We present a diffuse neutron and x-ray scattering study of structural as well as spin- and charge-density-wave fluctuations in the electrical insulator $\mathrm{L}{\mathrm{a}}_{2-x}\mathrm{S}{\mathrm{r}}_x\mathrm{Ni}{\mathrm{O}}_4$. This lamellar nickelate is an isostructural analog of the high-temperature cuprate superconductor $\mathrm{L}{\mathrm{a}}_{2-x}\mathrm{S}{\mathrm{r}}_x\mathrm{Cu}{\mathrm{O}}_4$, for which recent experiments uncovered evidence for unusual structural and superconducting fluctuations indicative of rare-region physics due to inherent inhomogeneity unrelated to common point disorder effects. Here we find closely analogous nanoscale orthorhombic fluctuation behavior in $\mathrm{L}{\mathrm{a}}_{2-x}\mathrm{S}{\mathrm{r}}_x\mathrm{Ni}{\mathrm{O}}_4$, including exponential scaling of the diffuse scattering intensity and power-law scaling of the characteristic length with relative temperature. Moreover, our neutron and x-ray scattering data reveal similar behavior for short-range magnetic and charge fluctuations above the respective ordering temperatures. These observations indicate that rare-region effects are a generic feature of perovskite-related structures and lead to universal fluctuations of both structural and electronic degrees of freedom over extended temperature ranges.

The development of ZnO nanowires by the low-temperature, surface scalable, and easily implemented chemical bath deposition technique has been boosted for two decades by the great control over their structural morphology and properties with an excellent uniformity. However, the resulting ZnO nanowires suffer from relatively poor optical properties, which are highly detrimental for their efficient integration into real-world engineering devices. Here, we show that the hydrogen- and deuterium-plasma treatments result in a remarkable increase by more than two orders of magnitude in the intensity of the near‐band edge emission of ZnO nanowires through the formation of surface excitons, along with the large increase in the surface exciton lifetime from about 6 to 48 ps. The enhancement is attributed to an efficient passivation process of the surface defects of ZnO nanowires with hydrogen, further decreasing the density of surface traps from about $4.0\times {10}^{13}\mathrm{c}{\mathrm{m}}^{-2}$ to $3.8\times {10}^{12}\mathrm{c}{\mathrm{m}}^{-2}$, and it is also shown to be highly stable over time. These findings reveal that the structural and optical quality of ZnO nanowires grown by chemical bath deposition through the occurrence of surface excitons induced by hydrogen and deuterium passivation can approach those of much more sophisticated physical and chemical vapor deposition techniques proceeding at higher temperature and under vacuum. Eventually, the present plasma treatments offer a great opportunity to boost the optical quality of ZnO nanowires grown by chemical bath deposition for a vast number of optical and optoelectronics devices, renewing the high interest in the wet chemistry processes.

Soliton states of magnetostatic surface spin waves (MSSWs) hold great potential for nonlinear magnonics, yet their experimental existence remains elusive due to the difficulty in distinguishing them from other coherent states with phase modulations. Here, using phase- and spatiotemporal-resolved Brillouin light scattering spectroscopy, we resolve the phase evolution of MSSWs and identify two distinct nonlinear coherent phases: a dipole gap bright soliton under short-pulse excitation, evidenced by its characteristic phase plateau, and a coherent phase modulation under long-pulse excitation, exhibiting spatiotemporal periodicities—with nearly equal temporal periods in intensity and phase, and a spatial period in intensity linked to the temporal period via the group velocity. This coherent phase modulation originates from the four-magnon scattering, producing a tunable frequency-comb spectrum and displaying power-controlled nonreciprocity. Our work provides phase-resolved verification of MSSW solitons, reveals a coherent phase modulation, and establishes a multidimensional diagnostic framework for controlling nonlinear coherent phases in magnonics.

The dendritic microstructure that develops during solidification of metallic alloys plays a significant role in defining the characteristics of the material. The shape of dendrite tips directly influences the overall dendritic pattern, but in situ characterization of dendrite tips in bulk systems during directional solidification is rare because of experimental complexity. Here, we quantitatively characterize the three-dimensional (3D) tip shapes of dendrites grown during directional solidification of a transparent succinonitrile–0.46 wt% camphor alloy in the microgravity environment of the International Space Station, where convection is suppressed. The 3D reconstruction of the shape of dendrite tips is obtained through the analysis of interferometry images. Results are compared with both sharp-interface theory and 3D phase-field simulations. The experimental results are found to be in reasonably good quantitative agreement with the predictions of microscopic solvability theory and phase-field simulations despite a wider-than-expected scatter in measured tip radii that could be because of measurement uncertainties and other factors.

Building on earlier reports of superconductivity in bulk PtSb, we present a systematic study of superconductivity in epitaxial PtSb(0001) thin films grown on ${\text{SrF}}_2\left(111\right)$. Electrical transport measurements reveal a superconducting transition at $T_{\mathrm{c}}=1.72\mathrm{K}$. The field-induced broadening of the transition and the temperature dependence of the upper critical fields are consistent with type-II superconductivity. We determine the upper critical fields for magnetic fields applied perpendicular and parallel to the film plane and parametrize their temperature dependence using an anisotropic Ginzburg-Landau approach. For a representative film in the intermediate thickness regime ($d=50\mathrm{n}\mathrm{m}$), we obtain coherence lengths of ${\xi }_{ab}\approx 56\mathrm{n}\mathrm{m}$ and ${\xi }_c\approx 14\mathrm{n}\mathrm{m}$. Current-voltage characteristics show sizable critical currents, with a critical current density reaching $J_{\mathrm{c}}\approx 6\times {10}^4\mathrm{A}/{\text{cm}}^2$ at $0.5\mathrm{K}$. These results establish the superconducting properties of epitaxial PtSb thin films and provide a basis for lattice-matched heterostructures within the NiAs-type materials family.

Quantum sensing of meV-scale scattering and absorption of impinging particles with electrons in solid state detectors is a challenging technological advancement with the potential to enable breakthroughs in quantum information applications and studies of fundamental physics. However, a key obstacle for current sensing schemes is the difficulty in distinguishing the signals from particles of interest from false positive signals produced by intrinsic excitations, like phonons or magnons. Here, we propose a technique to selectively detect impinging particles based both on their imparted energy and also their imparted momentum to exploit the variability of dispersion relations amongst sources of meV-scale electronic excitations. By harnessing interfacial orbital hybridization in van der Waals heterostructures of Dirac materials, interlayer charge transfer may be promoted only for pre-selected impinging particles of interest. Using first-principles density functional theory (DFT) calculations of heterostructures of the layered Dirac materials ${\mathrm{ZrTe}}_5$ and ${\mathrm{HfTe}}_5$, we examine the effects of strain and layer number for successfully tuning orbital hybridization in their electronic structure. We demonstrate a proof-or-principle feasibility study for using Dirac materials to construct “dispersion filters” to be leveraged for next-generation meV-scale quantum sensors.

We have identified the optical signature of a variety of basal plane stacking faults (SFs) in AlN, exhibiting from one to five violations of the wurtzite stacking sequence. The unambiguous assignment of the emission energies to specific SFs was achieved by using a combination of scanning transmission electron microscopy and cathodoluminescence experiments performed on the same lamellae. Additional cathodoluminescence experiments have confirmed the spatially direct or indirect nature of the transitions and the role of polarization fields. Ab initio density functional theory (DFT) calculations for the different SF types were performed to determine their formation energies and electronic structures. SF luminescence energies were calculated using the one-dimensional envelope function approximation to solve the effective-mass Schrödinger equation. We find an excellent agreement between experiments and calculations. In particular, the DFT calculations reveal a crossover from momentum-direct to momentum-indirect recombination in the SFs, accounting for the higher emission energy of I3 relative to I2 SFs. This system provides an attractive platform for investigating spatially and momentum-indirect excitons.

Understanding the interplay between lattice dynamics and charge transport is essential for designing high-performance thermoelectric materials. In this work, we systematically investigate the thermoelectric transport properties of Zintl phase ${\mathrm{XInTe}}_2$ (X = Na, K, Rb) based on first-principles calculations. For lattice thermal transport, we apply self-consistent phonon theory (SCP) for the first time in this system and include the bubble diagram correction to accurately capture finite-temperature phonon renormalization. Moreover, the off-diagonal thermal conductivity contribution ${\kappa }_c$ is incorporated into the calculation of lattice thermal conductivity (${\kappa }_L$). Our results show that the enhanced Born effective charge (BEC) and large dielectric constant in ${\mathrm{NaInTe}}_2$ give rise to strong dynamic polarity, which enhances low-frequency phonon scattering through phonon branch softening and leads to a significant reduction in ${\kappa }_L$. In addition, nearly flat mid-frequency phonon branches are mainly associated with localized Na vibrations, exhibiting rattler-like behavior that further strengthens phonon scattering. For electronic transport, we use the amset framework to evaluate carrier transport properties by explicitly considering multiple scattering mechanisms, including grain boundary (MFP), acoustic deformation potential (ADP), ionized impurity (IMP), polar optical phonon (POP), and piezoelectric (PZ) scattering. As a result, p-type ${\mathrm{NaInTe}}_2$ exhibits a maximum $ZT$ of 2.54 at 800 K. When spin-orbit coupling (SOC) is included, the $ZT$ remains as high as 2.02, highlighting its robust thermoelectric performance.

We study the origin of interfacial shallow hole traps appearing in GaN-based metal oxide-semiconductor field-effect transistors (MOSFETs) using density-functional-theory calculations with realistic interfacial models. It is demonstrated that the ${\mathrm{GaO}}_x$ interfacial layer spontaneously formed at the ${\mathrm{GaN}/\mathrm{SiO}}_2$ interfaces, even without conventional point defects such as oxygen vacancies, induces hole traps. The holes are directly trapped at the tail state of amorphous ${\mathrm{GaO}}_x$, which are shown here to consist of $2p$ orbitals of low-coordinated O atoms with relatively high electrostatic potential. When occupied, these states are located just below the GaN valence band maximum, but upon hole localization, they are raised to the mid-gap region and become hole traps as a result of the lengthening of the Ga–O bonds.

Machine learning potentials (MLPs) have significantly advanced global crystal structure prediction by enabling efficient and accurate property evaluations. In this study, global structure searches are performed for 11 bismuth-based binary systems, including Na–Bi, Ca–Bi, and Eu–Bi, under pressures ranging from 0 to 20 GPa, employing polynomial MLPs developed specifically for these systems. The searches reveal numerous compounds not previously reported in the literature and identify all experimentally known compounds that are representable within the explored configurational space. These results highlight the robustness and reliability of the current MLP-based structure search. The study provides valuable insights into the discovery and design of novel bismuth-based materials under both ambient and high-pressure conditions.

${\mathrm{LiGa}}_5{\mathrm{O}}_8$ in a spinel-type structure has recently been claimed to be an unintentional $p$-type ultra-wide-band-gap oxide semiconductor. While previous computational work did not yet identify the origin of $p$-type doping and in fact predicted insulating behavior by compensation of deep acceptors by shallow donors, defect characterization in terms of its optical signatures remains important. Rather than focusing on thermodynamic transition levels, as in earlier work, this present paper focuses on the vertical transitions in a defect configuration diagram of defects in different charge states, representing absorption and emission processes involving carrier capture/emission from/to band edges. In addition, the structural relaxation of several native defects is revisited by allowing for more complex symmetry breaking distortions in an effort to reconcile conflicting results in the previous literature. Special attention is given to the Li vacancy because it is the shallowest native acceptor. For this defect, the previously reported transition levels are revised on the basis of symmetry breaking relaxations. The calculated optical transition energies are also compared with a representative depth-resolved cathodoluminescence spectrum of a mist-CVD-grown ${\mathrm{LiGa}}_5{\mathrm{O}}_8$ film. Finally, we also study carbon impurities, which may become relevant for identifying carbon-related defects in MOCVD-grown ${\mathrm{LiGa}}_5{\mathrm{O}}_8$ materials.

We present a comprehensive study on the sputtering behavior of tungsten fuzz structures under deuterium and argon ion bombardment using three-dimensional simulations. We employed SDTrimSP-3D to investigate porosity as a predictor for the sputtering behavior, complementary to the well-established effects of surface roughness, with simulations conducted across multiple ion energies ($500\mathrm{eV}–2000\mathrm{eV}$) and incidence angles ($0^{\circ }-{85}^{\circ }$). Fuzz structures were algorithmically generated with varying porosities, and sputter yields were systematically calculated. The findings reveal a universal linear relationship between sputter yield and porosity/volume filling, demonstrating that porosity significantly suppresses sputtering. Importantly, the zero-porosity limit is given by the sputter yield of a rough, but solid surface rather than a flat target. This linear behavior holds consistently across the different ion types and energies for a wide range of incidence angles. When normalized to the rough-surface sputter yield, the slope of the porosity dependence is nearly constant, indicating a common underlying suppression mechanism. The study enhances fundamental understanding of sputtering in porous nanostructures and provides a simple, predictive framework with implications for material design, particularly in nuclear fusion research, where erosion of tungsten fuzz impacts reactor component lifetimes.

Nonlinear optical phenomena induced by ultra-fast lasers in two-dimensional (2D) materials have recently attracted significant research interest. Herein, we investigate monolayer bismuthene using first-principles simulation based on the real-time Time-Dependent Density Functional Theory (rt-TDDFT). The results indicate that it exhibits a pronounced optical Kerr effect, with a negative nonlinear refractive index (NNRI) $n_2=-1.194\times {10}^{-9}{\mathrm{cm}}^2/\mathrm{W}$, whose absolute value is comparable to that of typical two-dimensional materials. By analyzing the electron transition probabilities among the conduction band minimum (CBM), valence band maximum (VBM), and $\mathrm{VBM}+1$, combined with perturbation theory for multi-level problems, we attribute the NNRI to the competition between two-level and three-level processes. This study clarifies the microscopic origin of NNRI in monolayer bismuthene, laying a theoretical foundation for unraveling the nonlinear optical regulation law of elemental two-dimensional bismuth-based nanomaterials.

The atomic structure of $\gamma$-alumina, a metastable oxide central to applications ranging from heterogeneous catalysis to energy conversion and environmental remediation, has remained elusive for decades. This persistent uncertainty arises from the high concentration of aluminum vacancies and the difficulty of determining precise cation occupancy within the oxygen sublattice. Here, we address this challenge by combining aberration-corrected scanning transmission electron microscopy combined with ultrahigh-sensitivity energy-dispersive spectroscopy to investigate $\gamma {\text{-Al}}_2{\text{O}}_3$ formed during high-temperature oxidation of NiAl alloys. By integrating atomic-resolution imaging, elemental mapping, diffraction analysis, and density functional theory calculations, we identify a spinel-type $\gamma {\text{-Al}}_2{\text{O}}_3$ structure featuring a cubic close-packed oxygen framework, in which Al cations exclusively occupy octahedral interstitial sites. This site-selective occupancy leads to ordered distribution of aluminum vacancies, resolving a long-standing structural ambiguity regarding cation distribution in $\gamma {\text{-Al}}_2{\text{O}}_3$. Comparison with previous studies of hydroxide-derived $\gamma {\text{-Al}}_2{\text{O}}_3$ further reveals that the local structure of this metastable oxide is highly sensitive to synthesis pathway, precursor chemistry, and kinetic equilibration history. These results provide direct atomic-level insight into defect ordering and cation topology in $\gamma {\text{-Al}}_2{\text{O}}_3$, with implications for ion transport, catalytic activity, and thermal stability in alumina-based materials.

We successfully synthesized $\left[\mathrm{Co}{\left(m\text{−}\mathrm{Py}\text{−}\mathrm{V}\right)}_3{\left({\mathrm{NO}}_3\right)}_2\right]$, in which a ${\mathrm{Co}}^{2+}$ ion adopts a seven-coordinate pentagonal bipyramidal (PBP) geometry. Molecular orbital calculations reveal that one of the three verdazyl radicals in the molecule forms a nonmagnetic singlet dimer through the strong intermolecular interaction, leading to a triangular spin necklace composed of the remaining spin-1/2 radicals and a spin-3/2 ${\mathrm{Co}}^{2+}$ ion. Magnetic susceptibility and specific heat measurements reveal contributions from ferromagnetic and antiferromagnetic exchange interactions, as well as a low-temperature phase transition. Electron spin resonance spectra and magnetization curves are consistently explained using a simplified model that treats the system as an anisotropic $S=3/2$ monomer coupled to an isotropic $s=1/2$ chain. Our results demonstrate that introducing PBP-coordinated transition-metal centers into radical-based complexes provides an effective route to incorporating strong magnetic anisotropy into designed quantum spin models, establishing a versatile platform for exploring frustrated and anisotropic triangular spin necklaces.

Molecular beam epitaxy (MBE) is renowned for its potential for atomic layer control, but unexpected growth mechanisms can potentially compromise this level of precision. In this study, we employ first-principles calculations to investigate the atomistic processes governing the MBE growth of perovskite ${\mathrm{SrTiO}}_3$ and Ruddlesden-Popper ${\mathrm{Sr}}_2{\mathrm{TiO}}_4$ films on a ${\mathrm{SrTiO}}_3$ substrate. We systematically explore the potential molecular species in the gas phase and their reactions and diffusion dynamics on the film surfaces and layer edges. Our analyses uncover three mechanisms of importance for understanding this type of growth. First, oxygen vacancies can be dynamically induced during surface diffusion on defect-free substrate and noticeably accelerate the diffusion processes. Second, while the SrO layer is expected to grow in a single-layer growth mode, the presence of potential ${\mathrm{Ti}}_{\mathrm{Sr}}$ defects may promote the formation of SrO islands. Lastly, adsorbed Ti atoms and ${\mathrm{TiO}}_2$ molecules on the SrO bilayer can insert into SrO bilayers, resulting in an unexpected growth sequence. These findings may have broader implications for the MBE growth of metal oxide films and provide guidance for achieving improved control over their growth processes.