze the dependence of excitonic second- and third-harmonic generation (SHG/THG) as a function of the optical excitation intensity in the presence of static electric fields by solving the semiconductor Bloch equations. Our simulations are performed for excitation of the strongly bound intralayer exciton of an inversion-symmetric homobilayer of ${\mathrm{MoS}}_2$ with in-plane electric fields. We demonstrate that for resonant excitation at the $1s$ K-exciton the SHG and the THG show complex dependencies on both the strength of the static field and the peak amplitude of the optical pulse. For sufficiently intense optical excitation, the THG increases and the SHG increases superlinearly with the amplitude of the static field as long as exciton ionization is not yet dominating. Microscopic simulations demonstrate that these dependencies arise from an interplay between several effects including static and transient Stark shifts, exciton ionization, off-resonant Rabi oscillations, and a modified interference between optical nonlinearities induced by the intraband acceleration. Our findings offer several new possibilities for controlling the strong-field dynamics of systems with strongly bound excitons.

Topological phase transitions in photonic systems are traditionally realized by geometrically modifying the unit cell. Here, we introduce a cavity-based mechanism that enables dynamic control of topological phases without structural alterations. Specifically, we study the topological phase of electric dipolar arrays placed between two parallel metal plates. Using the image-charge method, we demonstrate that the coupling strength between dipoles is strongly influenced not only by their distances to the two plates but also by the orientation of the dipoles themselves. Exploiting this feature, we construct an equally spaced Su-Schrieffer-Heeger (SSH) chain composed of dipoles with tailored orientations. We show that when the chain is closer (farther) to the top plate than to the bottom plate, the system exhibits a topologically trivial (nontrivial) phase. Hence, the topological phase of the array can be controlled simply by tuning the relative position of the chain between the two plates. We further generalize this approach to two-dimensional dipolar arrays, demonstrating its applicability to a Kagome lattice. This cavity-enabled strategy offers a practical route for achieving topological phase transitions in photonic systems without the need for lattice geometry modification, paving the way for more versatile implementations of topological photonics.

The emergence of altermagnets offers a promising platform for studying spin-charge coupling scenarios. In this study, we investigate the significant regulatory influence of uniaxial strain on the electronic and plasmonic properties of two-dimensional $d$-wave altermagnets, specifically, monolayer ${\text{V}}_2{\text{Se}}_2\text{O}$. Our analysis, based on density functional theory calculations and a tight-binding model of an altermagnetic Lieb lattice, reveals that applying strain along the [100] direction effectively lifts the degeneracy between the X and Y valleys, enabling the generation of spin-polarized carriers at optimal hole-doping concentrations. Compressive strain along the [100] direction promotes directional propagation of spin plasmons along the $x$ direction, whereas tensile strain shifts this behavior to the $y$ direction. Moreover, applying tensile strain along the [110] direction retains the $d$-wave altermagnetic characteristics while resulting in distinct anisotropic responses in spin plasmons that diverge from those induced by [100] strain. The observation of low-loss spin plasmons and their strain-tunable propagation in monolayer ${\text{V}}_2{\text{Se}}_2\text{O}$ greatly enhance the application potential of spin plasmons and pave the way for exploration of mechanical-electric and mechanical-optical couplings in altermagnetic materials.

We present a unified machine-learning-based framework to investigate the electronic structure and plasmonic response of graphene/hexagonal boron nitride (hBN) moiré heterostructures. This framework integrates machine-learning-derived interatomic potentials and a data-driven Hamiltonian model, facilitating a fully ab initio-trained and parameter-free strategy that effectively links atomic relaxation processes to electronic property predictions. By applying this methodology, we conduct a systematic exploration of the graphene/hBN moiré heterostructures at four representative twist angles, revealing distinct out-of-plane corrugations in the relaxed structures predicted by the machine-learned potential. Our findings uncover a twist-angle-dependent reduction in the Dirac-point gap within the electronic bands. Additionally, the calculated plasmon spectra exhibit pronounced electron-hole asymmetry due to the presence of the secondary Dirac-point gap, consistent with previous theoretical expectations. Importantly, our approach eliminates the necessity for empirical parameter fitting, thus enhancing its applicability to a broader range of two-dimensional heterostructures with complex interlayer geometries. This work paves the way for a generalized framework that enables automated, high-accuracy modeling of moiré systems, effectively integrating ab initio data, machine learning, and the study of collective excitations.

Two-dimensional van der Waals (vdW) ferroelectric $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$, renowned for its structural adaptability and electrically switchable polarization, presents a transformative platform for advanced nanoelectronics. Here, employing first-principles calculations based on density functional theory, we systematically explore the pressure-modulated electronic states of twisted $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ moiré superlattices, including conventional stacking configurations constructed from ferroelectric $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ quintuple layers. In contrast to the conventional stackings, key findings are revealed in twisted $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ moiré superlattices: First, interlayer twist engineering induces localized interfacial charge states and generates flat electronic bands near the Fermi level, suggesting potential emergence of correlated quantum phases. Second, externally applied out-of-plane pressure drives a spatial redistribution of interfacial charges toward intralayer regions, accompanied by progressive band gap closure and a reversible semiconductor-to-metal transition, demonstrating robust mechano-electronic coupling. Third, strategic introduction of surface selenium vacancies amplifies the system's responsiveness to mechanical stimuli, accelerating band gap closure under pressure through localized strain and defect-mediated charge reorganization. These results establish a unified framework linking twist engineering, ferroelectrics, and defect control in vdW heterostructures and offer unprecedented avenues for designing adaptive nanoelectronics, including mechanically reconfigurable devices and strain-engineered quantum platforms.

We study the degree of band flatness and anisotropic quantum geometry in magic-angle twisted bilayer graphene by varying the twist angle and the lattice relaxation through optical conductivity. We show that the degree of band flatness and its quantum geometry can be revealed through optical absorption and its resulting optical bounds, which are based on the trace condition in quantum geometry. More specifically, the narrow and isolated peak of optical absorption in the low-energy region provides information about the bandwidth between two flat bands. When this value is smaller than the electron interaction, it serves as a critical condition for the emergence of flat-band superconductivity. Furthermore, optical absorption also provides the gap value between the flat band and the dispersive band, and when this gap is larger than the electron interaction, it facilitates the realization of fractional Chern insulating phases. We show that the narrow and isolated peak of optical bound near zero energy decreases as lattice relaxation increases. Meanwhile, we demonstrate that the imaginary part of generalized optical Hall conductivity reveals the vanishing of the negative part of Berry curvature, which is enforced by the refined trace-determinant inequality. Accordingly, we show that the total amount of the negative part and component of the Berry curvature approaches zero in the single ideal flat-band case. In contrast, when considering all occupied bands, the total amount of the negative component is slightly different from zero. Finally, we demonstrate that the condition of vanishing of flat-band velocities and the emergent chiral symmetry are sufficient for the saturation of the trace condition, which pertains to the isotropic case. In contrast, the determinant condition can be saturated in anisotropic systems, and the quantum metric and Berry curvature are related by a “saturation matrix” whose elements can be measured through the optical response. Additionally, the nonvanishing difference between the optical bound and the imaginary part of the generalized optical Hall conductivity also provides an anisotropic signature in the fractional Chern insulating phases.