We investigate spacer-mediated long-range Dzyaloshinskii-Moriya interaction (LR-DMI) in $\mathrm{Co}/\mathrm{Cu}\left(n\right)/\text{HM}$ multilayers $(\text{HM}=\text{Pt}, \mathrm{Pd}, \mathrm{Ir}, \mathrm{W}, \mathrm{Mo})$ using first-principles calculations and micromagnetic simulations. LR-DMI shows a pronounced nonmonotonic, oscillatory dependence on Cu thickness, demonstrating that the intralayer DMI within Co can be tuned through a nonmagnetic spacer and a remote heavy-metal (HM) spin-orbit source. Atomic layer decomposition reveals that the LR-DMI signal is carried predominantly by the Co planes, and the heavy-metal overlayer acts as the spin-orbit source whose influence is transmitted through the Cu spacer and weakens with increasing $n$. Thickness-dependent electronic structure and charge density difference analyses link the oscillatory LR-DMI to spacer-tuned Co-Pt coupling and interface to interface charge redistribution that becomes progressively localized at larger $n$. Extending to different heavy-metal overlayers, all systems retain the same thickness-driven oscillatory backbone, while the amplitude and phase depend strongly on the heavy-metal species, consistent with $d$ band filling and relativistic character. Micromagnetic simulations for Pt and Ir stacks demonstrate that these first-principles LR-DMI trends translate into distinct field tunable skyrmion diameters and hysteresis behavior. These results establish a Co/HM1/HM2-type route for engineering single-layer DMI through nonmagnetic spacer and spin-orbit layers.

Transition-metal doping enables the introduction of spin functionality into halide double perovskites, while simultaneously modifying optical properties. Here, we combine controlled single-crystal growth, optical characterization, comprehensive electron paramagnetic resonance (EPR) spectroscopy, and first-principles modeling to identify the microscopic nature of Fe-related centers in Fe-doped ${\mathrm{Cs}}_2{\mathrm{AgBiBr}}_6$. Single crystals with nominal $\mathrm{F}{\mathrm{e}}^{3+}$ concentrations up to 15% in the precursor stage were grown using a controlled-cooling method, yielding reproducible Fe incorporation up to 0.1% with respect to Bi, without secondary phases. Despite this low concentration, Fe doping introduces electronic states that influence optical absorption and photoluminescence. EPR measurements reveal an S = 5/2 $\mathrm{F}{\mathrm{e}}^{3+}$-related center whose anisotropy follows the cubic-to-tetragonal phase transition below 120 K. Angular-dependent EPR resolves two configurations of this nearly axial spin center, with principal axes rotated by 90° and aligned with the a/b plane of the tetragonal lattice. Density-functional calculations attribute these centers to impurity-vacancy complexes, most likely ${\mathrm{Fe}}_{\mathrm{Bi}}\text{−}{\mathrm{V}}_{\mathrm{Br}}$, that stabilize in a basal configuration of the low-temperature phase. This approach resolves vacancy-coupled defect orientations, narrowing possible models to $\mathrm{F}{\mathrm{e}}^{3+}$-vacancy complexes and establishing them as stable, orientation-sensitive spin probes of structural symmetry in halide double perovskites, while providing a microscopic basis for tuning their magnetic and optical responses.

In this work, we provide high-precision thermal characterizations of $\beta \text{-G}{\mathrm{a}}_2{\mathrm{O}}_3$ single crystals across six crystallographic orientations ([001], [010], [100], [012], $\left[\overline{2}01\right]$, and $\left[\overline{1}02\right]$) using time-domain thermoreflectance (TDTR). Our measurements reveal a pronounced anisotropic thermal conductivity. Beyond establishing the benchmark values for bulk conductivity, we report a significant frequency dependence in the measured thermal conductivity that is primarily governed by the $\mathrm{transducer}/\beta \text{-G}{\mathrm{a}}_2{\mathrm{O}}_3$ interface. By varying transducer configurations, we demonstrate that this frequency dependence in TDTR measurements is not an intrinsic bulk characteristic but is instead governed by the boundary conditions at the interface. These findings resolve long-standing discrepancies in reported $\beta \text{-G}{\mathrm{a}}_2{\mathrm{O}}_3$ thermal conductivity data, offering a clearer framework for the thermal design of ultrawide bandgap devices.

${\mathrm{NiZr}}_2$ is a member of the transition metal (Tr) zirconide ${Tr\mathrm{Zr}}_2$ superconductor family having a ${\mathrm{CuAl}}_2$-type tetragonal structure. In this study, we report on two different pressure-induced properties of ${\mathrm{NiZr}}_2$. The first one is pressure-enhanced superconductivity; the transition temperature $\left(T_{\mathrm{c}}\right)$ reaches 4.8 K at $P=64.9$ GPa, while the $T_{\mathrm{c}}$ of ${\mathrm{NiZr}}_2$ at ambient pressure is lower than 2 K. From the calculated density of states (DOS) at the Fermi energy, we suggest that the enhancement of $T_{\mathrm{c}}$ cannot be explained by the change in DOS. The Debye temperature estimated from the resistance analysis increases with pressure, which suggests the possible correlation with the enhancement of superconductivity, while the $T_{\mathrm{c}}$ under pressure calculated based on a conventional model suggests that the conventional pairing is not sufficient to explain the pressure-enhanced $T_{\mathrm{c}}$. The second property is pressure-induced uniaxial negative thermal expansion (NTE). We performed synchrotron x-ray diffraction (XRD) under pressure at variable temperatures. From the temperature-dependent XRD patterns and the Rietveld refinement results, we confirmed the emergence of NTE along the $c$-axis in ${\mathrm{NiZr}}_2$. Since the NTE is one of the new functionalities in ${Tr\mathrm{Zr}}_2$, the pressure-induced NTE will be one of the important parts for developing new NTE materials and understanding the mechanism of NTE in the family and related materials.

Zinc oxide (ZnO) is a prototypical wide-band-gap semiconductor whose $n$-type conductivity can be tailored through extrinsic donor doping. However, the roles of defect association, compensation, and dopant mobility remain incompletely understood. We investigate Cl- and F-related defects in ZnO using screened hybrid density-functional calculations, with emphasis on substitutional donors, defect complexes, vacancy-mediated migration, and self-consistent carrier statistics. Substitutional chlorine and fluorine on the oxygen site, ${\mathrm{Cl}}_{\mathrm{O}}$ and ${\mathrm{F}}_{\mathrm{O}}$, are predicted to be shallow donors, with (+/0) transition levels above the conduction-band minimum and low formation energies under O-poor conditions. Halogen-native-defect complexes can be thermodynamically bound and provide possible compensation or passivation channels, but their impact on the carrier concentration depends on their equilibrium abundance and charge-state distribution. Self-consistent charge-neutrality calculations show that both Cl and F substitutional donors can sustain $n$-type conditions under the freeze-in treatment considered here, with the charge balance dominated by ionized substitutional donors and free electrons. Large vacancy-mediated migration barriers further indicate that substitutional halogen donors are kinetically stable after incorporation. These results provide a microscopic description of the thermodynamic, electronic, and kinetic factors governing Cl and F doping in ZnO.

Discontinuous shear thickening (DST) in dense suspensions leads to flow instabilities that limit processing in a wide range of industrial and natural systems. Although high-power ultrasound has long been known to fluidize these materials, the physical origin of this effect remains unclear. Here, we investigate adhesive cornstarch suspensions, in which DST emerges from fragile load-bearing force networks embedded within heterogeneous density-wave structures. Using a rheo-ultrasound setup, where high-power ultrasound is superimposed onto a constant shear-rate flow, we demonstrate that ultrasound does not suppress shear thickening but continuously shifts the DST transition toward higher shear rates, thereby reducing the apparent viscosity. This shift is evidenced by the collapse of stress probability distributions measured at different ultrasound amplitudes onto master curves, revealing a renormalization of the shear thickening transition. We interpret these results within a separation-of-timescales framework. Because the acoustic oscillation period is much shorter than the characteristic timescale of suspension restructuring, the suspension structure can be considered quasistatic on the acoustic timescale, while ultrasound generates high-frequency oscillatory interstitial flows that perturb the local hydrodynamic stresses within the force-network structure. Guided by scaling analysis and estimates of the relevant physical stresses and timescales, we show that several microscopic mechanisms—including ultrasound-induced boundary slip, localized acoustic streaming, and pore-scale hydrodynamic fluctuations that destabilize force networks—are compatible with the observed experimental results. These findings provide a physical framework for understanding acoustic control of shear thickening in adhesive dense suspensions and establish ultrasound as a promising strategy for controlling discontinuous shear thickening and associated flow instabilities.

Pyrite-structure iron disulfide, in addition to being an important mineral, is also an $\sim 1$-eV-band-gap semiconductor with substantial application potential. In particular, pyrite's earth-abundant, nontoxic, low-cost constituents, combined with its high visible light absorption, high carrier mobility, good minority carrier diffusion length, and other attributes, have led to it being pursued as a photovoltaic absorber material. An effort in this direction from the 1980s was not particularly successful, however, with pyrite-based solar cells not exceeding $\sim 3\%$ power conversion efficiency. Subsequent to that effort, increased focus on sustainable energy technologies drove a substantial resurgence of interest in ${\mathrm{FeS}}_2$, more closely focused on the fundamental obstacles to high performance as a photovoltaic absorber. This second wave of effort took place over the last 15 years or so, quite strongly focused on high-quality ${\mathrm{FeS}}_2$ single crystals as model systems. This Research Update aims to summarize the knowledge and understanding gained through this recent effort, focusing specifically on the electronic (mostly transport) properties of single-crystal pyrite. Highlighted advances include comprehensive study of surface conduction in ${\mathrm{FeS}}_2$, greatly improved understanding of doping, and consequent deeper insight into fundamental behavior such as conduction mechanisms, the insulator-metal transition, and doping-induced magnetism. Through such advances, substantial insights into the origins of the underperformance of pyrite ${\mathrm{FeS}}_2$ as a photovoltaic material have been obtained, to the point that fresh strategies for redesigned solar (and other) devices mitigating these problems can now be formulated and tested.

Alloys based on the Cu-Ag-Co system are of significant technological and scientific interest due to the limited mutual solubility of all three elements, which leads to complex microstructural behavior. In this work, we present the new classical interatomic potential for this system that accurately reproduces basic thermodynamic and kinetic properties, achieving an accuracy comparable to that of modern machine learning interatomic models. The potential is formulated in a classical functional form, which provides high computational efficiency and makes it well-suited for large-scale molecular dynamics simulations. As an example of application, we investigate atomic diffusion and precipitation in Cu-Ag-Co alloys. The model reproduces key trends in both self- and impurity diffusion, including the inverse correlation between diffusivity and melting temperature and the strong suppression of Co diffusion in the considered metals.

Coherent crystalline interfaces form when a pair of joined crystals share lattice sites. Such interfaces are ubiquitous in materials, minerals, and compounds, with examples including grain boundaries in polycrystals and phase boundaries in multiphase systems. Existing methodologies such as the topological model [R. C. Pond, X. Ma, Y. W. Chai, and J. P. Hirth, Topological modelling of martensitic transformations, in Dislocations in Solids Vol. 13, edited by F. R. N. Nabarro and J. P. Hirth (Elsevier, Amsterdam, 2007),  Chap. 74, pp. 225–261] provide a framework for understanding the nature of coherency between two crystals and the line defect content within an interface. However, these methods only consider states of coherency achieved via affine transformations. Here we show that in some interfaces, local relaxations in the form of nonaffine transformations lead to the introduction of additional coincidence sites within the interface; we term this class of interfaces e-coherent. These nonaffine relaxations are topologically equivalent to inserting disconnection (or disclination) dipoles or loops into the interface. Unlike traditional interfacial line defects, the defects associated with e-coherency cannot have long-range stress fields, and their motion alters the state of coherency between the crystals. Given these unique properties, we differentiate them from other defects by referring to them as discohesions. Through atomistic simulations and transmission electron microscopy, we show that the energetics and kinetics of e-coherent interfaces are strongly affected by the discohesion content in the interface, leading to fundamentally different behavior compared with non-e-coherent interfaces. We demonstrate that e-coherency occurs in grain, twin, and phase boundaries and that a given interface can have multiple possible e-coherent states. These results suggest that e-coherency is likely to be pervasive in crystalline solids.

Machine-learning models in physical sciences often assume that complex emergent properties can be predicted using a single homogeneous inference task. However, many physical phenomena are intrinsically conditional, involving distinct processes governing phase feasibility and physical-property optimization. Here we show that superconductivity prediction is more naturally formulated as a hierarchical inference problem in which superconducting feasibility and critical-temperature $\left(T_{\mathrm{c}}\right)$ optimization are represented by a shared descriptor space with task-dependent reweighting. Using a balanced dataset of more than 26 000 inorganic materials comprising both superconductors and nonsuperconductors, we demonstrate that superconducting feasibility is primarily controlled by an electronic–compositional backbone, whereas achievable $T_{\mathrm{c}}$ depends on additional structural and magnetic/orbital effects. Guided by this decomposition, we construct a physics-aligned hierarchical learning framework that first predicts superconducting feasibility using the electronic–compositional backbone and subsequently predicts $T_{\mathrm{c}}$ using an expanded descriptor set. Feature clustering and Shapley additive explanation-based attribution further show that the electronic–compositional backbone provides a minimal dominant representation of feasibility, while additional descriptor groups modulate achievable $T_{\mathrm{c}}$ through constraint and context-dependent effects. The two-stage framework reduces end-to-end $T_{\mathrm{c}}$ prediction error by explicitly accounting for the conditional nature of superconductivity. These results establish superconductivity prediction as a hierarchically structured problem and provide a physically interpretable bridge between data-driven discovery and first-principles modeling, defining a sequential design principle for superconductor discovery. More broadly, the results show that physically interpretable machine-learning behavior can emerge from hierarchical organization and conditional reweighting within descriptor space rather than from increasingly complex model architectures.

Motivated by recent experimental breakthroughs in mixed-anion solid-state Li-ion electrolytes [Z. Liu et al., Nat. Chem. 16, 1584 (2024); F. Zhao et al., Science 390, 199 (2025)], we propose a previously unexplored mixed-halide rare-earth Na-ion solid electrolyte, ${\mathrm{Na}}_3{\mathrm{GdCl}}_4{\mathrm{Br}}_2$ (NGCB), and systematically establish its structure-transport-stability relationships using density functional theory, ab initio molecular dynamics, and grand-potential phase diagram analysis. Our computational simulations suggest that NGCB is stable dynamically, thermally, thermodynamically, and mechanically, with a wide electronic band gap of 5.73 eV and a broad electrochemical stability window of 0.57–3.65 V. Moreover, we reveal that anion mixing in NGCB generates tetrahedral anion vacancies that percolate into continuous low-barrier tetrahedral-tetrahedral $\mathrm{N}{\mathrm{a}}^{+}$ migration networks. Consequently, NGCB exhibits a high room-temperature ionic conductivity of 5.05 $\mathrm{mS}\mathrm{c}{\mathrm{m}}^{-1}$ with a low activation energy of 0.23 eV, supported by low migration barriers of 0.38–0.46 eV in two-dimensional channels and 0.40–0.45 eV in three-dimensional channels. Beyond fast ion transport, we show that anion mixing simultaneously enhances interfacial electrochemical compatibility. NGCB displays low interfacial reaction energies with high-voltage cathodes, reaching −32 $\mathrm{meV}\mathrm{ato}{\mathrm{m}}^{-1}$ with ${\mathrm{Na}}_3{\mathrm{V}}_2{\mathrm{P}}_2{\mathrm{O}}_8{\mathrm{F}}_3$. These results demonstrate a clear advantage of mixed-anion sodium solid-state electrolytes over conventional single-anion halides.

Despite extensive research on pearlite formation, the rate-controlling mechanisms of pearlite growth remain under debate. Phase field modeling has become a key tool for investigating such transformations; however, in solid-state systems where diffusion occurs both within individual phases and along their interfaces, the commonly assumed local-equilibrium boundary conditions are rarely satisfied, leading to artificial interface effects in conventional diagonal formulations. Here, we present a thermodynamically consistent nondiagonal three-phase field model formulated within the grand-potential framework to investigate pearlite growth. By introducing an Onsager-symmetric cross-coupling term between conserved and nonconserved order parameters, the model inherently recovers the correct equilibrium boundary conditions regardless of the active diffusion pathways, including bulk diffusion and interfacial diffusion. We systematically analyze four diffusion scenarios: (i) diffusion in austenite; (ii) diffusion in austenite, ferrite, and cementite; (iii) diffusion in austenite and ferrite; and (iv) diffusion in austenite combined with interfacial diffusion along austenite/ferrite and austenite/cementite boundaries. The model's quantitative performance is benchmarked against available analytical solutions for each case. Overall, the proposed framework provides a robust and thermodynamically sound approach for elucidating how different diffusion pathways control pearlite growth kinetics.

Functionalization of 2D materials and of transition metal dichalcogenides (TMDs) in particular is central for next generation devices and other applications. Here we study the effect of calcium dosing on the surfaces of clean ${\mathrm{WSe}}_2$ and ${\mathrm{WS}}_2$ in ultrahigh vacuum by x-ray photoelectron spectroscopy, low energy electron diffraction, and scanning electron microscopy. We find that Ca reacts with the chalcogens to ${\mathrm{CaSe}}_x$ or ${\mathrm{CaS}}_x$ and reduces the remaining tungsten. Ca forms an overlayer on top and causes an outdiffusion of the chalcogen. The overlayer oxidizes easily. We obtained detailed understanding of the interactions of archetypal TMD with an abundant alkali-earth element, which expands our knowledge of metal-surface interactions and of surface manipulation of 2D materials.

Two-dimensional pentagonal materials have recently emerged as a promising platform for exploring novel magnetic phenomena. Using first-principles calculations, we systematically investigate the strain-tunable optical and magnetic properties of $\mathrm{penta}\text{−}{\mathrm{FeS}}_2$ monolayer. Our results reveal that the system stabilizes into a distinct stripy-AFM ground state under ambient conditions. This ordering is driven by strong magnetic frustration originating from the dominant third-nearest-neighbor antiferromagnetic exchange interaction $\left(\right|J_3|\gg |J_1\left|\right)$. Furthermore, biaxial strain serves as a robust knob to tune these properties. Tensile strain induces a semiconductor-metal transition, where the emergence of itinerant electrons creates a screening effect that weakens the long-range exchange interaction, triggering a phase transition from stripy-AFM to Néel-AFM. In contrast, compressive strain preserves the semiconducting gap while enhancing the interorbital hybridization. Additionally, tensile strain promotes a spin reorientation transition from in-plane to out-of-plane. Our work demonstrates the microscopic interplay among lattice geometry, electronic screening, and magnetism in $\mathrm{penta}\text{−}{\mathrm{FeS}}_2$, positioning it as a versatile candidate for magneto-optoelectronic applications.

We investigated the electronic properties of $RE{\mathrm{Ru}}_6{\mathrm{As}}_4(RE=\mathrm{La}, \mathrm{Ce}, \mathrm{Sm}, \text{and} \mathrm{Yb})$ using single-crystalline samples grown by the Bi-flux method. These compounds crystallize in the noncentrosymmetric hexagonal ${\mathrm{LiCo}}_6{\mathrm{P}}_4$-type structure, featuring chain-like and triangular arrangements of magnetic $RE$ ions. From the electrical resistivity, magnetic susceptibility, and specific heat measurements, we have found that ${\mathrm{SmRu}}_6{\mathrm{As}}_4$ and ${\mathrm{YbRu}}_6{\mathrm{As}}_4$ order antiferromagnetically below the Néel temperature of 1.5 and 9.5 K, respectively. Despite the relatively high transition temperature of ${\mathrm{YbRu}}_6{\mathrm{As}}_4$, its magnetic field-temperature phase diagram reveals that the antiferromagnetic state collapses at a low field of ${\mu }_0{H}_{\mathrm{c}}=1.7\mathrm{T}$, accompanied by an unusual nonlinear magnetization. The small critical field and characteristic magnetization curve in ${\mathrm{YbRu}}_6{\mathrm{As}}_4$ suggest an important role of competing interactions associated with magnetic frustration.

This study employed first-principles calculations to investigate the thermoelectric transport properties of the KXSb $(X=\mathrm{Ge},\mathrm{Sn},\mathrm{Pb})$ series compounds. Both the harmonic approximation (HA) and self-consistent phonon (SCP) theory were adopted, incorporating multiple phonon scattering mechanisms and spin-orbit coupling (SOC) effects. The results reveal that the chemical bonding characteristics and mechanical properties evolve systematically with increasing atomic number of X. The KXSb series exhibits pronounced lattice anharmonicity. As the atomic mass increases, the phonon spectrum progressively flattens, which, through multiple mechanisms, leads to ultralow lattice thermal conductivity. Three-phonon scattering is identified as the dominant mechanism suppressing lattice thermal conductivity, while four-phonon scattering provides an important additional contribution. In terms of electronic transport, SOC induces significant spin splitting in the band structure, substantially affecting the thermoelectric quality factor. An anomalous sign reversal of the Seebeck coefficient is observed in electrical transport, which originates from the bipolar transport effect associated with the narrow band gap and band anisotropy. Furthermore, the electrical transport performance under $n$-type doping is generally superior to that under $p$-type doping. As a consequence of these combined effects, the KXSb series exhibits excellent thermoelectric performance, with KSnSb achieving a maximum ZT of approximately 3.77 at 800 K.

The ability to minimize low-temperature acoustic loss in amorphous materials would have implications in fields as wide-ranging as gravitational wave detection and quantum computing. In this paper, we measure the internal friction between $300\mathrm{mK}$ and room temperature of several thin silica films deposited by ion beam sputtering onto ultra-high-$Q$ silicon resonators. The measurements reveal internal configurations of as-deposited films that are markedly different from that of bulk silica. Over a broad temperature range, the films' internal frictions differ from one another by a factor of two; by contrast, a review shows that sub-MHz internal friction measurements of bulk silica fall within a 35% band with a pronounced main absorption peak between $20\mathrm{K}$ and $40\mathrm{K}$. This peak is absent in the films presented here, except for one film that had been annealed at $900{}^{\circ }\mathrm{C}$. Annealing at $500{}^{\circ }\mathrm{C}$ erased the thermal histories of the other thin films to create internal friction values that are consistent from film-to-film but yet still markedly different from those of the bulk below $100\mathrm{K}$, while creating the steep bulk-like drop-off above $100\mathrm{K}$ that the as-deposited films lacked. In the context of theoretical structural modeling, our results suggest that exposure to temperatures of at least $900{}^{\circ }\mathrm{C}$ is needed to form the network of tetrahedra considered characteristic of amorphous silica. The present measurements, especially when compared alongside previous work, appear to show that these structures are suppressed in many thin film preparations. These measurements also show, for as-deposited films, an excess of excitations in the 0.15–$0.3\mathrm{eV}$ range which can be annealed away to bring about the $Q^{-1}$ drop-off above the main absorption peak. The shear moduli of all the films are qualitatively similar to bulk silica, with a positive temperature coefficient above a minimum near $60\mathrm{K}$ and a negative temperature coefficient below.