Hexagonal boron nitride (hBN) flakes are key building blocks for encapsulating two-dimensional (2D) materials, providing atomically flat surfaces and an excellent dielectric environment for high-mobility field-effect transistors and tunneling devices. However, strain induced during mechanical exfoliation and assembly of van der Waals heterostructures may lead to plastic deformations of the hBN surface, injecting dislocation lines between the topmost layer and the underlying film. Since a monolayer of hBN is noncentrosymmetric and exhibits a piezoelectric response to deformation, individual dislocations and, in particular their networks, can generate electrostatic-potential modulations in the encapsulated 2D material. Here, we examine scenarios in which the top hBN layer is uniaxially strained and/or twisted, and show how lattice reconstruction into dislocation networks leads to the formation of piezoelectric-charge hotspots that effectively behave as charged defects.

Two-dimensional Fermi liquids at low temperatures have been theoretically established to exhibit an odd-even effect in the collective quasiparticle relaxation rates where even-parity deformations of the Fermi surface decay at a much faster rate than odd-parity ones. A predicted consequence of this effect is a new tomographic transport regime that mixes hydrodynamic and collisionless transport. In the presence of a magnetic field, however, the tomographic regime is expected to evolve towards conventional transport regimes as soon as the cyclotron radius becomes smaller than the dominant odd-parity mean-free path. In this work, we examine this transition from the point of view of collective modes, using a numerically exact solution of the linearized Boltzmann equation within a generalized relaxation time approximation for the odd-parity and even-parity modes. In the absence of a magnetic field, the transverse conductivity exhibits two diffusive tomographic collective modes, and we find that at a critical magnetic field one of these two tomographic modes disappears. Which tomographic mode persists depends on the Landau parameters, and becomes increasingly dominated by hydrodynamic modes at high fields. We corroborate our analysis using a variational approach for the Fermi surface deformation that captures the angular structure of the deformation and the critical magnetic field strength. The collective modes discussed here can in principle be observed by examining the damping of longitudinal and transverse current responses in finite magnetic fields.

Lithium carbide (${\mathrm{Li}}_2{\mathrm{C}}_2$), a potential electrode material for lithium ion batteries, has recently gained attention as a promising tritium breeding material for magnetic confinement fusion reactor owing to its higher breeding ratio compared to conventional ternary ceramics. Motivated by the reported pressure-induced $Immm\to Pnma$ structural phase transition in ${\mathrm{Li}}_2{\mathrm{C}}_2$ [I. Efthimiopoulos et al., Phys. Rev. B 92, 064111 (2015)], previously we had investigated pressure dependence of structural, dynamical, electronic, and mechanical properties of these two phases. However, for prospective applications in fusion reactors and energy-storage technologies, a comprehensive understanding of its thermal response under extreme thermodynamic conditions is essential. In this work, we present a comprehensive ab initio investigation of the thermophysical behavior of the aforementioned phases over a wide range of temperatures (0–900 K) and hydrostatic pressures (0–25 GPa). Various thermodynamic quantities including thermal expansion coefficient, isothermal and adiabatic bulk moduli, isochoric and isobaric heat capacities, Debye temperature, and ion thermal conductivity are systematically evaluated. The findings highlight significant changes in the thermal response among two allotropes of ${\mathrm{Li}}_2{\mathrm{C}}_2$. A unique class of exponential functions is proposed to describe the temperature dependence of thermophysical parameters for both phases of ${\mathrm{Li}}_2{\mathrm{C}}_2$. Additionally, the pressure dependence of all studied thermophysical parameters is found to conform to a generalized power-law relationship. Study enabled estimating shock Hugoniot parameters, a prerequisite for understanding dynamic response of a material. The volume dependence of Grüneisen parameter is determined and compared with analytical models proposed by Slater, Dugdale and MacDonald, Vaschenko and Zubarev, and scaling law of Meyers. Study reveals that the Vaschenko-Zubarev model and scaling law follow closely with ab initio results, whereas others deviate significantly. The compression-dependent Grüneisen parameter is then utilized to predict melting curve of this compound. Finally, study is extended to construct high-temperature high-pressure equation of state of ${\mathrm{Li}}_2{\mathrm{C}}_2$. This comprehensive analysis provides valuable insights into the behavior of ${\mathrm{Li}}_2{\mathrm{C}}_2$ under different thermodynamic conditions, and supports its potential application as a tritium breeding material in fusion energy systems.

Current-induced spin-orbit torque has emerged as a powerful technique for manipulating magnetization switching of ferromagnet/nonmagnet (FM/NM) based memory cell. By investigating nonequilibrium spin torque effect in a van der Waals heterobilayer, trigonal ${\mathrm{Cr}}_3{\mathrm{Te}}_4/{\mathrm{PtTe}}_2$, the first-principles quantum transport calculations are applied to determine both local spin induction, resulting from Rashba-Edelstein effect in the FM layer, and spin current injection, flowing from the NM to the FM layer. Our work reveals that local spin induction significantly generates the fieldlike torque, which primarily governs the switching current in systems with strong in-plane magnetic anisotropy. Our work emphasizes the importance of optimizing spin Hall effect in the NM layer for perpendicular magnetic anisotropy (PMA)-based magnetization switching and maximizing the Rashba effect in the FM layer for in-plane magnetic anisotropy (IMA)-based switching.

We report a dynamic magnetostrictive effect in type-II superconductors (e.g., Nb, ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7\text{−}x}$, ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$ and ${\mathrm{Ba}}_{0.6}{\mathrm{K}}_{0.4}{\mathrm{Fe}}_2{\mathrm{As}}_2$) and any type-II superconductor is expected to present a similar response to this new technique. Measured via a composite magnetoelectric technique, an ac field excites an in-phase, nondissipative strain response scaling linearly with vortex density in the vortex lattice phase. In the vortex liquid phase, the signal acquires an out-of-phase component before vanishing in the normal state. We propose the ac strain susceptibility a thermodynamic criterion for the vortex lattice, capturing vortex collective modes inaccessible from static measurements.

The Remeika stannides ($R_3{\mathrm{T}}_4{\mathrm{Sn}}_{13}$, with R = rare earth/alkaline metals, T = transition metal, and X = p-block elements) have been extensively studied due to the interplay between the charge-density-wave (CDW) ordering and superconductivity often found in these materials. Here, we explore the relationship between these two orders in cubic ${\mathrm{La}}_3{\mathrm{Co}}_4{\mathrm{Sn}}_{13}$ by conducting electrical transport measurements under uniaxial stress along different crystallographic directions ([100], [110], and [111]). We find that the superconducting transition temperature $\left(T_{\mathrm{c}}\right)$ is suppressed under compression for all directions measured, in contrast to previous measurements under hydrostatic pressure. This indicates $s$-wave superconductivity. The CDW transition temperature is also suppressed under compression for all measured directions. The simultaneous suppression of superconductivity and CDW order suggests that changes in $T_{\mathrm{c}}$ with uniaxial stress are mainly driven by changes in the electronic density of states and not a competition between these two orders.

We investigated the effects of Ni doping on carrier density and anomalous electrical transport properties in ${\mathrm{CeCo}}_{1-x}{\mathrm{Ni}}_x{\mathrm{In}}_5$ $(x\le 0.3)$ by performing Hall resistivity measurements. The carrier density, estimated from the Hall coefficient $R_{\mathrm{H}}$ at a temperature of 0.5 K in high magnetic fields, increases linearly with $x$, indicating that the doped Ni ions act as electron dopants. In ${\mathrm{CeCoIn}}_5$, the magnitude of $-R_{\mathrm{H}}$ is strongly enhanced at magnetic fields near the superconducting upper critical field $H_{c2}$ and in the low-field region above the superconducting transition temperature $T_c$. However, these anomalies are found to be significantly suppressed by Ni doping. Possible origins of this suppression in $-R_{\mathrm{H}}$ are discussed.

As a powerful theoretical construct, the entanglement Hamiltonian (EH) encapsulates the essential entanglement properties of a quantum many-body system. From the EH, one can extract a variety of entanglement quantities, such as entanglement entropies, negativity, and the entanglement spectrum. However, its general analytical form remains largely unknown. While the Bisognano-Wichmann theorem gives an exact EH form for Lorentz-invariant field theories, its validity on lattice systems is limited, especially when Lorentz invariance is absent. In this work, we propose a general scheme based on the lattice-Bisognano-Wichmann (LBW) ansatz and multi-replica-trick quantum Monte Carlo methods to numerically reconstruct the entanglement Hamiltonian in two-dimensional systems and systematically explore its applicability to systems without translational invariance, going beyond the scope of the original Bisognano-Wichmann theorem. Various quantum phases—including gapped and gapless phases, critical points, and phases with either discrete or continuous symmetry breaking—are investigated, demonstrating the versatility of our method in reconstructing entanglement Hamiltonians. Furthermore, we find that when the entanglement boundary of a system is ordinary (i.e., free from surface anomalies), the LBW ansatz provides an accurate approximation well beyond Lorentz-invariant cases. Our work thus establishes a general framework for investigating the analytical structure of entanglement in the complex quantum many-body systems.

The quantum metric, the real part of a quantum geometric tensor, plays an important role in fundamental transport and optical responses of quantum materials. While net quantum metric effects are typically realized by breaking both time-reversal ($\mathcal{T}$) and inversion ($\mathcal{P}$) symmetries, valley-contrast mechanisms enable the probing of quantum geometry in centrosymmetric, nonmagnetic systems, revealing physical signatures beyond Berry curvature. Here, we design a four-layer ${\mathrm{MoS}}_2$ platform that combines sliding antiferroelectric order with strain-induced $C_{3z}$ breaking to realize a quantum metric driven nonlinear valley Hall effect (NVHE) under preserved $\mathcal{P}$ and $\mathcal{T}$ symmetries. Reversible interlayer sliding ($\mathrm{ABBA}\leftrightarrow \mathrm{BAAB}$) provides nonvolatile electrical control of the valley response. First-principles calculations reveal an outer-layer-dominated NVHE with tunable sign and magnitude. This symmetry-preserving, sliding-tunable strategy activates hidden quantum geometric phenomena in realistic two-dimensional materials and opens a clean pathway for tunable valleytronics and quantum information devices.

The Berry curvature, akin to the magnetic field in reciprocal space, provides an intriguing avenue for exploring unique electromagnetic phenomena devoid of real-space analogs. In this work we investigate reciprocal-space electromagnetic induction, including the contributions from time-varying Berry curvature and the magnetic charge current in topological semimetals, where a nodal line and Weyl nodes coexist under a driving term. We find that the Berry curvature along the nodal loop is nonuniform: it aligns with the azimuthal direction on one half of the loop, while on the other half, it points antiparallel. Moreover, as the Weyl node moves in reciprocal space, its monopole charge can change sign. As a result, the average emergent electric field passing through the nodal loop or the Weyl point's motion orbit does not consistently align with its normal direction. Instead, one half of the field is parallel to the normal, while the other half is antiparallel. In both cases the total emergent electric field in reciprocal space sums to zero. However, by connecting the topological semimetal to an electrode, we can detect the electric field with a nonzero local average through the quantum pumping effect. Our research sheds light on different types of electromagnetic induction effect, thus broadening our comprehension of electromagnetic phenomena.

Self-interaction error (SIE) is a well-known limitation of standard density functional theory (DFT), yet its significance for single-atom catalysts (SACs) remains largely overlooked. Here we show that correcting SIE via $\mathrm{DFT}+U$ is not merely a methodological refinement but a prerequisite for reliably predicting the electronic structure and catalytic activity of $3d$ metal-${\mathrm{N}}_4$ SACs, especially for near-half-filled $d$-shell systems (Mn, Fe, Co, Ni). These SACs exhibit pronounced $U$-sensitivity, manifesting as $d$-level shifting and spin-state transitions driven by the interplay between on-site Coulomb repulsion and the quasi-$D_{4h}$ ligand field. Crucially, this sensitivity translates directly to catalysis. Using the oxygen reduction reaction as a model reaction, we find that $\mathrm{DFT}+U$, in agreement with experiments, successfully predicts $\mathrm{Fe}\text{−}{\mathrm{N}}_4$ to be the more active catalyst than $\mathrm{Co}\text{−}{\mathrm{N}}_4$, whereas standard DFT fails. This reversal originates from a downshift of occupied $d$ orbitals that weakens hybridization with ${}^{*}\mathrm{OOH}$ and ${}^{*}\mathrm{OH}$. Interestingly, for ${\mathrm{Fe}}^{*}\mathrm{O}, {\mathrm{Co}}^{*}\mathrm{O}$, and ${\mathrm{Mn}}^{*}\mathrm{OH}$, a spin-state transition partially offsets this weakening via Hund's exchange, leading to a less pronounced decrease in adsorption energy. These findings establish that SIE correction is essential for reliable SAC modeling, particularly for near-half-filled $d$-shell systems, and our work provides a mechanistic framework to understand its impact on catalytic predictions.

While charge density waves (CDWs) are a hallmark of the kagome metal $\mathrm{Cs}{\mathrm{V}}_3{\mathrm{Sb}}_5$, their absence in the bilayer counterpart $\mathrm{Cs}{\mathrm{V}}_6{\mathrm{Sb}}_6$ remains a notable exception, with the underlying mechanism yet to be elucidated. Here, integrating ultrafast spectroscopy with first-principles calculations, we demonstrate that the lack of charge orderings in $\mathrm{Cs}{\mathrm{V}}_6{\mathrm{Sb}}_6$ originates from a synergy between an altered electronic structure and fundamentally weakened electron-lattice coupling. Experimentally, coherent phonon dynamics exhibit purely conventional anharmonic behavior without CDW-associated anomalies, while electron dynamics reveal a markedly reduced electron-phonon coupling strength (i.e., 0.13 in $\mathrm{Cs}{\mathrm{V}}_6{\mathrm{Sb}}_6$ versus 0.88 in $\mathrm{Cs}{\mathrm{V}}_3{\mathrm{Sb}}_5$). Consistent with these experimental observations, first-principles calculations indicate an absence of Fermi-surface nesting and a shift of Van Hove singularities away from the Fermi level in $\mathrm{Cs}{\mathrm{V}}_6{\mathrm{Sb}}_6$. Together, our results establish a unified physical picture in which suppressed electronic instabilities and weak lattice coupling preclude CDW formation in bilayer kagome metals.

Motivated by recent developments in the study of quasi-one-dimensional iron systems with ${\mathrm{Fe}}^{2+}$, we comprehensively study an ${\mathrm{Fe}}^{3+}$ chalcogenide chain system. Based on first-principles calculations, the ${\mathrm{Fe}}^{3+}$ chain has a similar electronic structure to that discussed before for the ${\mathrm{Fe}}^{2+}$ chain, because of the similar $\mathrm{Fe}{X}_4$ ($X=\mathrm{S}$ or Se) tetrahedron-chain geometry. Furthermore, a three-orbital electronic Hubbard model for this chain was constructed using the density matrix renormalization group method. A robust antiferromagnetic coupling was unveiled in the chain direction. In addition, in the intermediate electronic correlation $U/W$ region, we found an interesting orbital-selective Mott phase with the coexistence of localized and itinerant electrons ($U$ is the on-site Hubbard repulsion, while $W$ is the electronic bandwidth) based on the orbital-selective behavior observed in the charge fluctuations. Furthermore, we do not observe any obvious pairing tendency in the ${\mathrm{Fe}}^{3+}$ chain in the electronic-correlation $U/W$ region, where superconducting pairing tendencies were reported before in iron ladders. This suggests that superconductivity is unlikely to emerge in the ${\mathrm{Fe}}^{3+}$ systems. Our results clearly establish the similarities and differences between ${\mathrm{Fe}}^{2+}$and ${\mathrm{Fe}}^{3+}$ iron chains, as well as iron ladders.

We develop a systematic theory of spectral decimation for quantum many-body Hamiltonians and show that it provides a quantitative probe of emergent symmetries in statistically mixed spectra. Building on an analytical description of statistical mixtures, we derive an explicit expression for the size of a characteristic symmetry sector (CSS), defined as the largest subsequence of levels exhibiting non-Poissonian correlations. The CSS dimension is shown to be the size-biased average of the underlying symmetry sectors, establishing a direct link between spectral statistics and Hilbert-space structure. We apply this framework to two paradigmatic settings: Hilbert-space fragmentation and disorder-induced many-body localization. In fragmented systems, the CSS reproduces the mixture prediction and isolates correlated subsectors even when the full spectrum appears nearly Poissonian. In the disordered Heisenberg chain, spectral decimation reveals the gradual emergence of integrability through a shrinking CSS, whose statistics exhibit signatures consistent with local integrals of motion. We introduce a characteristic symmetry entropy as a finite-size scaling observable and extract, within accessible system sizes, the crossover exponents. Our results establish spectral decimation as a controlled, unbiased, and computationally inexpensive diagnostic of hidden structure in many-body spectra, capable of distinguishing between chaotic dynamics, statistical mixtures, and emergent integrability.

We studied the electronic structure of multilayer indium films grown on Si(111) using angle-resolved photoelectron spectroscopy. Quantum well state (QWS) bands derived from In $5sp$ electrons were observed in the energy range of 0–3.4 eV, and their thickness-dependent energy shifts were well reproduced by the phase accumulation model. In addition, multiple bands with small energy spacings of $\sim 0.1\mathrm{eV}$ were observed near the Si valence-band maximum. These states originate from the coupling between the In $5sp$ states and the quantized heavy-hole (HH) states in the space-charge layer of $n$-doped Si(111). With increasing thickness, the HH-like states shifted to lower energies, while a new higher-energy state emerged when they energetically overlapped with a QWS. This repeated reorganization of the HH-like states is attributed to the thickness-dependent phase shift of the In $5sp$-derived component at the In/Si interface. Furthermore, this phase shift is found to be closely related to the preferred growth of the 9-ML and 13-ML indium films.

We develop a general theory for twisted bilayer photonic crystals that takes into account both far-field response and near-field coupling. The theory is based on the framework of a generalized Rayleigh-Schrödinger perturbation theory for non-Hermitian Hamiltonians. A universal form for interlayer coupling is derived, which relates the hopping strength to the Fourier transforms of the Wannier functions in the single layer photonic crystal. For low-energy states at the K point in hexagonal lattices, the interlayer coupling reduces to that in the Bistritzer-MacDonald model for graphene. As an example, we study a twisted bilayer photonic crystal slab with air holes arranged in a honeycomb lattice in each layer. The first-order solution of our model predicts a fourfold band splitting in the far-field spectrum compared to the single-layer case, which is confirmed by numerical simulations. Moreover, our theory reveals that for low-energy states at K points, scattering toward the $\mathrm{\Gamma }$ point via the moiré potential is suppressed. Based on our theory, we propose a wide-angle, high-$Q$ tunable flat band cavity by combining the bilayer at a large twist angle with a Brillouin-zone-folding perturbation within each layer. The cavity behaves like a collection of quasibound states in the continuum with a divergent density of states, with potential applications in nonlinear optics, lasing, and quantum optics.

Recently, proximity-induced spin-orbit coupling (SOC) has been observed in heterostructures consisting of monolayer graphene (ML-G) and transition metal dichalcogenides (TMDCs), such as ${\mathrm{WSe}}_2$. Successful tuning of SOC in graphene/${\mathrm{WSe}}_2$ heterostructures by applying mechanical pressure and electric fields was also demonstrated in previous studies. In addition, theoretical calculations predicted a strong dependence of the proximity-induced SOC on the twist angle between graphene and TMDC. Here, we put these predictions to experimental test in $\mathrm{ML}\text{−}\mathrm{G}/\mathrm{ML}\text{−}{\mathrm{WSe}}_2/\mathrm{hBN}$-heterostructures, where the twist angle is determined by aligning fractured edges, and by crystallographic etching of graphene. By performing weak anti-localization measurements, we determine the strength of the Rasbha-type SOC (${\lambda }_{\mathrm{R}}$) and the valley-Zeeman-type SOC (${\lambda }_{\mathrm{VZ}}$). Our experiments confirm a strong twist-angle dependence of the proximity-induced SOC in agreement with theoretical predictions. Finally, we demonstrate the tunability of the SOC strength via mechanical pressure, which is in agreement with earlier findings.

We investigate the mechanical and vibrational properties of three quasiplanar two-dimensional (2D) monolayers (${\mathrm{Be}}_2\mathrm{C}, {\mathrm{Be}}_5{\mathrm{C}}_2$, and ${\mathrm{B}}_4{\mathrm{C}}_3$) containing hypercoordinate carbon centers. Density functional theory was employed to determine the elastic response, Young's modulus, Poisson's ratio, and dynamical stability. ${\mathrm{B}}_4{\mathrm{C}}_3$ exhibits the highest in-plane stiffness ($\sim 249\mathrm{N}/\mathrm{m}$), nearly isotropic elasticity, and large cohesive energy, consistent with high mechanical resilience. ${\mathrm{Be}}_5{\mathrm{C}}_2$ displays strong elastic anisotropy and a negative Poisson's ratio ($\nu =-0.36$), indicative of auxetic behavior. ${\mathrm{Be}}_2\mathrm{C}$ shows intermediate stiffness and moderate flexibility. Phonon dispersions confirm that all three monolayers are dynamically stable. Electron localization function and crystal orbital Hamilton population analyses reveal extensive multicenter σ networks complemented by modest π delocalization ($\sim 10–15\%$), which facilitates uniform stress redistribution under deformation. These findings connect the topology of multicenter bonding with macroscopic elastic response, offering design guidelines for lightweight and flexible 2D materials.