Owing to the broken inversion symmetry at the surface, thin Bi films are expected to exhibit interesting electronic and topological properties stemming from its large spin-orbit coupling. Furthermore, the properties of Bi thin films are also governed by the coupling to the underlying substrate. In this work, we scrutinize the formation and properties of the $(\sqrt{3}\times \sqrt{3})\text{R}{30}^{\circ }$ Bi wetting layer on Ge(111) using scanning tunneling microscopy and first-principles simulations. The deposition of Bi on Ge(111) leads to the de-reconstruction of the $\mathrm{c}(2\times 8)$ adatom structure of Ge(111) and the formation of Ge islands. The unreconstructed Ge terraces and islands are covered by a semiconducting $(\sqrt{3}\times \sqrt{3})\text{R}{30}^{\circ }$ Bi wetting layer. The elementary building block of the Bi wetting layer is a Bi trimer, which is located on a ${\mathrm{T}}_4$ site of the underlying Ge(111) substrate. This Bi trimer has a well-defined electronic state at $-0.4\mathrm{e}\mathrm{V}$. The edges of the small Bi covered Ge islands, which are slightly metallic, are mainly of the armchair edge configuration. The most abundant defects in the Bi wetting layer are antiphase boundaries and single Bi trimer vacancies. Our work lays the foundation to investigate the topological nature of the Bi trimer wetting layer and any layers grown on top.

Control and manipulation of quantum states by measurements and bath engineering in open quantum systems, like in a quantum computer, have emerged as new paradigms in many-body physics. Taking a prototypical example of Josephson junction arrays (JJAs), we show how monitoring through continuous weak measurements and feedback can transform an insulating steady state in JJAs to a superconductor (SC) and vice versa. We show that the quantum feedback, when not too large, is crucial to realize such a superconducting steady state by maintaining an effective temperature in a semiclassical limit. However, we show that large feedback can destroy superconductivity by enhancing quantum phase fluctuations. Thus, dissipation and phase fluctuations in the presence of monitoring have fundamental differences from those in the well-studied case of JJAs in contact with an equilibrium Ohmic bath. In general, a description in terms of only an effective temperature is not adequate for the monitored JJAs. Using a variational approximation, and by considering various limiting cases, we demonstrate that these differences can give rise to reentrant SC-insulator phase transitions leading to an unusual inverse transition from a seemingly low-effective-temperature insulating normal state to a superconducting state at intermediate temperature.

For the first time, an approach coupling the variable charge model based on a tight-binding approach within the second moment approximation (SMTB-QB) and the Effective Site Energy (ESE) is used to obtain the phase diagram of a mixed oxide. SMTB-QB allows one to calculate the site energies of all atoms in random solid solution for the ${\mathrm{SnTiO}}_2$ mixed oxide. These energies are analyzed within the ESE model as a function both of the local environment (number of Sn nearest neighbors) and of the nominal concentration. The almost symmetrical miscibility gap is well reproduced by Monte Carlo simulations. The ESE model shows that the apparent symmetry of the phase diagram actually comes from two highly asymmetrical thermodynamic forces. The local effect that induces a homoatomic short range order (SRO) dominates when Sn is the minority element, while the nonlocal effect that does not induce SRO dominates when Sn is the majority element. This result demonstrates that the ESE model's ability to analyze the driving forces that govern phase diagrams, which has been widely demonstrated for bimetallic alloys, also extends to mixed oxides.

β relaxation is a key dynamic feature of glasses, influencing a wide range of properties. Although many factors, such as thermal history and composition, have been extensively studied and reported to significantly influence β relaxation, considerable controversy persists, limiting a deeper understanding of β relaxation in glasses. Here, we employ a binary metallic glass (MG), ${\mathrm{Ce}}_{75}{\mathrm{Al}}_{25}$, as a model system with a polymorphic crystallization process to minimize thermally induced compositional deviations. This enables us to separate and analyze the thermal and compositional impacts on β relaxation using dynamic mechanical analysis (DMA) across various thermal annealing treatments below the glass transition temperature $\left(T_g\right)$ and above the crystallization temperature $\left(T_x\right)$. We clarify that relaxation dynamics at temperatures not far below $T_g$ are primarily governed by α relaxation, and changes to the energy states of glasses (or atomic structures) through sub-$T_g$ annealing have minimal impact on β relaxation signals. These findings suggest that the β relaxation of ${\mathrm{Ce}}_{75}{\mathrm{Al}}_{25}$ MG is in fact a pseudo Johari-Goldstein (JG) relaxation rather than a genuine JG β relaxation. It is suggested that β relaxation behaves more like a localized dynamic event involving only a fraction of atoms, which may aid in crystallization nucleation below $T_g$. By contrasting the effects of thermal annealing on other Ce-Al binary MGs with primary crystallization processes, we further reveal that the position of β relaxation is primarily composition-dependent. These results shed new light on the thermal and compositional effects on β relaxation in MGs.

Describing nonequilibrium quantum dynamics remains a significant computational challenge due to the growth of spatial entanglement. The tensor network influence functional (TN-IF) approach mitigates this problem for computing the time evolution of local observables by encoding the subsystem's influence functional path integral as a matrix product state, thereby shifting the resource governing computational cost from spatial entanglement to temporal entanglement. We extend the applicability of the TN-IF method to two-dimensional lattices by demonstrating its construction on tree lattices and proposing a belief propagation (BP) algorithm for the TN-IF, termed influence functional BP (IF-BP), to simulate local observable dynamics on arbitrary graphs. Even though the BP algorithm introduces uncontrolled approximation errors on arbitrary graphs, it provides an accurate description for locally treelike lattices. Numerical simulations of the kicked Ising model on a heavy-hex lattice, motivated by a recent quantum experiment, highlight the effectiveness of the IF-BP method, which demonstrates superior performance in capturing long-time dynamics where traditional tensor network state-based methods struggle. Our results further reveal that the temporal entanglement entropy only grows logarithmically with time for this model, resulting in a polynomial computational cost for the whole method. We further construct a cluster expansion of IF-BP to introduce loop correlations beyond the BP approximation, providing a systematic correction to the IF-BP estimate. We demonstrate the power of the cluster expansion of the IF-BP in simulating the quantum quench dynamics of the two-dimensional transverse field Ising model, obtaining numerical results that improve on the state-of-the-art.

Using density functional theory calculations and atomistic spin simulations, we propose the existence of room-temperature chiral magnetic textures in ${\mathrm{Fe}}_{2}X\left(X=\mathrm{S},\mathrm{Se},\mathrm{Te}\right)$ monolayers. The intrinsic broken inversion symmetry and strong spin-orbit coupling give rise to an interfacial Dzyaloshinskii-Moriya interaction, which, in conjunction with out-of-plane magnetic anisotropy, enables the stabilization of topological magnetic textures, such as skyrmions and spin spirals, in the absence of an external magnetic field. The chiral spin textures exhibit remarkable thermal stability at room-temperature, significantly enhancing their potential for application in next-generation spintronic devices.

Magnetic excitations of the exchange-dipole quasi-one-dimensional XXZ antiferromagnet are studied in the ordered phase. We observe a transformation of the electron spin resonance (ESR) spectrum when crossing the Néel temperature near 0.2 K. The single-mode ESR of a correlated XXZ chain transforms in the multimode spectrum in the ordered phase. The multimode spectrum consists mainly of the intensive mode of a single correlated chain, which is surrounded and/or indented by numerous weak satellites. The number of securely fixed modes is eight at $\mathbf{H}\parallel b$ and twelve at $\mathbf{H}\parallel a$. In addition to the multimode resonance observed at the transverse polarization of the microwave and static magnetic fields, we reveal a wide band of absorption by ($k$,–$k$) pairs of quasiparticles at the longitudinal polarization. This kind of absorption of microwaves occurs both in the ordered and specific spin-liquid phases, revealing the presence of quasiparticles in the specific spin-liquid phase.

Ferroelectric superlattices (SLs) are emerging as a cutting-edge solution to various challenges, such as lowering the coercive field, increasing polarization and dielectric constant, mitigating wake-up, and enhancing endurance. However, a comprehensive atomic-scale understanding and predictive design framework for these SLs still requires further investigation. Herein, based on group theory and first-principles simulations, we explored stacking direction dependent properties of ${\mathrm{HfO}}_2/{\mathrm{ZrO}}_2$ (HZO) SLs and established a strong relationship between Raman-mode frequencies and the SL stacking direction, which further highlights that Raman modes can be used as effective descriptors for uncovering the local ordering in such SLs. Additionally, we discovered that a cell-doubling distortion mode intrinsic to the $\left[010\right]$ HZO SL leads to the emergence of an intermediate orthorhombic $Pmn{2}_1$-like phase during the transitions between the antiferroelectric $P{4}_2/nmc$ tetragonal and ferroelectric $Pca{2}_1$ orthorhombic phases. This intermediate phase remarkably reduces the energy barrier between the two states, playing a pivotal role in achieving nearly wake-up-free ferroelectricity. Moreover, the reduction in this barrier decreases the energy required for ferroelectric polarization switching, lowering the coercive field while retaining the polarization magnitude of bulk ${\mathrm{HfO}}_2$. Our findings provide an opportunity for the development of next-generation low-voltage memory devices.

Gallium oxide ($\mathrm{G}{\mathrm{a}}_2{\mathrm{O}}_3$) has emerged as a promising ultra-wide bandgap semiconductor for next-generation power electronics and optoelectronic devices. However, the thermal transport properties of $\mathrm{G}{\mathrm{a}}_2{\mathrm{O}}_3$, particularly in its amorphous state, remain poorly understood, even though they are critically important for device reliability. In this work, we employed molecular dynamics simulations with a machine-learned neuroevolution potential (NEP) to investigate the structure-thermal property relationship between structure and thermal properties in $a\text{−}\mathrm{G}{\mathrm{a}}_2{\mathrm{O}}_3$ across a comprehensive density range ($3.5–8.0\mathrm{g}/\mathrm{c}{\mathrm{m}}^3$). Through systematic analysis of radial distribution functions, angular distributions, and coordination environments, we identify two distinct structural transitions at $5.25\mathrm{g}/\mathrm{c}{\mathrm{m}}^3$ and $6.50\mathrm{g}/\mathrm{c}{\mathrm{m}}^3$, corresponding to the progressive transformation of Ga coordination from fourfold to sixfold coordination and O coordination from threefold to fourfold. Homogeneous nonequilibrium MD simulations coupled with spectral heat current analysis reveal that these structural changes induce sharp enhancements in thermal conductivity, mediated through simultaneous improvements in both propagons and diffusons. The increase in atomic coordination creates more direct atomic pathways while strengthening interatomic coupling, ultimately enabling a sixfold increase in thermal conductivity across the studied density range. Our findings establish fundamental structure-property relationships in $a\text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ and suggest general design principles for thermal management in amorphous semiconductors undergoing coordination polyhedral transitions.

We construct an electrical all-bands-flat (ABF) lattice and experimentally generate compact localized states (CLSs) therein. The lattice is a diamond (rhombic) chain and implemented as a network of capacitors and inductors, as well as voltage inverters (using operational amplifiers) in order to introduce a $\pi$ flux within each diamond. The network's normal modes split into three flat bands, and the corresponding CLSs can be excited in isolation via a two-node driving at the flat-band frequencies. We also examine the role of the lattice edges and their interaction with the CLSs. Finally, we compare the experimental results to tight-binding predictions and obtain very good agreement. This analysis paves the way for further experimental implementations of ABF systems in electric networks, especially with an eye towards exploring their interplay with nonlinearity.

The kagome lattice has attracted extensive attention due to the diverse magnetic properties and nontrivial electronic states generated by its unique atomic arrangement, which provides an excellent system for exploring macroscopic quantum behavior. Here, we report the anomalous transport properties in 166-type kagome metal ${\mathrm{ZrV}}_6{\mathrm{Sn}}_6$ single crystals. The quadratic and linear magnetoresistance (LMR) can be observed depending on the directions of the field and the current. Integrating Hall resistivity and quantum oscillation measurements, we found that the LMR could match well with the Abrikosov model. However, this model encounters difficulties in explaining the anisotropy of the magnetoresistance. To solve the issue, we extrapolate the Abrikosov model to the case of two-dimensional linear dispersion. It was found that, when the field is parallel to the linear dependence momentum, the quantized energy is ${\epsilon }_n^{\pm }$ = $\pm v\sqrt{p^2+2eHn/c}$, resulting in LMR. By contrast, when it is parallel to the nonlinear dependence momentum, the energy is ${\epsilon }_n^{\pm }$ = $\pm v\sqrt{2eHn/c}$, without yielding LMR. Through the combination of experiment and theory, the modified Abrikosov model could interpret the macroscopic quantum transport in ${\mathrm{ZrV}}_6{\mathrm{Sn}}_6$ crystal. The present research provides a new perspective for understanding the LMR behavior.

Bounded by crossover lines exhibiting universal scaling, the supercritical regime above the critical end point is characterized by strong fluctuations and intriguing phenomena. In this study, we extend this notable concept of supercritical crossover to the quantum critical end point (QCEP), by studying the prototypical mixed-field quantum Ising and Potts models through tensor network calculations and scaling analyses. We reveal the existence of quantum supercritical (QSC) crossover lines, determined by not only response functions but also quantum information quantities, near the QCEP. A supercritical scaling law, $h\sim {(g-g_c)}^{\mathrm{\Delta }}$, is found, where $g$ ($h$) is the transverse (longitudinal) field, $g_c$ is the critical field, and $\mathrm{\Delta }$ is the so-called gap exponent of the QCEP. Moreover, we demonstrate that the QSC crossover line acts as a boundary for the emergence of dynamical singularities in quench dynamics. This singularity manifests as a distinctive cusp with a critical exponent of 1/2, signaling a new dynamical universality class. We also propose utilizing Rydberg atom arrays as an experimental platform to observe these QSC crossovers and dynamical singularities. Our work establishes a theoretical framework for understanding the role of a QCEP and associated supercritical crossovers in both equilibrium and nonequilibrium quantum many-body systems.

The geometry of quantum states can be an indicator of criticality, yet it remains less explored under non-Hermitian topological conditions. In this work, we unveil diverse scalings of the quantum geometry over the ground-state manifold close to different topological phase transitions in a non-Hermitian long-range extension of the Kitaev chain. The derivative of the geometric phase, as well as its scaling behavior, shows that systems with different long-range couplings can belong to a distinct critical class. Near certain criticalities, we further find that the Wannier state correlation function associated with the extended Berry connection of the ground state exhibits spatially anomalous behaviors. Finally, we analyze the scaling of the quantum geometric tensor near phase transitions across exceptional points, shedding light on the emergence of a distinct critical class.

Infinite-layer nickelate superconductors are typically synthesized as thin films and thus include, besides the more bulk-like inner layers, distinct surface and interface layers in contact with the vacuum and substrate, respectively. Here, we employ density-functional theory and dynamical mean-field theory to investigate how electronic correlations influence these surface and interface regions. Our results show that electronic correlations can significantly modify the electronic structure, even driving surface layers into a Mott-insulating state with a $3d^8$ electronic configuration. Moreover, surface termination effects induce a polar field that can shift the $\mathrm{\Gamma }$ and $A$ pocket above the Fermi level, even for the undoped parent compound ${\mathrm{NdNiO}}_2$. Finally, for an $n$-type interface, often synthesized experimentally, we find the Ti $3d$ orbitals to become electron doped.

High pressure, exemplifying extreme environments, offers opportunities to extensively probe the thermophysical properties and thermochemical reactions of materials, enabling numerous practical applications. Recent studies highlight nonencapsulated ultrathin semiconducting bismuth oxyselenide ($\mathrm{B}{\mathrm{i}}_2{\mathrm{O}}_2\mathrm{Se}$) as an exceptional candidate for exploring thermal transport properties under elevated pressure, with potential implication for advanced high-speed and lower-power electronic devices. Here we employ in situ thermal measurements alongside first-principles calculations to uncover a unique switch of thermal conductivity (${\kappa }_{\mathrm{L}}$) anisotropy in $\mathrm{B}{\mathrm{i}}_2{\mathrm{O}}_2\mathrm{Se}$, occurring independent of any phase transition phenomenon under pressure. This unique phenomenon, previously unobserved experimentally and unreported theoretically for other known materials, arises from the interplay between higher-order four-phonon processes and interatomic interactions, which are modulated by pressure. These competitive mechanisms alter phonon propagation, leading to a reversal in the anisotropy of ${\kappa }_{\mathrm{L}}$. Especially, along the cross-plane direction, the pressure-dependent contributions of high-order phonon anharmonicity initially increase but subsequently decrease. Using Raman spectroscopy, a diamond anvil cell, and time-domain thermoreflectance, we systematically probe the intrinsic phonon line shape of phonon branches, as well as ${\kappa }_{\mathrm{L}}$ up to 24 GPa. Our findings reveal the higher-order phonon anharmonicity contribution up to a $\sim 63\%$ to heat transfer in cross-plane direction, while the in-plane direction effectively bypasses the heating-carrying phonons. This study delivers fundamental insights into understanding novel heat conduction phenomena for the advancement of flexible thermal-energy-related applications under extreme conditions, including pressure sensors designed for wearable technology utilized in deep-sea exploration, oil drilling, and space missions.

The quantum conductance of one-dimensional (1D) circuits built on flat (Euclidean) two-dimensional electron gases (2DEGs) is known to display a symmetric response to the inversion of Rashba spin-orbit coupling fields in Aharonov-Casher (AC) interference patterns. Here, we show that this symmetry breaks down in curved (non-Euclidean) 1D circuits defined on spherical 2DEGs. We demonstrate that this is a consequence of parallel transport and holonomy of the electronic spin on the surface of the sphere, and that a symmetric response can be recovered when considering the parallel transport condition as an offset shifting the AC pattern. We discuss 1D triangular circuits defined along geodesic arcs on the sphere as a case study, and generalize it to regular polygons and parallel curves of given latitude.

As a member of the rocksalt lead chalcogenides, PbS with chemical stability and Earth-abundant sulfur holds great promise to exhibit comparable thermoelectric performance as its sister compounds PbTe and PbSe. Owning to their similar thermal transport behavior, increasing the electrical properties of PbS becomes a goal in the thermoelectrical study. By choosing Ga-doped PbS, we perform high-pressure measurements of the structural and electrical properties. The significant enhancement of the thermoelectric power factor of 61 $\mu \mathrm{W}$ ${\mathrm{cm}}^{-1}{\mathrm{K}}^{-2}$ at room temperature is obtained at pressure of around 2.2 GPa. This notable improvement is found to stem from the dramatic increase in the Seebeck coefficient, without sacrificing the electrical conductivity. Such an enhancement is proposed to be related to the topological phase transition from a trivial state (narrow band gap semiconductor) to a topologically nontrivial state (topological crystalline insulator). This discovery underscores the potential benefits of approaching the topological state for further enhancing thermoelectric performance.

Two-dimensional silicon carbide (2D-SiC) is a promising host material for quantum bits (qubits) due to its stable structure, wide band gap, and the naturally abundant zero-nuclear-spin isotopes. In this work, first-principles calculations were conducted to investigate defect centers in 2D-SiC resulting from the doping of B, N, O, P, and S nonmetal atoms. Among the 20 defect centers examined, the neutral ${\mathrm{O}}_{\mathrm{C}}{\mathrm{V}}_{\mathrm{Si}}$ and ${\mathrm{S}}_{\mathrm{C}}{\mathrm{V}}_{\mathrm{Si}}$ are identified as particularly promising candidates, displaying spin-triplet ground states, high Debye-Waller (DW) factors of 44.93% and 34.75%, and short radiative lifetimes of 28.546 ns and 109.230 ns, respectively. An analysis of defect formation energies confirms their thermodynamic stabilities. Furthermore, the simulated photoluminescence spectra and hyperfine tensors provide a theoretical foundation for the experimental identification of ${\mathrm{O}}_{\mathrm{C}}{\mathrm{V}}_{\mathrm{Si}}$ and ${\mathrm{S}}_{\mathrm{C}}{\mathrm{V}}_{\mathrm{Si}}$ defects in 2D-SiC.

We present a continuous nonlocal model that faithfully replicates the rich topological and spectral features of the Su-Schrieffer-Heeger (SSH) model. Remarkably, our model shares the SSH models' bulk energy spectrum, eigenstates, and Zak phase—hallmarks of its topological character—while introducing a tunable length-scale $a$ quantifying nonlocality. This parameter allows for a controlled interpolation between nonlocal and local regimes. Furthermore, for a specific value of $a$ the exact spectral equivalence to the discrete SSH model is established. Distinct from previous continuous analogs based on Schrödinger or Dirac-type Hamiltonians, our approach maintains chiral symmetry, does not require an external potential, and features periodic energy bands. On finite domains, the model supports a flat band with zero energy formed by a countable infinite set of exponentially localized zero-energy edge states of topological origin. Beyond SSH, our method lays the foundation for constructing nonlocal, continuous analogs of a wide class of bipartite and multipartite lattices, opening paths for theoretical exploration and challenges for experimental realization in topological quantum matter.