We study a random and quasiperiodically driven one-dimensional non-integrable PXP spin chain in a magnetic field for two distinct drive protocols. Each of these protocols involves square pulses with two driving frequencies that are integer multiples of each other. For the first class of protocols, the duration of the pulse is changed randomly by an amplitude $dT$, while for the second class we use a random/quasiperiodic dipolar drive, where the quasiperiodicity is implemented using the Thue-Morse (TM) or Fibonacci sequences. For both protocols, we identify parameter regimes for which the thermalization of the driven chain is drastically slowed down because of proximity to a two-rate drive induced exact dynamical freezing. We also study the properties of these driven system moving slightly away from the freezing limit. For the first type of protocols, we show the existence of special value of $dT$ for which the thermalization rate remains small, and provide an analytic explanation for such slow thermalization. For the second class of protocols, in contrast to random/quasiperiodic drives involving a single frequency studied earlier, we find that the TM quasiperiodic drive leads to a distinctly slower thermalization than that for drive protocols that are either periodic or follow a random or quasiperiodic Fibonacci sequence. We provide a qualitative semi-analytic understanding of these phenomena either using an exact calculation for small system sizes or carrying out a perturbative analysis in the large drive-amplitude limit. Our analysis brings out the central role of such two-frequency protocols in the reduction of heating in driven quantum systems. We discuss experiments that can test our theory.

The investigation of electronic order-quantum phase interplay in kagome lattices commonly employs the extended kagome-Hubbard model, where the critical parameters comprise on-site $\left(U\right)$ and intersite $\left(V\right)$ Coulomb interactions. In prototypical kagome metals ${\mathrm{AV}}_3{\mathrm{Sb}}_5 (\mathrm{A}=\mathrm{K}, \mathrm{Rb}, \mathrm{Cs})$, the geometrically frustrated quasi-two-dimensional architecture induces pressure-dependent complexity in vanadium $d$-electron correlations, necessitating systematic theoretical scrutiny. Utilizing the $d-dp$ model within constrained random phase approximation (cRPA), we quantified $U$, $V$, and Hund's coupling $J$ under hydrostatic pressure (0–9 GPa). While ${\mathrm{KV}}_3{\mathrm{Sb}}_5$ and ${\mathrm{RbV}}_3{\mathrm{Sb}}_5$ exhibit pressure-insensitive interaction parameters, ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ manifests anomalous discontinuities in $U$ and $V$ near 0.2 GPa, suggesting a first-order electronic phase transition. This work establishes cRPA-derived interaction landscapes as critical predictors for pressure-tunable quantum phenomena in correlated kagome systems, offering insight into the understanding of the interplay between the charge density wave transition and the double superconductivity dome in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ at low pressure.

The ${\mathrm{La}}_2{\mathrm{CoIr}}_{1-x}{\mathrm{Ti}}_x{\mathrm{O}}_6$ $(0\le x\le 1)$ double perovskite series serves as an effective platform for investigating the evolution of magnetic and electronic properties as a function of chemical pressure (doping) or hydrostatic pressure due to the interplay between the electrons' correlation $\left(U\right)$ and spin-orbit coupling (SOC). In this study, the substitution of nonmagnetic ${\mathrm{Ti}}^{4+}$ at the magnetic ${\mathrm{Ir}}^{4+}$ site leads to a systematic decrease in unit-cell volume keeping the monoclinic $P{2}_1/n$ symmetry throughout, reflecting the effect of chemical pressure along with a gradual suppression of magnetic interactions. The parent compound $(x=0)$ exhibits a ferromagneticlike state with a Curie temperature $T_{\mathrm{C}}=92$ K, which continuously evolves into an antiferromagnetic ground state upon full Ti substitution $(x=1)$ with a Néel temperature $T_{\mathrm{N}}=14.6$ K. Isothermal magnetization measurements reveal a hysteresis behavior with steplike feature at zero field, indicative of a noncollinear magnetic ordering. Additionally, the enhancement of magnetization under hydrostatic pressure on ${\mathrm{La}}_2{\mathrm{CoIrO}}_6$ $(x=0)$ suggests the presence of piezomagnetic behavior. Thermal expansion measurements on ${\mathrm{La}}_2{\mathrm{CoIrO}}_6$ highlight a coupling between spin and lattice degrees of freedom. The pressure dependence of the transition temperature in the zero-pressure limit, calculated using Ehrenfest's relation, shows good agreement with magnetization data under applied pressure. First-principles density functional theory calculations performed for $x=\mathrm{0}, 0.5$, and 1 further reveal that strong SOC associated with Ir plays a decisive role in shaping the electronic band structure, with the insulating gap progressively widening as Ti content increases from 0.28 eV $(x=\mathrm{0})$, 0.44 eV $(x=0.5)$, and 1.01 eV $(x=1)$. The magnetic moment decreased more than 50% for $x=0.5$, showing the decrease in magnetic exchange pathways. Collectively, these results establish ${\mathrm{La}}_2{\mathrm{CoIr}}_{1-x}{\mathrm{Ti}}_x{\mathrm{O}}_6$ as a model system for exploring the interplay among electrons' correlation, SOC, chemical pressure, and doping-driven magnetic phase transitions, providing valuable insights into the tunability of electronic and magnetic properties in complex oxides.

We report on the molecular beam epitaxy (MBE) growth and characterization of samarium nitride (SmN) thin films on MgO(001), focusing on the tunability of their electronic and magnetic properties via growth temperature and nitrogen flux. Despite the large lattice mismatch, all films exhibit high structural quality, confirmed by reflection high-energy electron diffraction and x-ray diffraction, with minimal strain and no secondary phases. By systematically varying the nitrogen-to-samarium ratio and substrate temperature, we demonstrate a transition from insulating to metallic behavior with carrier concentrations spanning an order of magnitude. All samples exhibit robust ferromagnetism with Curie temperatures between 27–30 K, although no superconductivity is observed down to 0.35 K, even in the most conductive samples. These findings suggest that superconductivity in SmN may be highly sensitive to carrier concentration, disorder, and interface effects. Our results provide a pathway for high-quality synthesis of SmN thin films and its potential monolithic integration of spintronic devices based on rare-earth nitride systems.

We present a systematic, quasiautomated methodology for generating electronic models in the framework of second-principles density functional theory (SPDFT). This approach enables the construction of accurate and computationally efficient models by deriving all necessary parameters from first-principles calculations on a carefully designed training set. A key feature of our method is the enforcement of space-group symmetries, which reduces both the number of independent parameters and the required computational effort. The formalism includes improved treatments of one-electron Hamiltonians, electron-lattice coupling, through both linear and quadratic terms, and electron-electron interactions, enabling accurate modeling of structural and electronic responses. We apply the methodology to ${\mathrm{SrTiO}}_3$, LiF, and metallic Li materials that present a wide variety of properties as corresponds to a transition-metal perovskite, a wide-band-gap ionic insulator, and a free-electron metal, respectively. In all cases, the resulting models reproduce DFT reference data with high fidelity across various atomic configurations and charge states. Our results validate the robustness of the approach and highlight its potential for simulating complex phenomena such as polarons and excitons. This work lays the foundation for extending SPDFT to real-time simulations of optoelectronic properties and further integration with machine-learning methods.

The layer-engineering-dependent electronic and optical properties of two-dimensional 1T-$\mathrm{HfSe}{}_2$/1T-$\mathrm{SnSe}{}_2$ van der Waals (vdW) heterostructure are investigated by employing first-principle density functional theory. In the independent particle approximation framework, the twist-free heterobilayer exhibits indirect-band-gap features similar to constituent monolayers, however at particular rotational angles $\theta ={16.10}^{\circ }$ and ${43.90}^{\circ }$, the twisted heterobilayers demonstrate direct-band-gap features. The direct band gap in twisted unit cells arises from atomic registry and corrugation effects, beyond simple zone folding. Furthermore, the emergence of a direct band gap supports allowed optical transitions, consistent with optical selection rules, reinforcing the link between band-gap character and optical activity. Semiconducting states to metallic phase transitions emerge under the applications of electric fields. The heterobilayer shows strong optical response in the visible range, while twisting induces both red- and blueshift features, with additional infrared peaks emerging under fields of $E_{\mathrm{field}}=0.4\text{V}/\text{Å}$ and $E_{\mathrm{field}}=0.5\text{V}/\text{Å}$. Bethe–Salpeter equation calculations reveal previously unreported multiple bright excitons in the twist-free heterostructure. We find contribution of both interlayer and interband electronic transitions for the observed strongest excitonic peak. These findings highlight the tunable light–matter interactions in layered two-dimensional materials, opening avenues for engineering direction-dependent optical functionalities in next-generation optoelectronic devices.

Phase transitions in solids are often accompanied by structural changes, but subtle lattice distortions can remain hidden from conventional crystallographic probes, hindering the identification of the correct order parameters. A case in point is ${\mathrm{Ca}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$, a correlated polar ruthenate with well-characterized phase transitions, whose ground-state structure has recently become a subject of debate. This uncertainty stems from extremely small atomic displacements $(\sim 0.001\AA )$ between competing phases, beyond the resolution of x-ray diffraction, neutron scattering, or optical second-harmonic generation. In this work, we propose a method to detect hidden symmetry breaking by leveraging nonlinear transport induced by quantum geometry. We show that ${\mathrm{Ca}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$ is a Weyl chain semimetal in both phases. The low-symmetry phase, classified as an altermagnet by symmetry, features distorted topological surface states that are asymmetric along the polar $\left(b\right)$ axis. However, the nonrelativistic spin splitting is too weak $(\sim 0.1\mathrm{meV})$ to be resolved directly, regarding the altermagnetism. In contrast, Weyl chains generate a large quantum metric at the Fermi surface, leading to nonlinear conductivities that are orders of magnitude stronger in the low-symmetry phase. A longitudinal nonlinear conductivity along the polar axis emerges exclusively in this phase, providing a sensitive probe to qualitatively distinguish it from the high-symmetry structure and demonstrate the emergence of altermagnetism, which is confirmed by a recent experiment. Our work establishes a route for identifying hidden symmetry breaking in complex quantum materials through the interplay of crystal symmetry, topology, and nonlinear quantum transport.

We present the results of a mean-field analysis of the temperature evolution of a ferromagnetic Stoner transition in a two-dimensional (2D) system with an isotropic dispersion ${\varepsilon }_k\propto k^{2\alpha }$, which for $\alpha >1$ models flat dispersions in various multilayer graphene systems in a displacement field. This study is an extension to a finite $T$ of previous studies at $T=0$, which found both first-order and second-order Stoner transitions, depending on the value of $\alpha$ and special behavior at $\alpha =1$ and $\alpha =2$. We find that the Stoner transition at a finite $T$ displays new features not seen at $T=0$. The most interesting one is the reentrant behavior, where the ordered state emerges as temperature is increased. This behavior develops at $\alpha >1.4$ and the range where it holds increases with $\alpha$. We conjecture that the reentrant behavior is the fundamental feature of the Stoner transition in 2D, not sensitive to the details of the electronic structure.

The motion of dopants in magnetic spin lattices has received tremendous attention for at least four decades due to its connection to high-temperature superconductivity. Despite these efforts, we lack a complete understanding of their behavior, especially out of the equilibrium and at nonzero temperatures. In this paper, we take a significant step towards a much deeper understanding based on state-of-the-art matrix-product-state calculations. In particular, we investigate the nonequilibrium dynamics of a dopant in two-leg $t\text{−}J$ ladders with antiferromagnetic XXZ spin interactions. In the Ising limit, we find that the dopant is localized for all investigated nonzero temperatures due to an emergent disordered potential, with a localization length controlled by the underlying correlation length of the spin lattice, which increases exponentially with decreasing temperature. The dopant, hereby, only delocalizes asymptotically in the zero temperature limit. This greatly generalizes the localization effect discovered recently in Hilbert space fragmented models [Phys. Rev. Res. 6, 023325 (2024), SciPost Phys. Core 7, 054 (2024)]. In the presence of spin-exchange processes at rate $\alpha$, the dopant diffuses with a diffusion coefficient, $D_h$, depending nonmonotonically on $\alpha$. It initially increases linearly as $D_h\propto \alpha$ for $\alpha \ll 1$ before dropping off as ${\alpha }^{-1}$ for $\alpha >1$. Moreover, we show that the underlying spin dynamics at infinite temperature behaves qualitatively the same, albeit with important quantitative differences. We substantiate these findings by showing that the dynamics features self-similar scaling behavior, which strongly deviates from the Gaussian behavior of regular diffusion, especially for weak spin exchange. Finally, we show that the diffusion coefficient $D_h$ follows an Arrhenius relation at high temperatures, whereby it is exponentially suppressed upon cooling.

Berry curvature can drastically modify the electron dynamics, thereby offering an effective pathway for electron manipulation and novel device applications. Compared to zero-dimensional nodal points in Weyl/Dirac semimetals, higher-dimensional extended nodal structures, such as nodal lines and nodal surfaces, are more likely to intersect the Fermi surface, leading to large Berry curvature effects without fine-tuning the chemical potential. In this work, we propose a strategy that utilizes straight nodal lines (SNLs) and flat nodal surfaces (FNSs) to design large Berry curvature effects, and we exhaustively tabulate SNLs and FNSs within the 1651 magnetic space groups (MSGs). We demonstrate that SNLs and FNSs can generate large Berry curvature widely distributed in the Brillouin zone. As an application, we identify 158 MSGs that host FNSs, SNLs, or both and allow for nonvanishing anomalous Hall conductivity (AHC). Based on these 158 MSGs, we screen materials from the MAGNDATA magnetic material database for high-throughput calculations, identifying 60 materials with AHC values exceeding $500{\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$. We select the candidate materials ${\mathrm{SrRuO}}_3$ and ${\mathrm{Ca}}_2{\mathrm{NiOsO}}_6$ to demonstrate the contributions of FNSs and SNLs to one and two nonvanishing AHC components, respectively. We also investigate the tuning of AHC through symmetry breaking, outlining all possible symmetry-breaking pathways, and select the candidate material HoNi to demonstrate this approach by applying an external magnetic field. Additionally, we identify Berry curvature quadrupoles in the candidate materials, indicating that our strategy can be generalized to Berry curvature multipole effects. Our work will guide both the theoretical and experimental design of materials with large Berry curvature effects, with significant implications for a wide range of device applications.

Balancing efficiency enhancement and cost reduction is crucial for advancing solar energy and photovoltaic devices. One of the primary sources of energy loss, leading to reduced efficiency, is nonradiative electron-hole recombination within these devices. In this study, we comprehensively investigated the nonradiative properties of excited-state carriers in quaternary Kesterite (KS) and Stannite (ST) phase $\mathrm{I}\text{−}{\mathrm{II}}_2\text{−}\mathrm{III}\text{−}{\mathrm{VI}}_4$ chalcogenide compounds using first-principles calculations combined with nonadiabatic molecular dynamics (NAMD). We identified the characteristics of chemical bond elongation, electron localization and bandgap fluctuations induced by cation modulation. Specifically, forming quaternary structures by introducing Zn and substituting $\mathrm{I}{\mathrm{n}}^{3+}$ with $\mathrm{G}{\mathrm{a}}^{3+}$ and $\mathrm{C}{\mathrm{u}}^{+}$ with $\mathrm{A}{\mathrm{g}}^{+}$ resulted in increased bandgaps. Through a detailed analysis of orbital and vibrational components, we elucidated the principles for regulating nonadiabatic coupling and carrier lifetimes, including strategies to suppress the $t_2$ orbital of I-site cations, low-frequency optical phonons and anti-Zeno effects. Compared with the KS structure, the ST structure retains higher symmetry, with suppressed low-frequency electron-vibration interactions, leading to reduced nonradiative recombination. These findings provide insights into effectively reducing nonradiative recombination processes, thereby highlighting the potential of $\mathrm{I}\text{−}{\mathrm{II}}_2\text{−}\mathrm{III}\text{−}{\mathrm{VI}}_4$ chalcogenide compounds for high-efficiency photovoltaic applications.

Building a fault-tolerant quantum computer requires physical qubits with exceptionally low error rates. Majorana-based tetron qubits are predicted to exhibit error rates that decrease exponentially with inverse temperature and length of each topological superconducting wire in the tetron. In contrast to this prediction, we show that small temporal variations of the chemical potential can cause errors that grow linearly with tetron length at zero temperature. These errors stem from leakage into excited quasiparticle states, which ultimately poison Majorana modes at opposite ends of the tetron, causing errors. We further demonstrate that the dynamics of this leakage is captured by the half Landau-Zener effect, which dictates its dependence on key system parameters such as the superconducting gap, chemical potential variations, and dynamic changes in the spatial profile of Majorana modes. These results motivate further investigations into the impact of leakage on qubit performance and potential mitigation strategies.

The laser-assisted field evaporation of oxides by deep UV (257.5 nm wavelength, 4.8 eV photon energy) and UV (355 nm, 3.5 eV) laser light was investigated by measuring the detection rate as a function of laser pulse energy. The experimental approach, where the voltage and hence the electrostatic field are held constant, was performed on the metallic alloy Ni-20Cr as well as chromia and ${\mathrm{SrTiO}}_3$. The detection rate was recorded as a function of laser pulse energy as well as field estimates. The experiments confirm evaporation being facilitated by a thermal pulse via the laser for the metallic alloy, thereby validating the strategy. For oxides, the relation did not follow an Arrhenius law expected for a temperature pulse. Instead, the measurements closely followed an expression of the form $A{x}_1+B{x_2}^{2}exp\left\{-\frac{C}{x_2}\right\}$, where $x_1=E_{\mathrm{Laser}}$ and $x_2=\left(T_0+k{E}_{\mathrm{Laser}}\right)$ with $A$, $B$, $C$, and $k$ being constants, $T_0$ the base temperature, and $E_{\mathrm{Laser}}$ the laser pulse energy. Hence, we propose that the evaporation mechanism involves a reduction of the energy barrier through accumulation of charge carrier holes at the apex. Hole generation occurs via photoionization and photoinduced tunneling of electrons. Investigations with a variation of the electrostatic field during evaporation of chromia underline the proposed mechanisms. Previously unexplained laser-assisted field evaporation of MgO, ${\mathrm{Fe}}_3{\mathrm{O}}_4$, and GaN in atom probe experiments with UV laser light fits with the new observations. Further theoretical and experimental research is needed to confirm or refute the proposed mechanism.

Magnetic anisotropy is a key feature of rare earth materials from permanent magnets to heavy fermions. We explore the complex interplay of Kondo physics and anisotropy, and their effect on different experimental probes of magnetic anisotropy in a minimal $J=3/2$ Anderson impurity model using the numerical renormalization group. While anisotropy suppresses Kondo screening, virtual valence fluctuations enhance the anisotropy. We find distinct renormalization of the magnetic anisotropy measured via dynamical spin response (inelastic neutron scattering) versus electronic excitations in the impurity spectral function (resonant inelastic x-ray and scanning tunneling spectroscopy). The two measurement types have different responses and dependencies on the temperature and Kondo scales.

Ru-$\mathrm{Ce}{\mathrm{O}}_2$ catalysts, which combine the high catalytic activity of ruthenium with the unique redox properties of ceria, have demonstrated significant potential in various catalytic reactions including $\mathrm{C}{\mathrm{O}}_2$ methanation, ammonia synthesis, and oxidation-reduction processes. However, the physical mechanisms underlying their high performance remain incompletely understood primarily because there is limited knowledge regarding the structural evolution of Ru-$\mathrm{Ce}{\mathrm{O}}_2$ catalysts under near-realistic conditions. In this work we propose a strategy to investigate this structural evolution by integrating a global search algorithm based on first-principles computational data with electronic structure calculations to study the behavior of Ru-$\mathrm{Ce}{\mathrm{O}}_2$ under different redox conditions. Our results reveal that oxidizing conditions promote the dispersion of Ru clusters into atomic forms. These dispersed clusters are stabilized by the formation of bonds between Ru and lattice oxygen on the $\mathrm{Ce}{\mathrm{O}}_2$ surface. In contrast, reducing conditions enhance oxygen vacancy formation, which leads to the aggregation and sintering of atomic Ru species into larger metallic structures. Furthermore, charge transfer between Ru clusters and $\mathrm{Ce}{\mathrm{O}}_2$ plays a critical role. Oxidizing conditions facilitate electron transfer from Ru to $\mathrm{Ce}{\mathrm{O}}_2$, thereby stabilizing dispersed configurations while reducing conditions diminishing this interaction and promoting aggregation. These findings underscore the tunability of Ru cluster morphology through redox control and provide valuable insights into optimizing Ru-$\mathrm{Ce}{\mathrm{O}}_2$ catalysts for enhanced performance.

The numerical simulation of two-dimensional quantum many-body systems away from equilibrium constitutes a major challenge for all known computational methods. We investigate the utility of tree tensor network (TTN) states to solve the dynamics of the quantum Ising model in two dimensions. Within the perturbative regime of small transverse fields, TTNs faithfully reproduce analytically known, but nontrivial and physically interesting dynamics of magnetic domains, for lattices up to $16\times 16$ sites. Limitations of the method related to the rapid growth of entanglement entropy are explored within more general, paradigmatic quench settings. We provide and discuss comprehensive benchmarks regarding the benefit of GPU acceleration and the impact of using local operator sums on the performance.