In this work, we present a comprehensive first-principles study of liquid lead (Pb) properties at high temperatures, with emphasis on the near-critical region. Using ab initio molecular dynamics combined with density functional theory, we systematically investigate the thermodynamic properties of lead, including thermal expansion, enthalpy, isochoric and isobaric heat capacities, the Grüneisen parameter, and the speed of sound at expansions up to 45 times. Self-diffusion and dynamic viscosity coefficients along the critical isobar are also presented. Some analytical approximations are provided to facilitate practical applications. We provide equation-of-state data for liquid and fluid expanded lead, significantly advancing the understanding of its behavior in the region of parameters practically unattainable by theoretical and experimental methods. The critical point parameters are determined to be $T_c=5.46\pm 0.10$ kK, ${\rho }_c=1.8\pm 0.3 {\mathrm{g}/\mathrm{cm}}^3$, and $P_c=0.8\pm 0.2$ kbar, with a critical compressibility factor $Z_c=0.20\pm 0.06$. We confirm a sharp threefold drop in dynamic viscosity between 600 and 1500 K and reveal a slow decrease at temperatures of 1500–5400 K. These findings are of fundamental importance for condensed matter physics and can be applied for the design of power plants with lead coolant.

We investigate operator spreading in random quantum circuits with gates drawn from orthogonal- or symplectic-invariant ensembles, revealing several key distinctions from the well-studied unitary-invariant case. We find that the ensemble-averaged Pauli-string weights relax to a ternary-valued structure, instead of the binary structure of unitary-invariant circuits. For orthogonal- or symplectic-invariant circuits, the domain wall separating trivial and scrambled regions has a finite width even for Haar-random gates, whereas domain walls are sharp for Haar-distributed random unitary circuits. We further find a fundamental dichotomy between random circuits with two-qubit gates from the two disconnected components of the orthogonal group: While the butterfly velocity for the special orthogonal ensemble lies between zero and the Haar value, the negative-determinant sector exhibits a nonzero lower bound for any gate distribution. Moreover, for qudit size $q=2$, the butterfly velocity can exceed that of the Haar-random ensemble.

$\alpha \text{−}{\mathrm{MnO}}_2$ is an emerging material for electronic, optoelectronic, and energy applications, owing to its structural flexibility and defect-driven functionality. During synthesis of $\alpha \text{−}{\mathrm{MnO}}_2$, native oxygen vacancies readily form and are typically compensated by foreign dopants. A thorough understanding of intrinsic defects is therefore essential for enabling controlled extrinsic doping and optimizing material performance. Using a density functional approach, we investigate the structural, electronic, magnetic, and optical properties of the ground-state C2-type antiferromagnetic $\alpha \text{−}{\mathrm{MnO}}_2$ in the presence of native point defects, including interstitials, vacancies, and antisites. We compute their thermodynamic stability, incorporating electrostatic corrections to eliminate spurious long-range interactions. Mn interstitial $\left({\mathrm{Mn}}_{\text{i}}\right)$ and Mn antisite on an O site $\left({\mathrm{Mn}}_{\text{O}}\right)$ introduce shallow donor levels, whereas O vacancy $\left({\mathrm{V}}_{\text{O}}\right)$ exhibits amphoteric behavior and acts as compensating centers. The calculated defect formation energies reveal pronounced competition between donor- and acceptor-type native defects, leading to strong intrinsic defect compensation under both Mn-rich and O-rich growth conditions. The presence of defects significantly perturbs the electronic structure of $\alpha \text{−}{\mathrm{MnO}}_2$, introducing spin-polarized midgap states, while O interstitial $\left({\mathrm{O}}_{\text{i}}\right)$ preserves the host antiferromagnetic order. Mn vacancy $\left({\mathrm{V}}_{\text{Mn}}\right)$ remains ionized across the band gap and behaves as a shallow acceptor, suggesting its potential role under suitable nonequilibrium growth conditions, whereas O antisite on a Mn site $\left({\mathrm{O}}_{\text{Mn}}\right)$ forms deep acceptor levels. $\mathrm{BSE}@G_0{W}_0$ calculations reveal a strongly anisotropic optical response in stoichiometric $\alpha \text{−}{\mathrm{MnO}}_2$, while native point defects introduce pronounced sub-gap excitations and enhanced dielectric screening, with vacancies producing the largest effect.

${\mathrm{Co}}_2\mathrm{MnGa}$ is a ferromagnetic Weyl semimetal that may exhibit a giant anomalous Hall effect and negative longitudinal magnetoresistance (LMR), both of which originate from its band structure, giving rise to a large Berry curvature and a chiral anomaly. A previous positron annihilation study revealed that even in a highly ordered, stoichiometric bulk single crystal of ${\mathrm{Co}}_2\mathrm{MnGa}$, a large number of single vacancies are inevitably present. In the present work, density measurements indicated that the vacancy concentration could reach up to $\sim 1$ at. %, but a giant anomalous Hall conductivity (AHC) of $\gtrsim 1500$ S/cm was observed. Further analysis showed that the giant AHC is maintained by an intrinsic contribution of $\sim 1000$ S/cm, which is lower than the theoretical value for a perfect crystal (1500–2000 S/cm), along with an additional extrinsic contribution of $\sim 500$ S/cm, mainly caused by skew scattering. The ab initio calculation suggested that the electronic states along the Weyl nodal lines are not significantly altered, provided that only Ga vacancies are introduced. However, the Fermi level is shifted below the Weyl nodes, which decreases the intrinsic AHC. Negative LMR and its ${\cos }^2\theta$-like angular dependence were also observed. However, the major part of the LMR originates from the dynamics of magnetic domains under an applied magnetic field, whereas the chiral anomaly, if present, appears to have only a limited effect in the present condition.

Sensing number states of a magnonic mode has been accomplished using a superconducting qubit by realizing an effective dispersive interaction between the two systems. Here, we theoretically demonstrate that a seemingly classical bosonic mode can be utilized as a probe for resolving the number states of a magnon mode, while outperforming a qubit in various regards as the sensor. Considering another magnon mode in an antiferromagnet as the probe mode, we delineate the required dispersive coupling emerging directly from antiferromagnetic exchange interaction. When a phonon is used as the probe mode, we derive the effective dispersive coupling emerging from the lowest-order nonlinear magnon-phonon interactions. Our two considered examples provide the general design principles for identifying and utilizing a bosonic probe mode for sensing magnonic superpositions in a physical platform of interest.

Electron-electron correlations and electron-phonon coupling underlie a wide spectrum of quantum phenomena. Electrides are materials in which excess electrons localize in interstitial regions as non-nuclear attractors (NNAs), providing a unique platform to probe their interplay. In this study, using crystal structure prediction and first-principles calculations, we identify two lithium-rich electrides, $I4\text{/}mmm\text{−}\mathrm{L}{\mathrm{i}}_4\mathrm{Ir}$ and $R\overline{3}m\text{−}\mathrm{L}{\mathrm{i}}_8\mathrm{Ir}$. With respect to $\mathrm{L}{\mathrm{i}}_4\mathrm{Ir}$, pressure drives a remarkable evolution of ground states: a Stoner-type ferromagnet at 200 GPa is transformed into a stripe antiferromagnetic (sAFM) type above 252.8 GPa, which is ultimately transformed into a nonmagnetic metal at 450 GPa. The sAFM order results in a spin density wave that stems from the intrinsic instability of flat, NNA-derived bands under strong Coulomb repulsion, rather than Fermi surface nesting. The stability of this phase is improved by long-range electrostatic energy gains from charge redistribution. Notably, the metastable zigzag antiferromagnetic phase exhibits magnetoelastic coupling, inducing a symmetry-lowering structural distortion to the Pmmn space group. In nonmagnetic states, both $\mathrm{L}{\mathrm{i}}_4\mathrm{Ir}$ and $\mathrm{L}{\mathrm{i}}_8\mathrm{Ir}$ are predicted to host phonon-mediated superconductivity. While spin-orbit coupling has a minimal effect on the electronic structure of magnetic phases, it significantly modulates lattice dynamics and electron-phonon coupling by redistributing charge to the NNAs, thereby stabilizing superconductivity and suppressing dynamic instabilities. Our work demonstrates that lithium-rich Ir-based electrides constitute a tunable quantum material platform in which interstitial electrons govern unconventional magnetism, spin-lattice entanglement, and high-temperature superconductivity.

We investigate a two-leg ladder system subjected to an external magnetic field. In the absence of a magnetic field, the system is described by a clean tight-binding model, with no disorder in either the on-site potential or the hopping amplitudes. The effect of magnetic field in this system is studied by introducing the Peierls phases in the hopping amplitudes along a leg (appropriate when the Landau gauge is chosen). For a uniform magnetic field, characterized by a constant Peierls phase, we find that all eigenstates remain delocalized. In contrast, random Peierls phases, representing a random magnetic field, lead to complete localization of the eigenstates. We further show that a quasiperiodic modulation of the Peierls phase can drive a transition from a fully delocalized to a fully localized phase upon tuning the quasiperiodicity. For a two-parameter quasiperiodic Peierls phase, varying analogously to a generalized Aubry-André-type potential, we construct the phase diagram of the system. The phase diagram exhibits regions of delocalized and localized phases, separated by intermediate regimes of mixed phase. We also perform a semiclassical analysis that qualitatively yields a similar phase diagram, capturing the localization transition. Our results demonstrate a mechanism for controlling transport properties via the Peierls phase engineering.

We propose a minimal two-leg ladder model in which the mobility edge (ME) arises solely from bond modulation, induced by a slowly varying quasiperiodic modulation of the interleg tunneling amplitudes. We demonstrate that this bond-modulated ladder naturally hosts two propagation channels, whose symmetric and antisymmetric combinations experience opposite effective on-site potentials. Using the adiabatic (slowly varying) limit of the modulation, we derive an exact analytical condition for the single-particle mobility edge, $E_c=\pm |2t-\lambda |,$ where $t$ is the hopping amplitude along both legs and $\lambda$ is the bond modulation strength. This result directly generalizes the classic ME condition for slowly varying on-site potentials to a multileg (two-leg in our case) geometry. Extensive numerical calculations, including inverse participation ratios, Lyapunov exponents, density of states, and participation-ratio scaling, demonstrate excellent agreement with the analytical prediction across a wide range of parameters. We further identify a regime for small modulation exponents $0<\nu <1$, where localized and weakly delocalized states coexist even beyond the transition point $({\lambda }_c=2t)$. Finally, we characterize the crossover from the slowly varying regime to a true quasiperiodic regime where the adiabatic approximation breaks down, supported by a thorough scaling analysis of the generalized participation ratio and the multifractal properties of the eigenstates. Our results establish that a deterministic bond modulation can serve as a sufficient ingredient to produce an exact ME in ladder systems, offering experimentally accessible and advantageous routes toward tuning nonergodic extended phases.

Triangular-lattice systems attract a lot of attention due to various frustration-induced and strongly correlated effects. Here, we focus on the charge-ordering phenomenon by means of investigation of the extended Hubbard model with dynamical mean-field theory (DMFT). By considering the intersite nearest-neighbor interaction we have found a very rich phase diagram that contains a large number of features, phases, and phase transitions. Among them are site-selective Mott transitions; pinball-liquid (PL) phases where we distinguish charge-transfer-driven and Mott-localization-driven PLs; phase transitions that change their order as model parameters evolve (from discontinuous to continuous); very strong particle-hole asymmetry. Various features of the phase diagram are found to be better understood by means of the simple mean-field approximation (MFA). Moreover, besides helping with interpretation of the phase diagram, the MFA results together with results for the atomic-limit model are found to be able to set rather good expectations on how the DMFT phase diagram should look. Nevertheless, a few features were not expected and are found within the DMFT, such as a small-region intermediate metallic phase on an electron-doped side of the phase diagram.

Altermagnets represent a novel category of magnetic materials characterized by zero net magnetization yet featuring spin-split band structures, and they demonstrate distinctive orbital-spin locking phenomena. Commencing from the minimal multiorbital tight-binding Hamiltonian of $d$-wave altermagnets, we conduct an analysis of the general formulas for the third-order injection and shift currents. These currents are solely determined by the quantum metric and quantum connection, and involve no Berry curvature contribution. In the ideal scenario where the $\delta$-bond hopping $V_{\delta }$ approaches zero $(V_{\delta }=0)$, we derive closed-form analytical solutions for the third-order photoconductivities. For the general situation with a finite value of $V_{\delta }$, we present a perturbative analytical solution within the limit of $V_{\delta }\ll V_{\pi }$, and this solution is verified through numerical calculations. Our research establishes a comprehensive theoretical description of the third-order optospintronic responses in $d$-wave altermagnets based on a microscopic model. Moreover, it offers a viable approach for the experimental observation of pure quantum geometric effects.

Spin-active color centers are the basis of solid-state defect systems utilized in quantum technologies. Although silicon is an emerging host material for quantum defects, there is an urgent need to characterize color centers with a nonzero electron-spin ground state in this platform, in addition to the prominent T center. In this work, we perform first-principles calculations to identify the possible atomic structures compatible with the experimentally observed N-line series in silicon. We propose that the core structure of the N1 center consists of a neighboring carbon and nitrogen interstitial pair. Furthermore, we predict that more complex defects involving self-interstitial and interstitial oxygen atoms are feasible candidates for the further lines in the series. As all of these color centers are isoelectronic to the T center, they provide a family of alternative spin qubits with emission near the low-energy telecommunication bands.

We report on an investigation of quantum oscillations (QOs) in high field (up to 35 T) and low temperature (down to 0.5 K) in the samarium hexaboride Kondo insulator. Both high sensitivity ac-calorimetry and transport measurements have been used. We clearly observed QOs in a ${\mathrm{LaB}}_6$ single crystal used as a reference, but we did not observe any QOs in our high quality isotopically enriched ${}^{154}\mathrm{Sm}{}^{11}\mathrm{B}_6$ crystals, within our detection threshold (up to a few ${10}^5$ in specific heat at $\sim 1\mathrm{K}$, i.e., $\sim 0.05$ $\mathrm{pJ}/{\mathrm{K}}^2$). Our results rather support the hypothesis suggesting that defects in the Kondo lattice are creating metallic puddles [H. Pirie et al., Science 379, 1214 (2023)] which could be responsible for the QOs previously observed in ${\mathrm{SmB}}_6$.

The coexistence of Dirac points and van Hove singularities (VHSs) near the Fermi level provides a promising mechanism for realizing high-temperature superconductivity and nontrivial topology in 2D systems. Here, via global structural searches, we identify four stable Ta-S monolayers: ${\text{Ta}}_2{\text{S}}_3$, TaS, ${\text{Ta}}_3{\text{S}}_2$, and ${\text{Ta}}_2\text{S}$. All four phases exhibit superconductivity ($T_c$ of 3.091 K, 4.194 K, 5.799 K, and 3.731 K, respectively) driven by VHS-enhanced density of states and Dirac dispersions. Notably, in the three Ta-rich systems (TaS, ${\text{Ta}}_3{\text{S}}_2$, and ${\text{Ta}}_2\text{S}$) where $Ta\ge 50\%$, robust spin-orbit coupling induces a continuous band gap with a nontrivial $Z_2=1$ invariant. The internal coupling between superconductivity and topological edge states in these phases facilitates 1D topological superconductivity via the self-proximity effect, providing a versatile platform for exploring Majorana zero modes in 2D limit.

The electronic band structure of ${\mathrm{Na}}_2\mathrm{KSb}$ was studied by a combination of low-energy photoemission spectroscopy and density functional theory (DFT) calculations. The optical and photoemission quantum efficiency (QE) spectra, along with longitudinal energy distribution curves (EDCs) of multialkali ${\mathrm{Na}}_2\mathrm{KSb}(\mathrm{Cs},\mathrm{Sb})$ photocathodes were measured. The thresholds of various band-to-band transition in ${\mathrm{Na}}_2\mathrm{KSb}$ were observed in the optical and QE spectra of ${\mathrm{Na}}_2\mathrm{KSb}(\mathrm{Cs},\mathrm{Sb})$ photocathodes. The evolution of EDC derivatives with varying photon energy reveals a fine structure related to the emission of two types of electrons: (i) ballistic electrons, which are excited from heavy hole, light hole and split-off valence bands, and (ii) photoelectrons, that are captured in the side valleys of the ${\mathrm{Na}}_2\mathrm{KSb}$ conduction band. The analysis of EDCs and QE spectra allowed us to determine the band structure parameters of ${\mathrm{Na}}_2\mathrm{KSb}$ at $T=80\mathrm{K}$, including the band gap $E_{\text{g}}=1.53\pm 0.03\mathrm{eV}$, spin-orbit splitting ${\mathrm{\Delta }}_{\text{SO}}=0.59\pm 0.03\mathrm{eV}$, and the energy separations between $\mathrm{\Gamma }$ and X valleys of the conduction band: ${\mathrm{\Delta }}_{\mathrm{\Gamma }-\text{X}1}=0.41\pm 0.05\mathrm{eV}$ and ${\mathrm{\Delta }}_{\mathrm{\Gamma }-\text{X}2}=0.65\pm 0.05\mathrm{eV}$. The experimentally determined band gaps and side valley positions, as well as the energies of the final electronic states of optical transitions are in good agreement with the DFT calculations. The obtained data on the hot electron dynamics and electronic band structure of ${\mathrm{Na}}_2\mathrm{KSb}$ are crucial to improve the understanding of the photoemission processes in this material and will contribute to the development of the robust spin-polarized electron sources based on multialkali photocathodes.

In this paper, we examine the properties of spin-polarized interfaces consisting of single-molecule magnet bis(cyclopentadienyl)cobalt(II) (cobaltocene) and two-dimensional magnetic materials, semiconducting ${\mathrm{CrI}}_3$ and metallic ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$, using first-principles density functional theory based calculations. Our calculated adsorption energies indicate the stability of these heterointerfaces with the observation of hybridization of electronic states across the interface. Magnetic properties are characterized using Heisenberg exchange parameters obtained from both total-energy differences and the Liechtenstein-Katsnelson-Antropov-Gubanov formalism in the basis of maximally localized Wannier functions. Analysis of these parameters shows a strong directional anisotropy in the magnetic substrate-molecule interaction in agreement with the nature of orbital hybridization. Additionally, possible exchange mechanisms are proposed based on orbital-resolved exchange and hopping parameters. We also show that the molecular adsorption may enhance the intralayer exchange interactions, with some exchange parameters reaching up to a threefold increase in magnitude compared to the freestanding case. Finally, we observe a 100% spin polarization at the Fermi level in the cobaltocene/${\mathrm{CrI}}_3$ interface, which makes it particularly promising for spin-transport applications.

The two-dimensional (2D) Hubbard model has long attracted interest for its rich phase diagram and its relevance to high-$T_c$ superconductivity. However, reliable finite-temperature studies remain challenging due to the exponential complexity of many-body interactions. Here, we introduce an enhanced $1{\mathrm{s}}^{+}$ exponential tensor renormalization group algorithm that enables efficient finite-temperature simulations of the 2D Hubbard model. By exploring an expanded space, our approach achieves two-site update accuracy at the computational cost of a one-site update, and delivers up to 50% acceleration for Hubbard-like systems, which enables simulations down to $T\approx 0.004t$. This advance permits a direct investigation of superconducting order over a wide temperature range and facilitates a comparison with zero-temperature infinite projected entangled pair state simulations. Finally, we compile a comprehensive dataset of snapshots spanning the relevant region of the phase diagram, providing a valuable reference for artificial-intelligence-driven analyses of the Hubbard model and a comparison with cold-atom experiments.

We investigate the emergence of superconducting phases, both with zero and finite Cooper-pair center-of-mass momenta, in recently proposed unconventional $p$-wave magnets. As a result we find that while these magnetic phases are in principle compatible with a conventional pairing state at zero field, a Fulde-Ferrell phase can generally be promoted as the leading instability under the application of a finite magnetic field. Interestingly, by calculating the efficiency of the superconducting diode effect of this finite-momentum pairing state via a Ginzburg-Landau theory, we uncover that a high efficiency can be obtained in these systems for experimentally relevant spin splittings. Therefore, our prediction reveals that the experimental discovery of these materials represents a promising platform for the construction of superconducting logic circuits that may as a consequence find various technological applications.

Two-dimensional multilayer materials with an induced moiré pattern, either due to strain or relative twist between layers, provide a versatile platform for exploring strongly correlated and topological electronic phenomena. While these systems offer unprecedented tunability, their theoretical description remains challenging due to their complex atomic structures and large unit cells. A key step in constructing effective theories is determining the relevant symmetry group of these systems. Here, we use a combination of analytical methods, molecular dynamics simulations, and first-principles calculations to show that twisted atomic configurations with distinct microscopic symmetries converge to a universal moiré-scale symmetry that governs the low-energy physics. We apply this framework to three widely studied families of moiré materials—twisted bilayer graphene, twisted hexagonal boron nitride, and twisted transition metal dichalcogenides—and introduce quantitative criteria for structural and electronic equivalence grounded in numerical accuracy and experimental resolution. This emergent universality provides a robust foundation for symmetry-respecting models and offers insight into the role of commensurability in real twisted moiré systems.

We study quantum tunneling through a potential barrier whose height fluctuates in time and is modeled by Gaussian white noise. Exploiting the correspondence between Gaussian white-noise dynamics and Lindblad evolution, we recast the noise-averaged dynamics as a time-independent density-matrix scattering problem and derive fully analytical solutions. For nonrelativistic particles described by the Schrödinger equation, noise introduces dissipation, suppresses Fabry-Pérot oscillations, and produces exponentially decaying transmission. Applying the same formalism to graphene, we show that noise induces a complex longitudinal wave vector within the barrier, leading to strong suppression of transmission and Klein tunneling even at normal incidence. Within the present model, the analytical results show how the noise strength controls the attenuation of electron transmission through graphene barriers. More broadly, the formalism provides an analytical basis for investigating noisy multibarrier structures, including graphene quantum-dot confinement; assessing qubit performance, however, will require extending the treatment to explicit confinement geometries and accounting for coherence.

Long-distance spin transfer is essential for realizing scalable, all-optical magnetic logic units. In this work, we employ high-level quantum chemistry methods to demonstrate ultrafast laser-driven spin dynamics in a zigzag silicon chain functionalized with two Ni atoms. The first result of this study is the realization of coherent spin transfer in both cis and trans configurations, achieving transfer distances of 6.547 and 6.021 nm, respectively, within the subpicosecond regime, demonstrating the potential of silicon-based spin channels for ultrafast logic operations. The second outcome reveals that even minor variations in laser polarization angles can cause a significant reduction in spin-transfer fidelity. Third, we find that changes in the strength of an applied inhomogeneous magnetic field $B$ strongly affect the fidelity of spin transfer. The fourth key finding is that, for a double-pulse sequence, the fidelity of the spin-flip process is highly sensitive to the time delay between two laser pulses. Fifth, a combination of a single laser pulse and a magnetic field $B$ enables the selective addressing of individual spin centers with high spatial resolution. In particular, the cis configuration exhibits a resolution limit for Ni-Ni separation of just 3.0 Å (well below the projected CMOS scaling limit of 20 Å), highlighting its potential for miniaturization.