In this work, we develop a rapid reactive vapor transport technique to efficiently utilize limited isotopically pure precursors, particularly gaseous ${}^{18}\mathrm{O}_2$, and synthesize mm-scale, high-quality isotope-enriched crystals within few-minute growth durations. We unlock this capability by using metallic molybdenum precursors with high source temperatures ($900{}^{\circ }\mathrm{C}$) and total pressures ($\sim 1$ atm) to maximize precursor efficiency and yield. Subsequently, we grow $\alpha \text{−}\mathrm{Mo}{\mathrm{O}}_3$ single crystals with high and uniform enrichment levels of ${}^{98}\mathrm{Mo}$ and ${}^{18}\mathrm{O}$ isotopes in several different permutations. As probed by Raman spectroscopy, modest and significant phonon energy redshifts occur following ${}^{98}\mathrm{Mo}$ and ${}^{18}\mathrm{O}$ enrichment, respectively. By demonstrating control over both molybdenum and oxygen isotopic enrichments, we establish a powerful tool to advance nanophotonics and thermal management goals using $\alpha \text{−}\mathrm{Mo}{\mathrm{O}}_3$. This work is motivated by the possibility to enhance and engineer lattice vibrational mode phenomena including thermal conduction and hyperbolic phonon polariton dispersion—with particular interest in comparing the effects of light and heavy element enrichment.

The type-II Weyl semimetal ${\mathrm{WTe}}_2$ is a key material for exploring emergent quantum phenomena; therefore, there is intense demand for high-quality single crystals. Here, we report the successful growth of ultra-high-quality ${\mathrm{WTe}}_2$ single crystals using an improved Te flux method, achieving a world-record residual resistivity ratio (RRR) reaching $\sim 4000$, nearly doubling the previous record. These crystals exhibit an extremely large magnetoresistance of $\sim 1.3\times {10}^7\%$ and an average carrier mobility of $4.1\times {10}^5\mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ at 2 K and 9 T, both surpassing previous records. By systematically comparing crystals spanning a wide range of RRR values, we demonstrate that crystal quality strongly influences low-temperature quantum transport and Fermi surface (FS) properties in ${\mathrm{WTe}}_2$. The exceptional quality and size of our crystals enabled magnetic torque measurements and the first observation of de Haas-van Alphen (dHvA) quantum oscillations in ${\mathrm{WTe}}_2$. Furthermore, combining Shubnikov-de Haas and dHvA oscillations allows for a reliable three-dimensional mapping of the FS below 9 T. Through an angular-dependent analysis using both probes, we determine the complete set of FS parameters over the full angular range. The nearly constant and very small Dingle temperature $(1\sim 2 \mathrm{K})$ indicates long quantum lifetimes and weak, nearly isotropic scattering, highlighting the intrinsic electronic character of the ultra-high-quality ${\mathrm{WTe}}_2$ crystals. Our work demonstrates the critical role of crystal quality in unveiling the intrinsic electronic states of quantum materials and provides a general strategy for improving the quality of other telluride crystals, enabling further advances in quantum materials research.

A machine-learned interatomic potential (MLIP) for multilayer $\mathrm{Mo}{\mathrm{S}}_2$ was developed using the ultrafast force field (UF3) framework. The UF3 MLIP reproduces key properties in strong agreement with DFT including lattice constants, interlayer binding energies, and phase stability. Furthermore, the potential reasonably captures the phonon spectra and the highly anisotropic elastic tensor across monolayer (1H) and bulk (2H, 3R) $\mathrm{Mo}{\mathrm{S}}_2$ phases. Critically, defect and edge formation energies are captured with high fidelity, exhibiting a strong correlation with DFT (R² = 0.91) across ten defective monolayers and reproducing the difference between the free energies of zigzag and armchair edges within 5% of DFT. Nonequilibrium molecular-dynamics simulations reveal layered homoepitaxial growth consistent with experimental observations, demonstrating the formation of van der Waals gaps between successive epilayers and triangular domains bounded by zigzag edges. The robust UF3 MLIP, which is only approximately two times slower than the fastest empirical potentials, enables large-scale atomistic simulations of $\mathrm{Mo}{\mathrm{S}}_2$ epitaxial growth.

Hydrogen is an element frequently found within the lattice of the ${\mathrm{CuInSe}}_2$ (CIS) chalcopyrite and its alloys in solar-cell devices, in many occasions introduced intentionally to passivate the electrical activity of existing defect centers. The present study reports first-principles calculations of the formation energies of the intrinsic defects of the CIS compound and their interaction with hydrogen. This interaction was also studied by analyzing muon-spin spectroscopy observations that probed the evolution of the spin relaxation of this lighter hydrogenic isotope. The calculations covered an extended range of growth conditions and regions of the CIS phase diagram, through the elemental chemical potentials, leading to $p$-type and $n$-type material. From the final results, the most plausible trapping centers for monatomic hydrogen were identified through a self-consistent solution of the electroneutrality equation as a function of the growth conditions. The copper vacancies were found to be the defects with the higher concentration for $p$-type and $n$-type CIS, with the exception of copper-rich and maximally indium-poor conditions, where the Cu-to-In antisite strongly competes as the dominant acceptorlike defect. Defect association of hydrogen with both of these acceptor defects led to trapping with full and partial passivation, respectively, and binding energies of $\approx 0.6$ eV for the resulting defect complexes. The calculated energy landscape of the hydrogen interaction with the copper vacancy contains two energy minima, which control the local diffusion pathways and trapping energy of hydrogen at this defect. Calculations based on the nudged elastic-band method and transition-state theory led to the local trapping and detrapping energy barriers and associated dissociation temperature. The analysis of the muon-spin data showed clear evidence of muon trapping at native defects in the CIS lattice with the copper vacancy providing the best match of the calculated muon-spin relaxation with the experimental value.

In their 2023 article [Phys. Rev. Mater. 7, 075401 (2023)], Adhikari et al. predicted “excellent phase stability against decomposition” for all 12 ${\mathrm{Cs}}_{2}M\mathrm{Sb}{X}_6$ ($M=\mathrm{Cu}$, Ag, Na, K, Rb, Cs; $X=\mathrm{Cl}$, Br) halide double perovskites (HDPs). However, this optimistic claim relied on decomposition pathways limited to binary products, neglecting critical ternary competing phases. By rigorously incorporating all possible decomposition routes with experimentally validated structures, we demonstrate that only ${\mathrm{Cs}}_2{\mathrm{AgSbCl}}_6$ ($\mathrm{\Delta }{H}_{\mathrm{d}}=3.9$ meV/atom) and ${\mathrm{Cs}}_2{\mathrm{NaSbCl}}_6$ ($\mathrm{\Delta }{H}_{\mathrm{d}}=1.8$ meV/atom) are thermodynamically stable, while the remaining 10 HDPs are either marginally metastable (for ${\mathrm{Cs}}_2{\mathrm{AgSbBr}}_6, \mathrm{\Delta }{H}_{\mathrm{d}}=-2.6$ meV/atom) or intrinsically unstable. Notably, Cu(I)-based systems—such as ${\mathrm{Cs}}_2{\mathrm{CuSbCl}}_6$ and ${\mathrm{Cs}}_2{\mathrm{CuSbBr}}_6$ ($\mathrm{\Delta }{H}_{\mathrm{d}}=-37.6$ and −40.1 meV/atom)—exhibit severe instability due to Cu(I)'s inherent aversion to octahedral coordination, a key destabilizing mechanism previously overlooked. These results reconcile computational predictions with experimental synthesis feasibility, resolving long-standing discrepancies. This Comment underscores the necessity of modeling realistic competing phases and comprehensive decomposition thermodynamics in stability assessments of emerging multicomponent materials, challenging oversimplified approaches in materials design.

We respond to the Comment by Xiao et al. on our work [Phys. Rev. Mater. 7, 075401 (2023)], which questions the thermodynamic stability analysis of ${\mathrm{Cs}}_{2}M\text{Sb}X{}_6$ halide double perovskites. The Comment argues that the stability assessment is affected by the choice of decomposition pathways and by the structural models used for $\text{Cs}X$ compounds. Here we clarify that our original work evaluated thermodynamic stability through decomposition enthalpies with respect to experimentally motivated competing phases rather than formation energies relative to elemental references. We further discuss the role of alternative decomposition pathways, metastability, and experimental synthesis conditions in determining the realizability of halide double perovskites. We show that while the additional pathways considered in the Comment provide useful complementary insight, they do not invalidate the thermodynamic framework or the principal conclusions of our original study.

The search for novel nitride superconductors with superior mechanical properties is highly demanded for many potential applications, which, however, have been scarcely succeeded for the late $5d$ transition-metal nitrides, especially for the binary W-N compounds. Here we report the experimental identification of superconductivity in cubic $\mathit{cP}6\text{-WN}$ with the NbO-type structure by electrical transport, magnetization, and specific heat measurements, based on high-pressure synthesized samples. The superconducting properties of $\mathit{cP}6\text{-WN}$ are well determined and it belongs to a bulk type-II superconductor with a critical onset temperature of $T_{\mathrm{c}}=2.86\mathrm{K}$, showing weak electron-phonon coupling, short coherence length, and high upper critical field, likely due to its unique electronic and structural features. Pressure may slightly enhance electron-phonon interactions for gently promoting its $T_{\mathrm{c}}$ up to 3.83 K at 81 GPa, indicating the remarkable robustness of its superconductivity to external stress. This, combined with its exceptional mechanical hardness that rivals that of tungsten carbide (WC), makes it a compelling candidate for fabrication of durable superconducting electronics and coatings operating under high-stress conditions.

The development of advanced photonic devices requires precise control of the optical properties of semiconductors. Gallium phosphide (GaP) is a promising wide-band-gap semiconductor of fascinating nonlinear optical applications. Here, we present experimental evidence for the success in fine-tuning the optical band gap of GaP single crystals by irradiation with MeV–GeV heavy ions of a wide range of ion fluences. The large variety of ion parameters from different ion-beam facilities made it possible to distinguish between the effects caused by nuclear energy loss and electronic energy loss, demonstrating the ability of avoiding possible unwanted structural damage. The presented results are essential for the application of ion-beam technology in the fabrication of nanophotonic devices by providing unique active materials, exhibiting the potential of emitting light with various controlled wavelengths of high precision. Furthermore, our findings are of high necessity for monitoring and establishing precautions for radiation effects at aviation altitudes and in space systems.

Avalanchelike plastic bursts in crystalline materials follow power-law statistics, but the scaling exponents and cutoff parameters vary widely in the literature ($\alpha$ ranging from 1 to 2.2), hindering predictive modeling. Since distributions do not follow Gaussian behavior, the average of plastic kinetics is not correctly defined. Larger-scale models that rely on average behavior are therefore fundamentally flawed. We performed extensive three-dimensional dislocation dynamics simulations of fcc Cu deformation across three orders of magnitude in dislocation density ($\rho =5\times {10}^{10}\text{to}2\times {10}^{12}{\text{m}}^{-2}$) under constant strain rates. Our results demonstrate that the power-law exponent ($\alpha \approx 1.6\pm 0.1$) is invariant to both dislocation density and loading direction, resolving previous inconsistencies. However, dislocation density strongly controls the power-law truncation scaling ($\mathrm{\Delta }{\gamma }_{\max }\propto b/\sqrt{\rho }$) and the distribution of avalanche-triggering stresses. We quantify correlations between slip system activities and show how individual system contributions evolve with avalanche size. These findings reconcile experimental scatter in avalanche statistics and provide quantitative scaling laws for mesoscale-to-continuum plasticity models.

Local atomic and electronic structures of the ${\mathrm{YbB}}_{12}$(001) surfaces are studied by scanning tunneling microscopy and spectroscopy at low temperatures for revealing the hybridized surface electronic states. The surface was prepared by annealing in an ultrahigh vacuum at $1200{}^{\circ }\mathrm{C}$ for one hour. The annealing process preferentially removed the surface Yb atoms, and the surface exhibits a homogeneous $c(2\times 2$) structure. On the inhomogeneous surface prepared by $1400{}^{\circ }\mathrm{C}$ annealing for several seconds, there are three types of local $c(2\times 2$) structures. The local tunneling spectra at 5 K near the Fermi energy on the surfaces exhibit characteristic features consisting of a co-tunneling lineshape due to the Kondo lattice formation and an additional central peak. On the homogeneous surface, the shape of the central peak depends on the tip-surface distance, suggesting the $f-d$ hybridized nature of the surface electronic states.

The metallic oxide ${\mathrm{RuO}}_2$ hosts a fascinating edge case of magnetism: while nonmagnetic in ideal bulk material, density functional theory (DFT) predicts an altermagnetic ground state within the $\mathrm{DFT}+U$ method. The magnetic state of strained or doped thin films remains controversial, but evidence for a nontrivial magnetic state is ample. Here, I study the altermagnetic ground state of ${\mathrm{RuO}}_2$ on a higher rung of Jacob's ladder of density functional approximations, the meta-GGA level including the kinetic energy density and the density Laplacian. While the workhorse functional of solid-state physics is a generalized gradient approximation (GGA), the modern ${\mathrm{r}}^2\text{SCAN-L}$ functional has been established as a general-purpose functional which can replace GGA, while systematically improving solid-state properties without introducing spurious errors like erroneous magnetic ground states. Comparison of local spin-density approximation $\left(\mathrm{LSDA}\right)+U, \mathrm{GGA}+U$, and meta-$\mathrm{GGA}+U$ results on ${\mathrm{RuO}}_2$ shows systematic enhancement of the exchange interaction, leading to a reduction of the onset value of the Hubbard $U$ parameter at different levels of density functional approximation. However, the magnetic ground state, studied at the experimental lattice constants, remains nonmagnetic with ${\mathrm{r}}^2\text{SCAN-L}$. I demonstrate that altermagnetism is easily formed upon lattice expansion, hole doping, and uniaxial strain on the $c$ axis. The ${\mathrm{r}}^2\text{SCAN-L}$ calculations set conservative thresholds for distortions and doping levels for the onset of altermagnetism in a parameter-free framework.

Over the past two decades, various machine learning (ML) methods have been broadly used to predict properties from structure of materials, which is valuable in accelerating the discovery and development of new materials for different applications. Convolutional neural networks (CNN), however, have not been widely used in materials science, although they have been demonstrated to possess the state-of-the-art learning capability in the field of computer vision and pattern recognition. Recently, it was shown that CNN are powerful in predicting orientation-dependent properties when using a new structure representation—spatial density map (SDM). However, it is unclear whether the deep learning (DL) framework combining CNN and SDM is useful for predicting rotation-invariant properties because of the lack of rotational invariance of SDMs. Here, we demonstrate that this DL framework can also enable high-fidelity prediction of rotation-invariant properties through two examples, i.e., predicting the flexibility volume of metallic glasses and the grain-boundary segregation energy of polycrystals. This is realized through training CNN models via data augmentation and defining a common protocol to establish a unique local coordinate system to compute SDMs when applying CNN models. The advantages of the DL framework arise from the completeness of the SDM and the excellent learning capability of CNN models. Thanks to the high fidelity of CNN models, additional physical insights into structure–property relationships are obtained. The DL method is expected to be useful for a broad range of topics in materials science.

In ab initio studies of carrier-capture processes in defective semiconductor materials, the single-effective-mode formalism and the static-coupling approximation have become the predominant theoretical approaches for determining carrier-capture coefficients. The single-mode formalism relies on accurate nonequilibrium defect energies obtained from density-functional theory (DFT), where required inputs are a series of configurationally displaced, defect-containing supercells obtained using an interpolative ansatz, and where the DFT outputs are corresponding total energies that have traditionally been postprocessed using a long-established ground-state formulation of finite-size corrections and defect-formation energies. This formulation remains commonly used even though the defects that form a configuration-coordinate (CC) diagram typically exist as structures that are displaced from the ground state. To remedy this inconsistency, Kumagai has recently proposed novel methods for implementing finite-size corrections specifically intended for DFT calculations of the defect energies used to construct CC diagrams and implement the single-mode formalism [Y. Kumagai, Phys. Rev. B 107, L220101 (2023)]. Kumagai's approach builds on the latest finite-size-correction methods introduced to describe vertical charge-state transitions for charge-localizing point defects in semiconductors and insulators [T. Gake et al., Phys. Rev. B 101, 020102 (2020); S. Falletta et al., Phys. Rev. B 102, 041115 (2020)]. The newly identified finite-size artifact treated in these studies is the polarization charge induced on a configurationally frozen defect and its subsequent interaction with a vertical transition in charge state. In this work, we evaluate Kumagai's proposed methodology by applying it in a high-precision DFT study of carrier capture by substitutional ${\mathrm{C}}_{\mathrm{N}}$ in GaN, a well-characterized and technologically relevant defect and material. We have rigorously calculated ${\mathrm{C}}_{\mathrm{N}}$ defect energies across various supercell sizes for each defect configuration and charge state on the hole-capture CC diagram of ${\mathrm{C}}_{\mathrm{N}}$($q=-1$), enabling a direct comparison of the slopes of the defect energies versus inverse cell size with those predicted by Kumagai. The most consequential prediction of Kumagai's method is that these slopes distinctly vary as the square of the linear-interpolation parameter used to construct the nonequilibrium defect configurations. Our results quantitatively support this prediction. Moreover, with these new finite-size corrections and multiple-cell-size DFT calculations in place, we find that the classical energy barrier for hole capture by ${\mathrm{C}}_{\mathrm{N}}$($q=-1$) in GaN decreases to 0.092–0.127 eV. This finding confirms the recent ≈ 0.1 eV prediction of Reshchikov based on the weak temperature dependence for hole capture observed in photoluminescence experiments [M. A. Reshchikov, J. Appl. Phys. 129, 121101 (2021)]. These results stand in stark contrast to previously calculated barriers of 0.486 and 0.73 eV, which also used the single-mode formalism but were obtained by instead using ground-state-based finite-size corrections. Our reduced classical barrier for capture increases the temperature-dependent hole-capture coefficient of a ${\mathrm{C}}_{\mathrm{N}}$($q=-1$) defect by more than two to four orders of magnitude for temperatures of 100–600 K, compared to the previous 0.486 eV results. While other defects may not be as dramatically affected as here, we suggest that incorporating proper finite-size corrections for the vertical-transition-like states embedded within CC diagrams is an essential, yet previously unrecognized, component of accurate modeling of carrier-capture when using the single-effective-mode formalism.

We have investigated the vanadium-based Kagome metal ${\mathrm{YbV}}_3{\mathrm{Sb}}_4$ using density functional theory (DFT) combined with the Wannier function analysis. We explore the electronic properties, de Haas-van Alphen (dHvA) effect, and Fermi surface. Our calculations reveal the metallic characteristic in which the majority of the states around the Fermi energy ${\mathrm{E}}_F$ is contributed by the V-$3d$ orbitals, while the localized Yb-$4f$ states are positioned below it. The inclusion of spin-orbit coupling (SOC) induces the splitting of $\text{Yb-}4f$ states, while its impact on the $\text{V-}3d$ states is moderate. Furthermore, we have incorporated $\mathrm{U}+\mathrm{SOC}$, where the Hubbard parameter, which drastically changes the $\text{Yb-}4f$ states, creates additional splitting, leading to three distinct peaks in the density of states (DOS). Meanwhile, the $\text{V-}3d$ atoms with the Kagome lattice contribute the maximum to the transport properties, exhibit flat bands near the ${\mathrm{E}}_F$, while being protected under SOC and $\mathrm{U}+\mathrm{SOC}$. Herein, we report the vulnerability of the $\text{Yb-}4f$ states under SOC and $\mathrm{U}+\mathrm{SOC}$. Furthermore, the Fermi surface is found to comprise quasi-2D cylindrical sheets centered at the $\mathrm{\Gamma }$ point, along with smaller pockets near the Brillouin zone boundaries, which, under combined $\mathrm{U}+\mathrm{SOC}$, a small spherical pocket emerges, and the cylindrical sheet exhibits slight deformations. The dHvA frequencies reach as high as 70 kilotesla, which increases with tilt angle, exhibiting a nearly parabolic trend as expected for cylindrical orbits, while a low-frequency branch remains below 1 kilotesla. Only the $\mathrm{U}+\mathrm{SOC}$ case shows noticeable modification in both the Fermi surface and the dHvA oscillation. Crucially, the $Z_2$ invariant calculation identifies ${\mathrm{YbV}}_3{\mathrm{Sb}}_4$ as a strong topological metal (${\nu }_0=1$). These findings not only advance our understanding of the underlying quantum phenomena in rare-earth Kagome systems, but also establish ${\mathrm{YbV}}_3{\mathrm{Sb}}_4$ as a compelling and promising platform for exploring intertwined topology and electron correlations in Kagome lattices, thereby offering valuable insights for engineering quantum phases in layered materials.

We investigated the thickness dependences of the interfacial Dzyaloshinskii-Moriya interaction (DMI) and the perpendicular magnetic anisotropy (PMA) in ${\left(\mathrm{Pt}/\mathrm{Co}/\mathrm{W}\right)}_5$ multilayers by systematically varying the Co (from 1.3 to 1.9 nm) and W (from 0 to 3 nm) layer thicknesses. Vibrating sample magnetometer has been used to measure the magnetization at saturation from the Co-thickness dependence of the surface magnetic moment at saturation. Increasing the W spacer thickness induces an exponential decay of the magnetization, emphasizing the strong influence of the top interface on overall magnetic coupling. Both surface and volume PMA constants were quantitatively extracted from microstrip line ferromagnetic resonance (FMR) and Brillouin light scattering (BLS) as well as the magnetic damping and the interfacial DMI. A clear evidence of interfacial effects and magnetic inhomogeneities across the multilayers was provided by the appearance of two distinct resonance modes in the FMR spectra. By combining FMR and BLS, the origin of these modes, attributed to the different magnetic properties of the internal and the external Co magnetic layers in the multilayer, was confirmed. The criterion of skyrmions stability, applied for our samples, revealed the possibility of the existence of such stable chiral structures in some samples.