The identification of topological Weyl semimetals has recently gained considerable attention. Here, we report the results of density-functional theory calculations regarding the magnetic properties, the electronic structure, and the intrinsic anomalous Hall conductivity of the title compound, which was synthesized already 50 years ago but received little attention until now. We found ${\mathrm{Cs}}_2{\mathrm{Co}}_3{\mathrm{S}}_4$ to be a ferrimagnetic half-metal with a total spin magnetic moment of about $3{\mu }_B$ per formula unit. It shows an energy band gap of 0.36 eV in the majority-spin channel and a pseudogap at the Fermi level in the minority-spin channel. We identified several sets of low-energy Weyl points and traced their dependence on the direction of magnetization. The intrinsic anomalous Hall conductivity is predicted to reach a magnitude of up to 500 ${\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$, which is comparable to values obtained in other celebrated Weyl semimetals.

The local arrangement of atoms in an alloy impacts its electronic band structure and, consequently, its fundamental physical properties. This work investigates the short-range order of tin atoms in binary $\mathrm{G}{\mathrm{e}}_{1-x}\mathrm{S}{\mathrm{n}}_x$ semiconductors epitaxially grown on Ge-buffered Si (001) substrates. Samples featuring Sn content up to 13 at.% were analyzed by x-ray absorption fine structure spectroscopy at the Sn-K edge. The study reveals how the growth method and its process parameters, like temperature, or the epitaxial built-up strain affect the local atomic ordering of tin within the alloys. While the deposition technique seems to have a marginal effect on the Sn short-range ordering, the growth temperature and Sn content systematically influence the bonding angles Sn. Ge-Sn next neighbor coordination shells, whereas the interatomic distances remain largely unaffected. In the first coordination shell Sn-Ge are strongly favored over Sn-Sn, while the opposite happens in the next coordination shell, where Sn-Sn are systematically favored. These insights into the relationship of growth condition and layer properties enable to identify the nature of the large variety of electronic and optical properties measured in $\mathrm{G}{\mathrm{e}}_{1-x}\mathrm{S}{\mathrm{n}}_x$ layers.

High-entropy alloy superconductors represent a unique blend of advanced material systems and quantum physics, offering significant potential for advancing superconducting technologies. In this study, we report a detailed theoretical and experimental investigation of high-entropy alloy superconductors ${\mathrm{Ta}}_{0.2}{\mathrm{Nb}}_{0.2}{\mathrm{V}}_{0.2}{\mathrm{Ti}}_{0.2}{X}_{0.2}$ ($X=\mathrm{Zr}$ and Hf). Our study unveils that both the materials crystallize in a body-centered-cubic structure (space group: Im-3m) and exhibit bulk superconductivity with a superconducting onset temperature of ($T_c^{\text{onset}}$) of 5 K for $X=$ Hf and 6.19 K for $X=\mathrm{Zr}$ sample. Our detailed analysis, including magnetization, resistivity, heat capacity measurements, and density functional $X=\mathrm{Zr}$ theory (DFT) calculations indicates moderately coupled isotropic $s$-wave superconductivity in these materials. Our DFT results find significant spectral weight at the Fermi energy and phonon spectra is free of imaginary modes, confirming the dynamical stability and metallic nature of these alloys. Remarkably, we have observed a high upper critical field $\left[H_{c2}\left(0\right)\right]$ surpassing the Pauli paramagnetic limit for the $X=$ Hf sample and explained it on the basis of the increased spin-orbit coupling in the structure. ${\mathrm{Ta}}_{0.2}{\mathrm{Nb}}_{0.2}{\mathrm{V}}_{0.2}{\mathrm{Ti}}_{0.2}{\mathrm{Zr}}_{0.2}$, on the other hand, shows a conventional $H_{c2}$ behavior. With the dynamical stability of these alloys, excellent normal state metallic nature, high microhardness, and high upper critical field, these samples emerge as potential candidates for future applications in superconducting devices.

Compared to semiconductor quantum wells, systems where the quantum well layer is a metal have received relatively little attention. Here, we investigate an asymmetric metal quantum well that naturally forms when single-crystal metallic Al is epitaxially grown on Si (111) and then exposed to air, forming a passivating oxide layer. We report on the first-principles calculations of the ${\mathrm{Al}}_2{\mathrm{O}}_3$-Al-Si heterostructure and discuss the band alignment across it. The calculated valence band offsets are in good agreement with our photoemission measurements and can be understood within the metal-induced gap states picture. The confined metallic well states from ab initio calculations are also in good agreement with previously published ARPES results.

Recently, we introduced the screened-exchange range-separated hybrid (SE-RSH) functional to account for spatially dependent dielectric screening in complex materials. The SE-RSH functional has shown good performance in predicting the electronic properties of a large variety of semiconductors and insulators, and of heterogeneous systems composed of building blocks with large dielectric mismatch. Here, we assess the performance of SE-RSH for oxide materials, including antiferromagnetic transition-metal oxides. Through a comparison with other dielectric-dependent hybrid functionals, we demonstrate that SE-RSH yields improved predictions of dielectric constants and band gaps, bringing them into a closer agreement with experimental values. The functional also provides accurate values of magnetic moments of several oxides.

Elemental substitution plays a crucial role in atomic-scale design of two-dimensional (2D) magnetic materials, such as Janus monolayers. In this work, we report that 1T'α-$\text{CrS}X$ $(X=\mathrm{Cl},\mathrm{Br},\mathrm{I})$ monolayers, where halogen atoms intermittently substitute double sulfur lines within the layer, are the most energetically favorable structures of the half-halogen-substituted trigonal $\mathrm{Cr}{\mathrm{S}}_2$ monolayers. Our findings indicate the CrSCl monolayer is doubly striped antiferromagnetic, and the CrSBr and CrSI monolayers are ferromagnetic. Their transition temperatures are estimated to reach up to 166 K via Monte Carlo simulations. Furthermore, it is found that the magnetic ground states of all these three monolayers can be easily tuned by applying uniaxial strains in the range of –3% to 2% along the $x$ direction. Our study offers new insights into the discovery and synthesis of switchable 2D chromium-based magnetic materials.

A dielectric zirconia metasurface for resonant polarization conversion at microwave frequencies is theoretically and experimentally investigated. The metasurface is composed of a periodic array of square slotted rings interrupted by solid bridge sectors that provide interconnection and mechanical stability to the free-standing metasurface structure. Moreover, they selectively break the symmetry of the unit cell, thus allowing for polarization conversion based on both weakly and strongly resonant modes, the latter stemming from bound states in the continuum. The main findings of the theoretical analysis are corroborated through the experimental characterization of a metasurface sample fabricated by a recently introduced three-dimensional (3D) printing technique based on fused filament fabrication. Going beyond the target application of resonant polarization conversion, this work proposes an approach for the realization of high-permittivity, 3D-printed zirconia metasurfaces with submillimeter features for strong wave-matter interaction at microwave frequencies.

Potassium tantalate ${\mathrm{KTaO}}_3$ is a cubic, paraelectric perovskite ceramic that exhibits surprising ductility at room temperature as most recently reported. Much like strontium titanate (${\mathrm{SrTiO}}_3$), plastic deformation is accommodated by dislocations gliding in $\left\{110\right\}$ planes. In this work, we propose a new interatomic potential for ${\mathrm{KTaO}}_3$, and apply it to model dislocations with $\langle 110\rangle$ Burgers vector. We demonstrate that dislocations dissociate, and finely characterize their core structure and Peierls potential. Dislocations of edge character can carry a positive or negative electric charge, but we show that charge-neutral configurations are energetically more favorable. We also perform high-resolution electron microscopy to validate our simulation methodology. Comparing our results with other ductile perovskites, we confirm ${\mathrm{KTaO}}_3$ to be ductile, but stiffer than ${\mathrm{SrTiO}}_3$.

Topological insulators have been intensively studied over the past few decades. Among these materials, three-dimensional (3D) zirconium pentatelluride (${\mathrm{ZrTe}}_5$) stands out as one of the most intriguing due to its ability to encompass a wide range of distinct topological phases. However, identifying a topological phase in ${\mathrm{ZrTe}}_5$ has proven challenging. Despite extensive studies, experimental and theoretical findings have only revealed facets of its extended topological properties, making a coherent understanding of this exotic material elusive. In this work, we employ density functional theory to study the electronic structure and quantum oscillations exhibited by various topological phases of 3D bulk ${\mathrm{ZrTe}}_5$. By analyzing patterns in band structures, Fermi surfaces, and Shubnikov-de Haas (SdH) oscillations, we can distinguish topological phases without performing conventional calculation of topological invariants or boundary state contributions. We find that the Fermi pockets of weak topological insulators and Dirac semimetal phases take the form of a 3D nonuniform ellipsoid, while the strong topological insulator phase is distinguishable by a pair of symmetric Fermi pockets. This approach enables the identification of topological phases in ${\mathrm{ZrTe}}_5$ by measuring quantum oscillations. Overall, we believe that our analysis of changes in Fermi pockets and the associated topological phase transitions can be extended to other materials and serve as a valuable tool for identifying topological phases.

We investigate the structural and magnetic properties of $\mathrm{Ba}{\mathrm{Ni}}_3{\left(\mathrm{As}{\mathrm{O}}_4\right)}_2{\left(\mathrm{OH}\right)}_2$, focusing on its spin-1 kagome lattice and the intricate coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) interactions. Powder x-ray diffraction analysis confirms a highly crystalline trigonal structure. Detailed Rietveld refinement identifies a single crystallographic Ni site, indicative of a perfect kagome lattice. Magnetic susceptibility measurements suggest predominantly ferromagnetic interactions with an effective magnetic moment consistent with $\mathrm{N}{\mathrm{i}}^{2+}$ spins, yet the system undergoes AFM ordering at a Néel temperature of 5.8 K. Isothermal magnetization measurements reveal a series of metamagnetic transitions culminating in a plateaulike phase near $\frac{1}{3}$ of the total saturation magnetization. Analysis of the phase boundaries shows that the AFM phase supports a substantial net moment in each kagome layer, comparable with that of the $\frac{1}{3}$ plateau. This observation challenges the conventional model—where a ${120}^{\circ }$ ground state transitions to an up-up-down configuration—commonly assumed for kagome AFMs. Instead, our findings indicate that both the zero-field ground state and the field-induced phases exhibit in-plane ferrimagnetic spin arrangements on the kagome lattice, with the metamagnetic transition corresponding to a shift from layer-by-layer AFM aligned net moments to FM aligned ones. This configuration is stabilized by bond frustration, a network of competing interactions that can favor both FM and AFM couplings, highlighting the essential role of frustration in governing the low-temperature magnetic behavior of spin-1 kagome systems. By moving beyond the canonical ${120}^{\circ }$ paradigm, these results expand the landscape of unconventional magnetic phases and emphasize the intricate interplay between geometry and frustration in kagome lattices.

InAs quantum wells (QWs) grown on InP substrates are interesting for their applications in devices with high spin-orbit coupling and their potential role in creating topologically nontrivial hybrid heterostructures. These QWs rely on InGaAs cladding layers and InAlAs barrier layers to confine electrons within a thin InAs well. The highest mobility QWs are limited by interfacial roughness scattering and alloy disorder scattering in the cladding and barrier layers. Increasing QW thickness has been shown to reduce the effect of both of these scattering mechanisms. However, for current state-of-the-art devices with As-based cladding and barrier layers, the critical thickness is limited to $\le 7$ nm. In this paper, we demonstrate the use of strain compensation techniques in the ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ cladding layers, grown on ${\mathrm{In}}_{0.81}{\mathrm{Al}}_{0.19}\mathrm{As}$ barrier layers, to extend the critical thickness well beyond this limit. We induce tensile strain in the InGaAs cladding layers by reducing the In concentration from ${\mathrm{In}}_{0.81}{\mathrm{Ga}}_{0.19}\mathrm{As}$ to ${\mathrm{In}}_{0.70}{\mathrm{Ga}}_{0.30}\mathrm{As}$ and we observe changes in both the critical thickness of the well and the maximum achievable mobility. The peak electron mobility at 2 K is $1.16\times {10}^6{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$, with a carrier density of $4.2\times {10}^{11}{\mathrm{cm}}^{-2}$. Additionally, we study the quantum lifetime and Rashba spin splitting in the highest mobility device as these parameters are critical to determine if these structures can be used in topologically nontrivial devices.

We assess the local symmetry and crystal environment of trivalent terbium ions embedded in an indium tin oxide matrix with bixbyite structure. The ${\mathrm{Tb}}^{3+}$ ions tend to substitute ${\mathrm{In}}^{3+}$ ions in two different cationic sites ($b$ and $d$). Density functional theory calculations suggest that the ${\mathrm{Tb}}^{3+}$ ions are mainly located at $C_2$ symmetry sites, relaxing selection rules and enabling electric dipole transitions, with the ${}^{5}D_4\to {}^{7}F_2$ transition being the most intense, providing a red color to the light emission. Photoluminescence emission spectrum under UV excitation at 83 K revealed 30 intra-$4f$ transitions, which were assigned to the ${}^{7}F_J$ ground multiplet of the ${\mathrm{Tb}}^{3+}$ ion. Crystal field analysis shows a strong alignment between calculated and observed energy levels, yielding a standard deviation of $\sigma =15.1{\mathrm{cm}}^{-1}$. We believe these results can help to understand the activation mechanisms of ${\mathrm{Tb}}^{3+}$ luminescent centers in transparent conductive oxides, as well as the potential to modulate ${\mathrm{Tb}}^{3+}$ emission color through its crystalline environment.

Computation has been extensively used to propose and investigate new strategies for arranging carbon on two-dimensional lattices. The goal is to find ways to modulate carbon's properties at the nanoscale to create new materials for broad applications. Graphene is the canonical 2D nanocarbon, but other structures with nonhexagonal rings feature attractive behaviors, including semiconducting properties, which are needed for the development of electronic devices at the nanoscale. Here, we propose a family of structures conceptually constructed from acepentalene-like building blocks. Unlike systems previously studied, the acepentalene units in these monolayers feature an asymmetric configuration. This structural specificity notably affects the electronic properties of the 2D lattices, which are semiconducting with a gap modulated by the linking hierarchy of the molecular units.

In geometrically frustrated magnetic systems, weak interactions or slight changes to the structure can tip the delicate balance of exchange interactions, sending the system into a different ground state. Brochantite, ${\mathrm{Cu}}_{\text{4}}{\mathrm{SO}}_{\text{4}}{\left(\mathrm{OH}\right)}_{\text{6}}$, has a copper sublattice composed of distorted triangles, making it a likely host for frustrated magnetism, but it exhibits stacking disorder. The lack of synthetic single crystals has limited research on the magnetism in brochantite to powders and natural mineral crystals. We grew crystals which we find to be a new polytype with a tendency toward ABAC stacking and some anion disorder, alongside the expected stacking disorder. Comparison to previous results on natural mineral specimens suggests that cation disorder is more deleterious to the magnetism than anion and stacking disorder. Our specific heat data suggest a double transition on cooling into the magnetically ordered state.