We have investigated the structural, magnetic, and transport characteristics of single-phase polycrystalline ${\mathrm{Er}}_2{\mathrm{Cu}}_2\mathrm{In}$. ${\mathrm{Er}}_2{\mathrm{Cu}}_2\mathrm{In}$ adopts a tetragonal structure reminiscent of ${\mathrm{Mo}}_2{\mathrm{B}}_2\mathrm{Fe}$-type, with a space group of $P4/mbm$ (No. 127). Below a critical temperature (${\mathrm{T}}_{\mathrm{C}}$) of 41 K, we have confirmed long-range ferromagnetic (FM) ordering through dc magnetization, specific heat capacity, and electrical resistivity. The temperature-dependent ac-magnetic susceptibility under varying excitation frequencies and ac-driven fields has shown the existence of a spin glass state below the FM transition temperature. We have employed a combination of methods, including Vogel-Fulcher, Arrhenius activation, and critical-scaling approaches, to analyze the ac-magnetic susceptibility data and estimate the dynamical parameters governing spin dynamics in ${\mathrm{Er}}_2{\mathrm{Cu}}_2\mathrm{In}$. Furthermore, the magnetoresistance exhibits significant variations around the FM transition temperature, indicative of the rich and intricate magnetic behavior inherent to ${\mathrm{Er}}_2{\mathrm{Cu}}_2\mathrm{In}$.

Surface-functionalized two-dimensional (2D) materials have garnered considerable interest owing to their emergent functional properties, including catalytic activity, ferroelectricity, and superconductivity. Here, based on first-principle calculations, we demonstrate that selenium functionalization effectively induces superconductivity in the nonsuperconducting $H$-type ${\mathrm{Mo}}_2\mathrm{B}$ ($H\text{−}{\mathrm{Mo}}_2\mathrm{B}$) monolayer. Three distinct and stable selenized MBene phases—denoted as $H_1$-, $H_2$-, and $H_3\text{−}{\mathrm{Mo}}_2{\mathrm{BSe}}_2$—are systematically identified. The incorporation of selenium significantly elevates the density of states at the Fermi level and strengthens the electron-phonon coupling (EPC). The computed EPC constants $\lambda$ for $H_1$-, $H_2$-, and $H_3\text{−}{\mathrm{Mo}}_2{\mathrm{BSe}}_2$ are 1.04, 0.73, and 1.32, respectively, yielding superconducting transition temperatures ($T_c$) of 17.80, 6.64, and 17.56 K. In addition, a nonzero topological invariant (${\mathbb{Z}}_2$ = 1) and clearly observable edge states collectively evidence nontrivial band topology in selenized ${\mathrm{Mo}}_2\mathrm{B}$ monolayer. These findings not only establish surface functionalization as an effective strategy for activating superconductivity in $H\text{−}{\mathrm{Mo}}_2\mathrm{B}$, but also position the Se-functionalized system as a compelling candidate for investigating the interplay between superconductivity and topological states in 2D materials.

We investigate the strain response of underdoped ${\mathrm{HgBa}}_2{\mathrm{CuO}}_{4+\delta }$ (Hg1201), by synchrotron X-ray diffraction and corresponding simulations of thermal diffuse scattering. The compression in the crystallographic $a$ direction leads to relatively small expansion in the $b$ and $c$ directions, with Poisson ratios ${\nu }_{\mathrm{ba}}=0.16$ and ${\nu }_{\mathrm{ca}}=0.11$, respectively. However, the Cu-O distance in the $c$ direction exhibits a notable 0.9% increase at 1.1% $a$-axis compression. We further find strain-induced diffuse scattering that corresponds to a new type of two-dimensional charge correlation. Interestingly, this signal is insensitive to the onset of superconductivity and instead corresponds to a short-range, nearly commensurate modulation with a wave vector close to (0.5,0,0) and a correlation length of approximately 4 unit cells. It closely resembles the charge order theoretically predicted in the phase diagram of the spin-liquid model with resonating valence bonds on a square lattice.

Quantum two-level systems (TLSs) commonly found at low temperature in amorphous and disordered materials are responsible for decoherence in superconducting Josephson junction qubits particularly because they absorb energy of coherent qubit oscillations in the microwave frequency range. In planar Josephson resonators with oxide interfaces, this absorption is characterized by an anomalously weak loss-tangent dependence on the field in the nonlinear regime that conflicts with the theoretical expectations and the observations in amorphous dielectrics. It was recently suggested that this anomalous absorption is caused by TLS dynamic interactions. Here, we show that such interactions cannot lead to the observed loss-tangent field dependence and suggest the alternative explanation assuming that TLS dipole moments $p$ are distributed according to the specific power law $P\left(p\right)\propto 1/p^{3-\eta }$ ($0\le \eta <1$). This assumption, indeed, results in the observed loss-tangent behavior. The hypothesis of a power-law distribution is supported both by the recent measurements of individual TLS dipole moments and the theoretical model of TLS formation because of the long-range dipole-dipole interaction, thus connecting the anomalous absorption with the possible solution of the longstanding problem of the nature of TLSs.

The non-Hermitian skin effect (NHSE) has prominently emerged in non-Hermitian systems, leading to a plethora of unique features without Hermitian counterparts. However, the characterization of NHSE in many-body dynamics remains elusive. Here we present an algebraic framework to comprehensively characterize the entanglement entropy and correlation of the steady state in many-body dynamics in the presence of the NHSE, with the methods from graph theory. We show that the NHSE can induce nontrivial correlation clustering in the many-body steady state. By interpreting pairwise mutual information or correlation in the steady state as a weighted graph, we reveal latent community structures. The quantum criticality associated with the NHSE is well captured by analyzing the modularity and centrality of the correlation network extracted from the steady state. We verify our approach by the application to several prototypical models, and successfully reproduce the phase diagrams. Our work suggests a direct and universal characterization of the long-time many-body dynamics, and offers an alternative perspective of studying the NHSE in non-Hermitian systems.

Exactly solvable dissipative models provide an analytical tool for studying the relaxation dynamics in open quantum systems. In this work, we study an exactly solvable model based on an anisotropic variant of the Yao-Lee spin-orbital model, with dissipation acting in the spin sector. We map Liouvillian dynamics to fermions hopping in a doubled Hilbert space under a non-Hermitian Hamiltonian and demonstrate the model's exact solvability. We analyze the model's strong and weak symmetries, which protect an exponentially large manifold of nonequilibrium steady states, establishing the system as a physically feasible dissipative spin liquid. Furthermore, we analyze the transient dynamics in a translationally invariant sector and discover that the single-particle Liouvillian spectrum hosts an exceptional ring in momentum space. We map out a characteristic $\mathcal{P}\mathcal{T}$ symmetry-breaking transition driven by the dissipation strength, which governs the crossover from oscillatory to decaying relaxation of physical observables. Our work provides a physically motivated, solvable setting for exploring the coexistence of dissipative spin-liquid physics and Liouvillian spectral singularities.

Contrary to conventional wisdom that spin dynamics induced by current are exclusive to metallic magnets, we theoretically predict that such phenomena can also be realized in magnetic insulators, specifically in the magnetoelectric antiferromagnet ${\mathrm{Cr}}_2{\mathrm{O}}_3$. We reveal that the displacement current driven by the terahertz electric field is able to generate a Néel spin-orbit torque in this insulating system. By introducing an alternative electric dipole order parameter, i.e., the antiferroelectric vector, arising from the dipole moment at ${\mathrm{Cr}}^{3+}$ sites, we combine symmetry analysis with a Lagrangian approach and uncover that the displacement current couples to the antiferromagnetic spins and enables ultrafast control of antiferromagnetic order. The derived equations of motion show that this effect competes with the linear magnetoelectric response, offering an alternative pathway for manipulating antiferromagnetic order in insulators. Our findings establish insulator antiferromagnets as a viable platform for electric-field-driven antiferromagnetic spintronics and provide general design principles for nonmetallic spin-orbit torque materials.

${\mathrm{LaCrGe}}_3$ has become a playground to understand quantum critical phenomena in ferromagnetic (FM) materials. It has also garnered attention due to its peculiar two FM phases. Here, we demonstrate the presence of these phases using the Hall effect. Continuous temperature-dependent Hall resistivity measurements at fixed magnetic fields clearly demonstrate the presence of these phases, regardless of the direction of the applied magnetic field. The remanent Hall resistivity and Hall coefficient undergo a maximum and a minimum, respectively, at the boundary between the two phases. We observe a significantly large anomalous Hall conductivity of 1160 ${\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$ at 2 K when the magnetic field is applied along the magnetic easy axis, which is dominated by intrinsic effects, at least in the low-temperature FM phase. In the paramagnetic (PM) phase, hexagonal ${\mathrm{LaCrGe}}_3$ exhibits opposite charge carrier polarities along different crystallographic directions, attributed to the anisotropic Fermi surface geometry, a phenomenon known as “goniopolarity”. The coexistence of goniopolar transport and unconventional magnetic phases may lead this material as a promising candidate for future electronic devices.

We investigate the impact of the quantum effects of protons on the electronic structure of high-pressure ${\mathrm{H}}_3\mathrm{S}$, a benchmark hydrogen-rich superconductor with a critical temperature $\left(T_c\right)$ exceeding 200 K. Using nuclear-electronic orbital density functional theory (NEO-DFT), we treat hydrogen nuclei quantum mechanically on the same footing as electrons within a first-principles framework. Our calculations reveal that nuclear quantum effects (NQEs) induce subtle modifications to the electronic band structure and density of states (DOS) near the Fermi energy, including features associated with van Hove singularities. However, the resulting changes in the DOS would increase $T_c$ by only a few percent. On the other hand, calculations of the phonon dispersion with the NEO-DFT method show large changes in the hydrogen-dominated phonons that arise from a stiffening of the S-H bonds due to NQEs. These findings imply that the experimentally observed reduction in $T_c$ upon deuteration arises predominantly from changes in the phonon properties while NQEs-induced modifications to the electronic structure itself are minimal.

Polaronic states widely exist in transition metal oxides and play important roles in various catalytic processes. However, the fundamental mechanism of how polarons affect the catalysis remains unclear. In this paper, we take the process of adsorption and dissociation of water on the rutile ${\mathrm{TiO}}_2$(110) surface as an example, and investigate the nature of adsorbate-polaron interaction based on density functional theory. The dissociation of water is suppressed both thermodynamically and kinetically if it is the nearest neighbor to the polaron. The underlying mechanism is clarified to be generic due to the coupling between the polaronic state and the specific frontier orbitals of the adsorbates. A linear relation is established between the dissociation energy and dissociation barrier, the slope of which is higher on the surface with excess hole than on that with excess electron, whereas the dissociation energy on a specific site is determined by the relative coupling strength of the doped charge with the frontier orbitals of the adsorbate. These findings can provide a theoretical foundation for material engineering to improve the catalysis efficiency of transition metal oxides.

Polarization engineering has played an important role in advancing III-nitride semiconductor devices over recent decades. However, the exact magnitude and orientation of polarization remain highly debated, as significant discrepancies persist among different theoretical approaches and experiments. Therefore, we combine off-axis electron holography with surface potential calibration and self-consistent electrostatic modeling to directly measure quantitatively polarization changes at ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}/\mathrm{GaN}$ interfaces. The results reveal a pronounced nonlinear, cubic dependence of spontaneous polarization on indium composition responsible for theoretical overestimation of polarization changes. Moreover, we show that only a layered hexagonal reference phase, rather than the zinc-blende phase, provides an accurate description of the experimental bowing of spontaneous polarization and hence a consistent theoretical framework of polarization in group-III nitrides. These results reconcile experiment and theory and provide a reliable basis for polarization engineering in InGaN alloys.

Generating spin-mixed edge states with hybridized spin-up and spin-down components and clarifying their transport mechanisms are critical to topological spintronic and valleytronic devices. In this work, we propose two types of spatially modulated Haldane-Rashba models that incorporate spatial variation of both the Haldane term and the extrinsic Rashba effect, aiming at generating spin-mixed edge states. For one model type with modulation directed inward from the system boundaries, two chiral edge states (CESs) and four antichiral edge states (AESs) can be induced, which are attributed to the coupling between bulk states of pristine graphene and inner edge states characterized by the Chern number difference between the two adjacent topological domains. Based on a similar mechanism, the other model type with modulation directed outward from the central system interface, yields two valley-dependent CESs and two valley-dependent AESs. To explore the transport behavior of these states and the underlying mechanism, we derive the corresponding expressions for conductance and local bond current of these edge states in zigzag graphene nanoribbons. Our results demonstrate that the general expressions of conductance and local bond current enable the calculation of spin-conserved and spin-flipping transport properties involving valley scattering, applicable to both these spin-mixed edge states and other types of edge states. In this work, we not only provide a theoretical foundation for exploring the transport properties of spin-mixed edge states but also offer a promising platform for their realization and engineering, thereby jointly advancing the design of topological spintronic and valleytronic device technologies.

Bilayer metagratings with asymmetric structural parameters could host unidirectional guide resonances. The distribution of unidirectional guide resonances in the space of structural parameters and synthetic parameters is identified. As the incident optical beam is resonant with the unidirectional guide resonance, the Goos-Hänchen shifts of the scattered beams exhibit two anomalous behaviors: The resonant peak of the Goos-Hänchen shift is accompanied by constant transmittance and reflectance, and the magnitude of the Goos-Hänchen shift is not always proportional to the quality factor of the unidirectional guide resonance. The temporal coupled mode theory analysis reveals that the first anomalous behavior is due to interference between direct scattering and radiation from the unidirectional guide resonance; the Goos-Hänchen shifts are proportional to the group velocity as well as the quality factor of the unidirectional guide resonance. Numerical simulations of the incidence of the Gaussian beam with finite beamwidth provide intuitive visualization of the Goos-Hänchen shift.

Kagome lattices facilitate various quantum phases, yet in bulk materials, their kagome flat bands often interact with bulk bands, suppressing kagome electronic characteristics for hosting these phases. Here, we use density functional theory calculations to predict the geometric and electronic structures as well as the topological and magnetic properties of a series of $\mathrm{MoT}{\mathrm{e}}_{2-x}$ kagome monolayers formed by mirror-twin-boundary (MTB) loops. We analyze 13 MTB-loop configurations of varying sizes and arrangements to assess their impacts on various properties. Within the intrinsic band gap of $\mathrm{MoT}{\mathrm{e}}_2$, we identify two sets of kagome bands, primarily originating from in-plane and out-of-plane Mo $d$ orbitals at MTB-loop edges and vertices, respectively. Four configurations exhibit superior stability in certain ranges of Te chemical potentials, respectively, while others show comparable stability. Among these configurations, four display band gaps and potentially nonzero $Z_2$ topological invariants, suggesting possible topological phases, while the remaining two are metallic and feature Stoner magnetization. These findings guide the design of kagome-based two-dimensional materials with tunable electronic, topological, and magnetic properties.

Low-dimensional quantum magnets, particularly highly frustrated ones, exhibit strong spin fluctuations, which can be probed via nuclear magnetic resonance (NMR). However, numerical simulations of NMR relaxation rates, like the spin-lattice relaxation rate $1/T_1$, remain challenging for the real-time evolution or analytical continuation. Here we develop an imaginary-time approach for computing $1/T_1$ using thermal tensor networks (thermoTNs). We demonstrate the accuracy and versatility of the method by applying it to one-dimensional chain and two-dimensional lattice models. Our results show that the critical exponents $\eta$ and $z\nu$ can be extracted from the low-temperature scaling behaviors of simulated $1/T_1$ data near the quantum critical points. We subsequently employ this method to investigate three representative quantum magnets: the Ising chain compound ${\mathrm{CoNb}}_2{\mathrm{O}}_6$, and the triangular-lattice quantum antiferromagnets ${\mathrm{Ba}}_8{\mathrm{CoNb}}_6{\mathrm{O}}_{24}$ and the ${A\mathrm{YbSe}}_2$ series ($A=$ Na, K, Cs). On triangular lattice, the simulated $1/T_1$ data clearly track the transition from spin-ordered states to quantum spin liquids (QSLs), highlighting NMR relaxation rate as a sensitive probe for QSL in these actively studied systems. Moreover, the approach can be extended to transport properties like the thermal conductivity, by substituting relevant operators. We show that thermoTN, equipped with imaginary-time proxies, serves as a powerful and sensitive tool for simulating equilibrium and nonequilibrium phenomena in frustrated quantum magnets and correlated systems in general.

Minimal Kitaev chains provide a unique platform to engineer Majorana states in quantum dots interacting via normal tunneling and crossed Andreev reflection specified by their amplitudes $|{\eta }_{n,a}|$. Here we analyze fluctuations of electric currents in a double quantum dot Kitaev chain using the differential effective charge $q$, that is the ratio of the differential shot noise and conductance. At low bias voltages $V$ we find that $q=e/2$ in a very narrow vicinity of the point $|{\eta }_n|=|{\eta }_a|$ whereas $q=3e/2$ almost in the whole sweet spot region and marks the range where the poor man's Majorana states largely govern the fluctuations. At high $V$ we show that the sweet spot region is still characterized by $q=3e/2$ uniquely identifying the poor man's Majorana states using the high voltage tails. For $|{\eta }_n|=0$ or $|{\eta }_a|=0$ we obtain $q=e$ at any $V$. Remarkably, before the asymptotic value $q=e$ is reached for very high $V$, the maximal value $q=2e$ is formed at $\left|eV\right|=2\sqrt{|{\eta }_n{|}^2+{\left|{\eta }_a\right|}^2}$. The unique nature and potentially rich fluctuation behavior revealed in this work provide a stimulating ground for the next generation experiments on nonequilibrium shot noise in minimal Kitaev chains.

Materials combining electrically switchable ferroelectricity and tunable topological states hold significant promise for advancing both fundamental quantum phenomena and practical device architectures. Here, we employ first-principles calculations to systematically investigate the sliding ferroelectricity-mediated topological transitions in bilayer $M{\mathrm{Bi}}_2{\mathrm{Te}}_4$ ($M=\mathrm{Ge},\mathrm{Sn},\mathrm{Pb}$) systems. By systematically engineering interlayer sliding configurations with oppositely polarized states, we demonstrate the emergence of reversible band inversion accompanying with topological phase transitions. The obtained topologically nontrivial band gaps can reach up to 31 meV (${\mathrm{GeBi}}_2{\mathrm{Te}}_4$), 36 meV (${\mathrm{SnBi}}_2{\mathrm{Te}}_4$), and 35 meV (${\mathrm{PbBi}}_2{\mathrm{Te}}_4$), respectively, enabling the room-temperature observation of the quantum spin-Hall effect. In particular, these systems exhibit substantial out-of-plane ferroelectric polarization of about 0.571–0.623 pC/m. Two independent signatures unambiguously confirm the topological nontriviality: (i) the resulting $Z{}_2$ topological invariant ${\mathbb{Z}}_2=1$, and (ii) the emergence of gapless helical edge states spanning the bulk insulating gap. This synergy arises from the unique sliding-induced charge redistribution mechanism, which simultaneously modulates the interlayer interaction and breaks the out-of-plane inversion symmetry. The coengineering of nonvolatile ferroelectric switching and topologically protected conduction channels in $M{\mathrm{Bi}}_2{\mathrm{Te}}_4$ bilayers establishes a material paradigm for designing reconfigurable quantum devices, where electronic topology can be electrically controlled via polarization reversal. Our study provides critical insights in manipulating quantum states in van der Waals ferroelectrics for multifunctional nanoelectronics.

We investigate the second-order Rényi entanglement entropy at the quantum critical point of a spin-1/2 antiferromagnetic Heisenberg model on a columnar dimerized square lattice. The universal constant $\gamma$ in the area-law scaling $S_2\left(\ell \right)=\alpha \ell -\gamma$ is found to be sensitive to the entangling surface configurations, with ${\gamma }_{\text{sp}}>0$ for strong-bond-cut (special) surfaces and ${\gamma }_{\text{ord}}<0$ for weak-bond-cut (ordinary) surfaces, which is attributed to the distinct conformal boundary conditions. Introducing boundary dimerization drives a renormalization group (RG) flow from the special to the ordinary boundary criticality, and the constant $\gamma$ decreases monotonically with increasing dimerization strength, demonstrating irreversible evolution under the boundary RG flow. These results provide numerical evidence for a higher-dimensional analog of the $g$ theorem, and suggest $\gamma$ as a possible characteristic function for boundary RG flow in ($2+1$)-dimensional conformal field theory.