Topological insulators are expected to exhibit robust edge-state transport protected by time-reversal symmetry, yet experimental conductance often falls below the quantized limit due to intrinsic and interfacial effects. Here, we demonstrate that the orbital character of topological edge states, governed by spin-orbit coupling and edge termination, plays a critical role in electron injection and transport. Using first-principles calculations combined with nonequilibrium Green's function methods, we investigate PbSe nanoribbons as a model system. We identify an orbital filtering mechanism arising from spin-orbital-entangled edge states, where the $j=1/2$ and $j=3/2$ components of the $p$ orbitals obey symmetry-imposed selection rules at the interface. This effect limits conductance even in the absence of disorder; when present, disorder further promotes an interplay between topological edge states and resonant edge-localized states originating from dangling bonds. Our findings highlight the importance of orbital engineering and angular momentum symmetry mismatch in the design of topological devices and call for an examination of interface physics in quantum materials regarding the topological protection.

The coexistence of unconventional high-temperature superconductivity, topological surface states, and strong electronic correlations makes iron-based superconductors a prominent platform for exploring topological superconductivity and Majorana zero modes. Here, we design a novel intergrowth-structured compound, ${\mathrm{LaNa}}_2{\mathrm{Fe}}_4{\mathrm{As}}_4$ (1244-type), by combining uncollapsed tetragonal ${\mathrm{LaFe}}_2{\mathrm{As}}_2$ and NaFeAs. This unique intergrowth structure provides a new route to engineer topological states in iron-based superconductors. Using density functional theory combined with dynamical mean-field theory calculations, we reveal nontrivial band topologies near the Fermi level ($E_F$) in ${\mathrm{LaNa}}_2{\mathrm{Fe}}_4{\mathrm{As}}_4$, hosting both topological insulator (TI) and topological Dirac semimetal states, and giving rise to two sets of Dirac-cone-type surface states on the (001) surface. Strong electronic correlations renormalize the band structure, bringing the topological surface states closer to $E_F$. Moreover, slight electron doping at the Fe sites can further tune the TI surface states to $E_F$, enhancing their experimental accessibility. The intrinsic self-doping and multiband Fermi surface of ${\mathrm{LaNa}}_2{\mathrm{Fe}}_4{\mathrm{As}}_4$ also suggest potential superconductivity. These findings establish ${\mathrm{LaNa}}_2{\mathrm{Fe}}_4{\mathrm{As}}_4$ as a promising candidate for studying topological superconductivity and Majorana zero modes, calling for experimental validation and further exploration of its potential in quantum applications. They also underscore the effectiveness of the intergrowth strategy in optimizing the topological properties of iron-based superconductors.

Samples of Co were grown directly in the ferromagnetic state under equilibrium conditions using a cobalt sulfide flux. Magnetic fields up to 9 T were applied during growth, and isolated Co products exhibit progressively elongated morphologies, from cubes to rectangular rods to needlelike tendrils with poorly defined facets. The degree of elongation of the major axis was found to correlate with magnetic field direction, strength, and gradient. Two-dimensional x-ray diffraction data indicate some level of polycrystallinelike samples, and quantitative analyses (Le Bail and Rietveld) of the one-dimensional data confirm the presence of hcp and fcc phases. The magnetic responses indicate a partial alignment of the magnetic easy axis of the hcp phase along the magnetic field present during growth.

We herein report the successful intercalation of water molecules into the layered honeycomb lattice of $\mathrm{N}{\mathrm{a}}_2\mathrm{C}{\mathrm{o}}_2\mathrm{Te}{\mathrm{O}}_6$, a Kitaev-candidate compound, to obtain the hydrated phase $\mathrm{N}{\mathrm{a}}_2\mathrm{C}{\mathrm{o}}_2\mathrm{Te}{\mathrm{O}}_6·y{\mathrm{H}}_2\mathrm{O}$ ($y\approx 2.4$). Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and Rietveld refinements indicate that crystalline water resides between the cobalt-based honeycomb layers. This insertion of neutral molecules significantly alters the crystal structure, increasing the interlayer spacing and modifying the local bonding environment. Magnetization measurements reveal an antiferromagnetic transition at $T_{\mathrm{N}}\approx 17.2$ K, accompanied by a discernible weak ferromagnetic component. The application of moderate magnetic fields induces a spin-flop reorientation at ${\mu }_{0}H\approx 5.7$ T. The λ-type anomaly and long-range order persist up to 9 T, showing the reconfiguration of the ground state as opposed to its suppression. Heat-capacity analysis reveals the full $2R\text{ln2}$ magnetic entropy expected for two $J_{\mathrm{eff}}=1/2$ moments per formula unit, confirming the pseudospin description. These findings demonstrate that water intercalation is a robust strategy for tuning the magnetic properties of honeycomb lattice materials. Overall, this study highlights neutral-molecule insertion as a promising route toward the discovery and engineering of quantum magnets based on layered transition metal oxides.

The ${\mathrm{La}}_2{\mathrm{CoMnO}}_6$ (LCMO) perovskite has received a lot of attention due to its near-room-temperature magnetodielectric effect. Despite the recent efforts, the mechanism ruling the correlation between its magnetic and dielectric properties is not yet fully understood. In order to address this issue, we conducted a detailed investigation of the coupling between the structural, electronic, and magnetic properties of a polycrystalline LCMO sample. Using magnetic field-dependent x-ray powder diffraction and measurements with a capacitive dilatometer, we show that applying an external magnetic field decreases the unit cell volume, thereby modifying the octahedral distortions. Experiments involving temperature and field-dependent x-ray absorption spectroscopy at the Co-$L_{2,3}$ edges provide further evidence that the spin-orbit interaction of outermost Co $3d$ orbital and the field-induced enhancement of covalence effects are the key contributors to the magnetostrictive effects. From a detailed analysis using multiplet and density functional theory calculations, we propose that the field-induced modulations of the orbital hybridization and the ligand-to-metal charge transfer are responsible for the changes in the dielectric response of LCMO, thus enabling a direct coupling between magnetic, elastic, and dielectric properties in this material.

Synchrotron x-ray diffraction has been used to study the thermal structure evolution in $\mathrm{CuB}{\mathrm{a}}_2\mathrm{C}{\mathrm{a}}_3\mathrm{C}{\mathrm{u}}_4{\mathrm{O}}_{10+\delta }$ (Cu1234), a superconductor which exhibits a high critical temperature $\left({\mathrm{T}}_{\mathrm{C}}\approx 118\mathrm{K}\right)$, high critical current density, and large upper critical magnetic field. The lattice geometry at the nanoscale of this cuprate belongs to the class of natural heterostructures at the atomic limit, like the artificial high ${\mathrm{T}}_{\mathrm{c}}$ superlattices made of interface space charge in Mott insulator units intercalated by metal units. Temperature-dependent lattice parameters reveal a distinct lattice anomaly at ${\mathrm{T}}_{\mathrm{C}}$ characterized by a drop of the $c$-axis and in-plane Cu-O negative thermal expansion below ${\mathrm{T}}_{\mathrm{C}}$. These results are consistent with a multigap scenario and complex networks of multiscale configurations controlling macroscopic superconducting functions in complex perovskites. In the multigap scenario, the lattice reorganization associated with the chemical potential changes could be assigned to the opening of multiple superconducting gaps in different points of the electron momentum space. Evidence for oxygen diffusion is observed at temperatures above 200 K. We construct a phase diagram correlating temperature, the c/a-axis ratio, and in-plane Cu-O strain, identifying regions associated with gaps opening and oxygen diffusion. These findings provide insights into how lattice geometry controls superconductivity to inform the material design of advanced nanoscale superconducting artificial quantum heterostructures.

We have performed a comprehensive electronic characterization of the needle-like single crystal ${\mathrm{YCrB}}_4$ metal boride, prepared by cleavage, characterized using angle-resolved photoemission spectroscopy with a microfocused beam. Our findings reveal the three-dimensional (3D) band structure of ${\mathrm{YCrB}}_4$, with band dispersions closely aligning with the first-principles calculations, confirming it is a topologically trivial insulator with a narrow band gap. Furthermore, a new metallic surface band was observed after cleavage, likely due to a space charge layer of the electron accumulation type. This study highlights the pivotal role of surface phenomena in shaping the electronic structure of ${\mathrm{YCrB}}_4$ and provides insights into the interplay between bulk and surface states, offering a path for exploring its potential applications in surface-sensitive technologies.

Understanding the behavior of materials under irradiation is crucial for the design and safety of nuclear reactors, spacecraft, and other radiation environments. The threshold displacement energy ($E_d$) is a critical parameter for understanding radiation damage in materials, yet its determination often relies on costly experiments or simulations. This work leverages the machine learning-based sure independence screening and sparsifying operator (SISSO) method to derive accurate, analytical models for predicting $E_d$ using fundamental material properties. The models outperform traditional approaches for monoatomic materials, capturing key trends with high accuracy. While predictions for polyatomic materials highlight challenges due to dataset complexity, they reveal opportunities for improvement with expanded data. This study identifies cohesive energy and melting temperature as key factors influencing $E_d$, offering a robust framework for efficient, data-driven predictions of radiation damage in diverse materials.

Josephson junctions manufactured to tight tolerances are necessary components for superconducting quantum computing. Developing precise manufacturing techniques for Josephson junctions requires an understanding of their make-up and robust feedback metrics against which to optimize. Here, we consider complementary techniques and assess what conclusions they allow us to draw about the barriers in junctions. Monte Carlo simulations of barriers show that standard deviations of 15–20% of the total barrier thickness are compatible with our experimental data. Electrical breakdown allows us to probe the weakest points in barriers. Narrowing the distribution of this breakdown provides a promising feedback mechanism for barrier optimisation. Grouping junctions by breakdown voltage allows us to identify sub-ensembles of junctions with different median resistance. Transmission electron microscopy can be used to find average barrier thickness, although we highlight challenges in forming robust conclusions on the distribution of thicknesses in a barrier from these experiments.

We quantitatively investigate the structural and energetic properties of tetragonal, orthorhombic, and two monoclinic polymorphs of ceria-zirconia solid solutions in the ceria-poor region using first-principles density functional theory calculations. While Ce doping visibly leads to a lattice expansion due to longer Ce-O bonds, we find that phase stabilization is primarily governed by the chemical substitution energy, which can be qualitatively rationalized through the relative energies of pure ${\mathrm{ZrO}}_2$ and ${\mathrm{CeO}}_2$ structures. Local structural relaxations nevertheless play a role and depend primarily on the orientation and separation of Ce-Ce pairs. These effects can be interpreted within an iono-covalent screening model, which provides a physical picture of defect interactions and screening efficiency depending on the local defect environment. Our results offer microscopic insights into the mechanisms driving the phase stability and may guide the design of doped oxide materials with tailored properties.

Accurately evaluating configurational integrals for dense solids remains a central and difficult challenge in the statistical mechanics of condensed systems. Here, we present a tensor network approach that reformulates the high-dimensional configurational integral for identical-particle crystals into a sequence of computationally efficient summations. We represent the integrand as a high-dimensional tensor and apply tensor-train (TT) decomposition together with a custom TT-cross interpolation. This approach circumvents the need to explicitly construct the full tensor. We introduce tailored rank-1 and rank-2 schemes optimized for sharply peaked Boltzmann probability densities, typical for identical-particle crystals. When applied to the calculation of internal energy and pressure-temperature curves for crystalline Cu and Ar at high (GPa) pressures, as well as the alpha-to-beta phase transition diagram of Sn, our method accurately reproduces molecular dynamics simulation results using tight-binding, machine learning, hierarchical interacting particle–neural network, and modified embedded atom method potentials,all within seconds of computation time.

Two-dimensional (2D) materials, such as monolayer ${\mathrm{CrI}}_3$, are the focus of much attention because of their unique properties and potential applications in various technological fields. Despite their discovery years ago, there remains significant confusion regarding space group assignments, with disparities reported across well-known 2D material databases and publications. Therefore, accurate determination of space groups is crucial for understanding the intrinsic properties of these materials and optimizing their performance. We use first-principles calculations to systematically investigate the space group of monolayer ${\mathrm{CrI}}_3$ and other 2D materials reported with disparities. From total energy, geometry optimization, and subsequent lattice dynamics computations, we identify common sources of confusion and propose a methodology to resolve these ambiguities. Our results highlight the necessity of integrating computational analyses with symmetry analysis to achieve a correct space group determination of 2D materials. This approach can be beneficial for, e.g., machine learning algorithms that rely on accurate determination of crystal symmetry to identify material properties.

We report the observation of persistent photoconductivity in $n$-type chlorine-doped ${\mathrm{Sb}}_2{\mathrm{Se}}_3$ single crystals, which exhibit free carrier concentrations exceeding ${10}^{16}{\mathrm{cm}}^{-3}$ at room temperature. Illumination with band gap or near-band gap light below $\sim 30\mathrm{K}$ induces photoconductivity that endures for hours after light cessation. This effect is accompanied by a strongly polarized infrared absorption along the covalently bonded $\mathrm{Sb}-\mathrm{Se}$ chains, following a spectral power-law dependence ${\omega }^{-n}$, where $n$ ($2.2-3.2$) depends on sample and illumination conditions, consistent with band-like transport. Both persistent photoconductivity and photoinduced absorption vanish above $\sim 40\mathrm{K}$ due to a thermal barrier of approximately $190\pm 20\mathrm{meV}$. These phenomena are absent in undoped or O- and Sn-doped samples, underscoring the pivotal role of chlorine doping in enabling persistent photoconductivity.

The antiferromagnetic (AFM) materials are distinguished by zero net magnetic moment, high resistance to external magnetic disturbances, and ultrafast dynamic responses. For advancing AFM materials in spintronic and valleytronic applications, achieving spontaneous valley polarization and the anomalous valley Hall effect (AVHE) is pivotal. We predict an A-type AFM monolayer ${\mathrm{Fe}}_2\mathrm{C}{\left(\mathrm{OH}\right)}_2$, which shows a significant spontaneous valley polarization of 157 meV. In A-type AFM ordered ${\mathrm{Fe}}_2\mathrm{C}{\left(\mathrm{OH}\right)}_2$, spatial inversion symmetry ($P$) and time-reversal symmetry ($T$) are individually broken, yet the combined $PT$ symmetry is preserved. This symmetry conservation leads to spin degeneracy, resulting in zero Berry curvature in the momentum space and absence of AVHE. However, a layer-locked hidden Berry curvature is produced, leading to the observation of the valley layer-spin Hall effect. Further, an external out-of-plane electric field can induce spin splitting by introducing layer-dependent electrostatic potential, enabling the layer-locked AVHE. Additionally, the introduction of a built-in electric field caused by the Janus structure also induces spin splitting in monolayer ${\mathrm{Fe}}_2\mathrm{C}\left(\mathrm{OH}\right)\mathrm{F}$ due to the electric-potential-difference-AFM mechanism. The high out-of-plane magnetic anisotropy and realization of AVHE, offer promising opportunities for next-generation spintronic technologies.

Creation and manipulation of magnetic domain walls (DWs) are a core subject of research in developing prototype devices for spintronic applications. DWs can be created artificially and moved by applying either a magnetic field or an electric current, as has been extensively investigated. Here, we study the DW pinning and depinning in half-metallic ferromagnetic ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_3$ nanostructures with a notch that is about 90% of the width of the wire. By measuring the magnetoresistance of the notched wires while sweeping the magnetic field, we unambiguously observe DW pinning and depinning from 10 to 300 K. Analysis of the temperature dependence reveals that both $\mathrm{\Delta }R$ (the DW resistance) and $\mathrm{\Delta }R/R_0$ ($R_0$ is the resistance at zero field) are proportional to the temperature. The DW resistivity is calculated to be of the order of ${10}^{-17}\mathrm{\Omega }{\mathrm{m}}^2$ at 10 K and ${10}^{-15}\mathrm{\Omega }{\mathrm{m}}^2$ at 300 K. The latter value agrees with the reported intrinsic DW resistivity in films. In addition, we find approximately constant $\mathrm{\Delta }R$ and $\mathrm{\Delta }R/R_0$ for widths from 5 down to $1.8\mu \mathrm{m}$ and a pronounced increase in both quantities when the width goes down to 755 nm. With the extracted magnetocrystalline anisotropy parameters from the measurements of the remanent magnetization and the magnetic torque as function of angle of the magnetic field with respect to the substrate normal, we further perform micromagnetic simulations and obtain results consistent with the experimental data. Our work may promote designing relevant prototypes and may constitute a platform to explore the effect of spin torque transfer on DWs.

We investigate how magnetic fields affect the quadrupolar domains in the $5d$ transition-metal oxide ${\mathrm{Ba}}_2{\mathrm{MgReO}}_6$ (BMRO), which crystallizes in the double-perovskite structure. At $T_{\mathrm{q}}=33$ K, BMRO undergoes a quadrupolar-order transition, resulting in a cubic-to-tetragonal structural change, followed by a magnetic transition to a canted antiferromagnetic phase at $T_{\mathrm{m}}=18$ K. These transitions cause the formation of three types of tetragonal domains below $T_{\mathrm{q}}$ and four types of magnetic domains for each tetragonal domain below $T_{\mathrm{m}}$. One tetragonal domain is preferred when the magnetic field is applied along the cubic [1 1 0] direction, and its volume fraction exceeds 80% at 10 K. The magnetic-field direction has a significant impact on domain selection. It is revealed that a magnetic field induces not only magnetic but also structural domain switching via unique spin–lattice coupling in the spin–orbit-entangled quadrupolar-order state in BMRO.

Thermoelectric materials, which can convert waste heat to electricity or be utilized as solid-state coolers, hold promise for sustainable energy applications. However, optimizing thermoelectric performance remains a significant challenge due to the complex interplay between electronic and thermal transport properties. In this work, we systematically optimize $ZT$ in graphene antidot lattices (GALs), nanostructured graphene sheets with periodic nanopores characterized by two geometric parameters: the hexagonal unit cell side length $L$ and the antidot radius $R$. The lattice thermal conductivity is determined through machine-learned potential-driven molecular dynamics (MD) simulations, while electronic transport properties are computed using linear-scaling quantum transport in combination with MD trajectories based on a bond-length-dependent tight-binding model. This method is able to account for electron-phonon scattering, allowing access to diffusive transport in large-scale systems, overcoming limitations of previous methods based on a nonequilibrium Green's function formalism. Our results show that the introduction of the antidots effectively decouples lattice and electronic transport and leads to a favorable and significant violation of the Wiedemann-Franz law. We find that optimal $ZT$ values occur in GALs with intermediate $L$ and $R$, closely correlated with peak power factor values. Notably, thermoelectric performance peaks near room temperature, with maximal $ZT$ values approaching 2, highlighting GALs as promising candidates for high-performance thermoelectric energy conversion.

The ability of materials to convert charge current into spin current is fundamental to many spintronics applications. One means of realizing this conversion is via Rashba-Edelstein effect (REE). Using density functional theory simulations, we predict that REE can be induced in the recently discovered family of semiconducting ferroelectrics, $\mathrm{CsGe}{X}_3$ $(X=\mathrm{I}, \mathrm{Br}, \mathrm{Cl})$. The effect is quantified through Rashba-Edelstein coefficients, ${\chi }_{xy}=-{\chi }_{yx}$, which are nonzero in valence and conduction bands. The largest values, obtained for ${\mathrm{CsGeI}}_3$, are $3.45\times {10}^{10}$ $\frac{\hslash }{\mathrm{A}\mathrm{cm}}$ and $0.97\times {10}^{10}$ $\frac{\hslash }{\mathrm{A}\mathrm{cm}}$ in the conduction and valence bands, respectively. The values are comparable to, and sometimes exceed, those of other inorganic materials, although the maximal values occur away from the band edges. The coefficients' sign couples to the direction of spontaneous polarization, offering opportunities for nonvolatile spin current manipulation via external electric field. Furthermore, these coefficients are highly tunable through strain engineering owing to strain-induced variations in spin textures and energy isosurfaces. Specifically, $\chi$ in the valence band of ${\mathrm{CsGeI}}_3$ is enhanced to $3.61\times {10}^{10}$ $\frac{\hslash }{\mathrm{A}\mathrm{cm}}$ under 5% biaxial strain. Given this potential, we synthesized ${\mathrm{CsGeI}}_3$ to validate our simulation structure and found excellent agreement between experiment and simulation, thereby allowing extrapolation of our findings to practically significant temperatures. Our study identifies promising materials for nonvolatile, multifunctional spintronic applications.