We present a machine learning (ML) guided approach to predict saturation magnetization $\left(M_{\mathrm{S}}\right)$ and coercivity $\left(H_{\mathrm{C}}\right)$ in Fe-rich soft magnetic alloys, particularly Fe-Si-B systems. ML models trained on experimental data reveal that increasing Si and B content reduces $M_{\mathrm{S}}$ from 1.81 T $(\mathrm{DFT}\approx 2.04 \mathrm{T})$ to $\approx 1.54$ T $(\mathrm{DFT}\approx 1.56\mathrm{T})$ in Fe-Si-B, which is attributed to decreased magnetic density and structural modifications. Experimental validation of ML predicted magnetic saturation on Fe-1Si-1B (2.09 T), Fe-5Si-5B (2.01 T), and Fe-10Si-10B (1.54 T) alloy compositions further supports our findings. These trends are consistent with density functional theory predictions, which link increased electronic disorder and band broadening to lower $M_{\mathrm{S}}$ values. Experimental validation on selected alloys confirms the predictive accuracy of the ML model, with good agreement across compositions. Beyond predictive accuracy, detailed uncertainty quantification and model interpretability including through feature importance and partial dependence analysis reveal that $M_{\mathrm{S}}$ is governed by a nonlinear interplay between Fe content and early transition metal ratios, while $H_{\mathrm{C}}$ is more sensitive to processing conditions such as ribbon thickness and thermal treatment windows. The ML framework was further applied to Fe-Si-B/Cr/Cu/Zr/Nb alloys in a pseudoquaternary compositional space, which shows comparable magnetic properties to NANOMET $\left({\mathrm{Fe}}_{84.8}{\mathrm{Si}}_{0.5}{\mathrm{B}}_{9.4}{\mathrm{Cu}}_{0.8}{\mathrm{P}}_{3.5}{\mathrm{C}}_1\right)$, FINEMET $\left({\mathrm{Fe}}_{73.5}{\mathrm{Si}}_{13.5}{\mathrm{B}}_9{\mathrm{Cu}}_1{\mathrm{Nb}}_3\right)$, NANOPERM $\left({\mathrm{Fe}}_{88}{\mathrm{Zr}}_7{\mathrm{B}}_4{\mathrm{Cu}}_1\right)$, and HITPERM $({\mathrm{Fe}}_{44}{\mathrm{Co}}_{44}{\mathrm{Zr}}_7{\mathrm{B}}_4{\mathrm{Cu}}_1$. Our findings demonstrate the potential of the ML framework for accelerated search of high-performance soft magnetic materials.

Vertically stacked van der Waals structures are promising platforms that enable layer engineering, opening new avenues for the quantum control of elementary excitations, including optically generated bound electron-hole pairs. Here we employ excited-state density functional calculations to demonstrate strong interlayer excitonic coupling in one-dimensional van der Waals nanostructures derived from armchair graphene nanoribbons. The excitonic response exhibits prominent peaks in the near-infrared range, mainly attributed to intralayer excitons, while interlayer excitations with absorption peak strengths of up to 13% of the maximum absorption are also observed. Both type-I and type-II band alignments are found, which promote the formation of intralayer and interlayer excitons. Notably, interlayer excitons in these systems exhibit long-lived radiative lifetimes at room temperature, ranging from 1 ns to 9.4 µs. Our calculations suggest the potential to tune the excitonic response and lifetimes of bilayer graphene nanoribbons via careful engineering of the stacking order.

The formation of ω phase severely impairs the mechanical properties of metastable β-Ti and β-Zr alloys, causing embrittlement and loss of ductility, yet its transformation kinetics remain poorly understood. Using molecular dynamics simulations, we examine how chemical ordering influences the β→ω phase transformation in Zr-Nb alloys. Our results reveal that the nucleation of the ω-phase is influenced not only by the concentration of alloying elements, but also by the degree of chemical ordering along ${\langle 111\rangle }_{\beta }$ directions, with Nb atoms occupying two out of every three ${\left\{111\right\}}_{\beta }$ planes. Notably, in rapidly quenched Zr-10%Nb alloys, enhanced local chemical ordering leads to larger ω precipitates with their crystallographic orientation directed by the ${\langle 111\rangle }_{\beta }$ ordering of Nb atoms. This interaction results in nanosized, morphologically distinct athermal ω phases, facilitated by local ${\langle 111\rangle }_{\beta }$ ordering. The propensity for ω-phase formation in chemically ordered regions arises from a reduced shear modulus and lower transformation barriers. These insights provide valuable guidance for understanding microstructural control in developing high-performance titanium and zirconium alloys.

Yttrium iron garnet $(\mathrm{YIG}, {\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12})$ is a leading ferrimagnetic oxide for spintronic and magnonic applications due to its low magnetic damping and efficient spin transport via magnons. We investigate in-plane angular-dependent magnetic properties and interfacial effects in 104-nm-thick YIG films grown on gadolinium gallium garnet (GGG, ${\mathrm{Gd}}_3{\mathrm{Ga}}_5{\mathrm{O}}_{12}$) substrates using vibrating sample magnetometry (VSM), AC susceptibility, and ferromagnetic resonance (FMR) from 2 K to 300 K. FMR measurements (1–15 GHz) reveal a nonmonotonic temperature dependence of the resonance field $\left(H_{\mathrm{res}}\right)$, which decreases near 50 K and increases at lower temperatures. This behavior, along with clear magnetic phase changes near 20 K observed in VSM/AC magnetic susceptability (ACMS) data, is attributed to enhanced interfacial spin dynamics driven by the increasing paramagnetism of GGG at low temperatures. The damping constant $\left(\alpha \right)$ exhibits strong in-plane angular dependence $(\alpha \approx {10}^{-3}\text{–}{10}^{-2})$ below 50 K, indicating sensitivity to interfacial coupling and local defects. Our findings highlight the critical role of substrate-induced interfacial effects and magnetic anisotropy in determining YIG's low-temperature magnetic behavior, with important implications for future spintronic device design.

The density waves that develop in kagome metals ${\mathrm{ScV}}_6{\mathrm{Sn}}_6$ and ${\mathrm{LuNb}}_6{\mathrm{Sn}}_6$ at low temperature appear to arise from underfilled atomic columns within a V-Sn or Nb-Sn scaffolding. Compressing this network with applied pressure in ${\mathrm{ScV}}_6{\mathrm{Sn}}_6$ suppressed the structural transition temperature by constraining atomic rattling and inhibiting the shifts that define the structural modulation. We predicted that the density wave transition in ${\mathrm{LuNb}}_6{\mathrm{Sn}}_6$ at 68 K would be suppressed by pressure as well. In this Letter, we examine the pressure dependence of the density wave transition by measuring resistance vs temperature up to 2.26 GPa. We found the transition temperature is smoothly depressed and disappears around 1.9 GPa. This result not only addresses our prediction, but strengthens the rattling chains origin of structural instabilities in the ${\mathrm{HfFe}}_6{\mathrm{Ge}}_6$-type kagome metals.

${\mathrm{Ta}}_3\mathrm{Sb}$ is one of the A15 compounds that have been predicted to have giant spin Hall conductivities due to the gapped Dirac-like band crossings in their electronic structures. We use co-sputtering to directly synthesize thin films of ${\mathrm{Ta}}_3\mathrm{Sb}$ and identify a large window of Ta:Sb flux ratio that permits the formation of single-phase A15 structure. These sputtered films have an actual Ta:Sb atomic ratio of 4:1, as determined from Rutherford backscattering spectrometry. Their high resistivity, at the Mott-Ioffe-Regel limit, suggests that the electron mean free path is comparable to interatomic distances. From harmonic Hall and spin-torque ferromagnetic resonance measurements, the intrinsic spin Hall conductivity of thin film ${\mathrm{Ta}}_3\mathrm{Sb}$ is estimated to be in the range of $-526$ to $-1230\left(\hslash /e\right)\text{S/cm}$ at 300 K, lower in magnitude than the predicted value of $-1400\left(\hslash /e\right)\text{S/cm}$. First-principles calculations of the electronic structure show that the discrepancy is consistent with an increase of the Fermi level due to the nonideal stoichiometry needed to stabilize the A15 structure.

High-entropy alloys (HEAs) exhibit various physical properties, such as high microhardness for structured materials and high efficiency for catalysis. These features are recognized as a cocktail effect of five or more elements that stabilize a single-phase solid solution due to a high configurational entropy. HEAs may also exhibit short-range orders and microdistortions, which cause the local symmetry breaking of systems. Systems with local symmetry breaking are of interest for spin-dependent transport, such as for spin Hall effects. In this study, sputtered-film samples of an HEA, Mn-Nb-Mo-Ta-W, and related alloys, were fabricated; these films were layered with ferromagnetic CoFeB. All samples exhibited x-ray diffraction peaks originating only from a body-centered-cubic (bcc) phase, and transmission electron microscopy images indicated the absence of secondary phases and uniform elemental distributions. The spin Hall magnetoresistance (SMR) was investigated, and clear resistance changes were observed in all the samples. Quantitative analysis of SMR revealed that the spin Hall angle (${\theta }_{\mathrm{SH}}$) was $0.12\pm 0.002$ and $0.14\pm 0.037$ for the HEA and Nb-Mo-Ta-W alloy [medium-entropy alloy (MEA)], respectively. The ${\theta }_{\mathrm{SH}}$'s of the HEA and MEA were comparable to that of Pt which is a typical heavy element with relatively large ${\theta }_{\mathrm{SH}}$. The recently developed HEA and MEA films are attractive spin Hall materials with the bcc phase and are suitable for spintronic applications using magnetic tunnel junctions with CoFeB and an MgO barrier.

The combination of nontrivial topology and superconductivity opens to novel quantum devices. The discovery of intrinsic materials where such properties appear together represents a frontier in modern condensed matter physics. Trigonal ${\mathrm{PtBi}}_2$ has recently emerged as a possible candidate, being the first example of superconducting type I Weyl semimetal. However, several aspects of this promising compound still need to be unveiled, concerning its complicated band structure, the actual role of Weyl points in determining its electronic properties and the nature of the superconducting transition. In this work, we experimentally investigated a $\mathrm{t}\text{−}{\mathrm{PtBi}}_2$ single crystal by means of the Hall and Nernst effects. In particular, we revealed a change of regime in its electronic properties, which is compatible with a temperature and magnetic field evolution of holelike pockets in the Fermi surface.

Grain boundaries (GB) are effective defect sinks and can be engineered to enhance radiation tolerance in materials. The capacity of a GB to absorb radiation damage is influenced by the material's ability to accommodate new atoms into its internal structure. This work provides a quantitative link between material composition and self-interstitial atom (SIA) absorption efficiency through GB structural rearrangements. Molecular dynamics simulations are employed to reveal GB evolution to denser structural units in a chemically complex alloy, whereas the GBs in a pure material and dilute alloy establish a steady structural state during the SIA deposition. Following, regions of structural transformation are correlated to large positive misfit volume differences and thus higher hydrostatic stress. This environment drives GB structural unit transformations to relieve stress and accommodate the absorbed defects. There is an additional driving force from chemistry which promotes structural transformations given nominally lower values of local stress. These regions are mostly rich in Co and Cr, which are also the regions where we observe more pronounced SIA absorption events. Energetically, we find that it is this balance of thermodynamics and mechanical stress which stabilizes specific GB structures. GBs in pure Ni, $\mathrm{N}{\mathrm{i}}_{95}\mathrm{C}{\mathrm{r}}_5$, and equiatomic CoCrNi are evaluated as a function of SIA deposition into the GB. We find that chemistry has an unequivocal role in widening the available microstate range for defect absorption, which highlights chemical tailoring as a pathway for enhanced radiation resistance due to elevated GB absorption efficiencies.

${\mathrm{HfO}}_2$-based ferroelectric films have demonstrated great potential in nonvolatile memory, sensors, and energy harvesting applications. Although the ferroelectricity of ${\mathrm{HfO}}_2$ thin films can persist at the nanoscale, depolarization effects often lead to polarization degradation or even complete suppression. The underlying physical mechanisms governing this phenomenon remain controversial. Here, the depolarization mechanism of ${\mathrm{HfO}}_2$ films was thoroughly explored based on first-principles calculations, and results reveal that surface phase transitions play a vital role in the depolarization process. Although ferroelectric bulk phases for both $\mathrm{Pca}{2}_1$ and $\mathrm{Pmn}{2}_1$ are stable, out-of-plane ferroelectric (010) $\mathrm{Pca}{2}_1$ film is thermodynamically unstable and transforms into $\mathrm{P}{2}_1/\mathrm{c}$ spontaneously via an effectively barrierless twisting pathway. Notably, only out-of-plane electric polarization is reduced, while the in-plane one remains. Moreover, the tensile strain induced in ${\mathrm{HfO}}_2$ films by realistic substrates such as ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_{\mathrm{x}}{\mathrm{MnO}}_3$ (x ≈ 0.2 ∼ 0.4) induces a transformation of the film from the paraelectric $\mathrm{P}{2}_1/\mathrm{c}$ phase to the antiferroelectric Pbcn one. Subsequently, during the wake-up process, the Pbcn phase can transition into the ferroelectric phase through a low-energy barrier. This study offers insights into the depolarization mechanisms in ${\mathrm{HfO}}_2$-based ferroelectrics and presents strategies for optimizing interfacial properties and tuning phase structures, thereby providing valuable theoretical guidance for enhancing phase stability in hafnium-based ferroelectric thin films.

The magnetic compensation effect in rare-earth/transition metal alloys, in which the magnetization of the antiferromagnetically aligned rare-earth and transition metal sublattices cancel each other out, can be utilized in a number of novel applications. However, nanoscale composition variations of the rare-earth/transition metal ratio broaden the temperature range of magnetic compensation (i.e., near zero net magnetization) and can even result in the reversal of the dominant magnetic sublattice at a given temperature. We observe a spin reorientation in sputter-grown $\mathrm{F}{\mathrm{e}}_{1-x}\mathrm{G}{\mathrm{d}}_x$ thin films with nominal $x=0.28$ as a function of film thickness. Thicker films (> 50 nm thickness) exhibit an in-plane anisotropy near room temperature, while robust out-of-plane anisotropy is observed in thin films ($\sim 16$ nm) at all temperatures. Correspondingly, the compensation temperature for thick films is near 25 K, while that for thin films is above room temperature. A film with intermediate thickness ($\sim 35$ nm) displays a more complicated evolution of magnetic configurations. X-ray and polarized neutron scattering indicate that while structurally the intermediate thickness film appears homogeneous along the film normal direction, its depth-dependent magnetization profile is unusual, with two phases that have different compensation behavior. Elemental mapping using high-resolution electron microscopy reveals column formation leading to lateral variations in the Fe:Gd ratio near the top of the film, while Fe and Gd are uniformly distributed near the bottom of the layer. Our results identify an unexpected transitional thickness region in $\mathrm{F}{\mathrm{e}}_{1-x}\mathrm{G}{\mathrm{d}}_x$ films where the nonuniform elemental distribution leads to complex multistep magnetization behavior that should be controlled or could be leveraged in spintronic and magneto-optical applications.

Understanding the deformation of materials at the nanoscale level provides insights into the incipient deformation process. Additionally, comprehending how a material deforms directly improves understanding of its mechanical properties. For atomic crystals such as metals and ceramics, direct observation of nanoscale deformation has clarified how materials deform and fracture while revealing the key factors governing the deformation process. However, in systems where the constituent elements themselves are significantly larger, understanding the deformation process is important not only for theoretical framework development but also for gaining new insights into deformation mechanisms. In this study, we investigated the deformation mechanisms of macromolecular crystals using protein crystals as a model, which consist of significantly larger molecular components than conventional atomic or small-molecule crystals. Through microscale indentation observation via x-ray topography, we revealed that plastic deformation occurs via the nucleation and motion of dislocations, which can be explained by the conventional dislocation theory. Nanoindentation experiments at a scale smaller than the molecular size of macromolecular crystals, along with estimations of the activation volume of dislocations, demonstrated that the molecules deform slightly at the incipient stage before dislocation nucleation. This finding indicates that the size of the constituents in materials affects material deformation, and it suggests the potential for expanding deformation mechanisms by considering the characteristics of the constituent components.

Single crystals of natural rhodochrosite show a large phonon-driven thermal expansivity along the trigonal $c$ axis $({\alpha }_{\parallel }=\frac{1}{c}{\left(\frac{\partial c}{\partial T}\right)}_p=1.53\times {10}^{-5}{\text{K}}^{-1}\text{at}T=120\text{K})$ and a negligible expansivity perpendicular to it $({\alpha }_{\perp }=\frac{1}{a}{\left(\frac{\partial a}{\partial T}\right)}_p=0.057\times {10}^{-5}{\text{K}}^{-1}\text{at}T=120\text{K})$. Impurities in minor concentrations, particularly calcium, seem to be responsible for this one-dimensional thermal expansivity. Interestingly, at lower temperatures ($T\lesssim$ 50 K) where the magnetic interactions switch on, ${\alpha }_{\perp }$ awakens and gives rise to an anisotropic three-dimensional magnetic thermal expansivity, most probably associated with a prominent isotropic magnetoelastic coupling. This is confirmed by magnetostriction experiments. Our results show that expansivity can be easily fine-tuned (from positive to negative) by small amounts of impurities naturally present in carbonate minerals, in contrast with much more sophisticated methods used in functional materials.

$M_3{A}_{2}X$ phase is a type of ternary layered MAX-phase-like materials. To date, only four stable $M_3{A}_{2}X$ phases have been discovered. In this research, high-throughput density functional theory calculations were employed to systematically identify stable $M_3{A}_{2}X$ phases and then predict their properties. Starting from 240 possible compositions and 51 structural models for each composition, 12 $M_3{A}_{2}X$ phases successfully passed three rounds of stability assessment (thermodynamic, dynamic, and mechanical stabilities) and thus are stable. Crystal structures of stable ${\mathrm{Sc}}_3{\mathrm{S}}_2\mathrm{C}, {\mathrm{Y}}_3{\mathrm{S}}_2\mathrm{C}$ and ${\mathrm{Y}}_3{\mathrm{Se}}_2\mathrm{C}$ are novel and different from those of synthesized $M_3{A}_{2}X$ phases. The electrical conductivities of the 12 $M_3{A}_{2}X$ phases are generally superior to those of corresponding classic $M_{2}AX$ phases, while their mechanical properties are slightly inferior. Through the comparison of bond strengths using the crystal orbital Hamilton population analysis, it has been discovered that $M_3{A}_{2}X$ phases have a greater tendency to exfoliate into 2D MXenes than $M_{2}AX$ phases. Among them, the ${\mathrm{Zr}}_3{\mathrm{Se}}_2\mathrm{C}, {\mathrm{Zr}}_3{\mathrm{S}}_2\mathrm{C}$, and ${\mathrm{Sc}}_3{\mathrm{S}}_2\mathrm{C}$ phases exhibit the highest exfoliation potential. This study provides a comprehensive understanding of $M_3{A}_{2}X$ phases, laying a solid foundation for future experimental synthesis and technological applications.

Yb-based triangular lattice materials have attracted significant attention due to their potential for hosting exotic magnetic quantum states. In this paper, we report the structural, magnetic, and thermodynamic properties of two Yb triangular lattice compounds with vacancy disorder at nonmagnetic Cu sites: ${\mathrm{CuYbSe}}_2$ and ${\mathrm{Cu}}_{2.73}{\mathrm{YbP}}_2$. Single-crystal x-ray diffraction determines notable Cu-site vacancies in both materials. Unlike a single Cu site with 0.5 occupancy in ${\mathrm{CuYbSe}}_2, {\mathrm{Cu}}_{2.73}{\mathrm{YbP}}_2$ only presents 27% vacancies on one of three Cu sites. Magnetic susceptibility measurements indicate dominant antiferromagnetic interactions between ${\mathrm{Yb}}^{3+}$ ions. The effective magnetic moment is consistent with an effective spin-1/2 state of ${\mathrm{Yb}}^{3+}$. ${\mathrm{CuYbSe}}_2$ exhibits strong magnetic anisotropy between in-plane and out-of-plane directions with the estimated exchange interactions $J_a/k_{\mathrm{B}}=6.48\mathrm{K}$ and $J_c/k_{\mathrm{B}}=2.55\mathrm{K}$. No magnetic ordering is observed down to 0.4 K, supporting its quantum disordered ground state and candidacy as a quantum spin liquid. In contrast, ${\mathrm{Cu}}_{2.73}{\mathrm{YbP}}_2$ shows clear evidence of spin freezing at 4.5 K in both magnetization and heat capacity data, indicating a spin glass state. The field-induced magnetic orders are found in ${\mathrm{CuYbSe}}_2$. These results highlight the critical role of structural vacancies in perturbing Yb-based triangular lattices. We demonstrate that while the intrinsic Yb triangular lattices are comparable, the presence of Cu vacancies can fundamentally alter the magnetic ground state—tuning the system between quantum disordered and spin glass behavior.

The main objective of this work was to investigate how the orientation of polyisobutylene (PIB), employed in this study as a model system, affected shockwave behavior and, in particular, the kinematic $U_s-U_p$ hugoniot using MD simulations. There is a gap in knowledge on how the orientation of polymer chains in the shock direction influences the shockwave propagation and the state of shock compression behind the shockwave front. To achieve this objective, a fully equilibrated cubic amorphous cell (AC) consisting of 131 randomly oriented PIB chains with 60 repeat units was created first and used to simulate the $U_s-U_p$ hugoniot in unoriented control using the equilibrium MD multiscale shock technique (MSST), which a priori assumes that the Rankine-Hugoniot (RH) jump conditions are satisfied. Then, the cubic AC was stretched to form a long square prism. The stretching resulted in a strong orientation of the polymer chains along the long axis of the prism. After equilibration, this elongated AC was used to generate shockwaves at different piston velocities, $U_p$, by the nonequilibrium molecular dynamics (NEMD) method and to measure the corresponding shockwave velocities, $U_s$, and directly calculate the $U_s-U_p$ dependence. To ensure accurate calculation of the shockwave velocity $U_s$, a machine learning (ML) algorithm was used to automate and optimize multiple curve fittings of the shockwave profiles for various times. This protocol allowed unprecedentedly accurate measurements of the $U_s-U_p$ relationship for the oriented PIB system. It was shown that the $U_s-U_p$ shock hugoniots simulated for unoriented and oriented PIB systems overlapped perfectly in the range above 5 km/s but diverged noticeably more and more at lower $U_p$ values (1–5 km/s), with the $U_s$ values for the oriented system being larger for the same $U_p$. The rationale for this difference is discussed, including whether the RH conditions are satisfied for the oriented PIB system. This study also reports on the anisotropy of normal stresses (pressures) along the AC axes in the oriented system, the density behavior, and the behavior of intramolecular (angular, bond, dihedral) and intermolecular (pairwise) contributions to the total potential energy in oriented PIB behind a shock front in a compressed state.

We employed molecular-dynamics simulations to explore comparatively the thermomechanical behavior of two glass materials—an oxide silica glass (${\mathrm{SiO}}_2$) and a binary Cu-Zr-based metallic alloy (${\mathrm{Cu}}_{50}{\mathrm{Zr}}_{50}$)—during shear and elongation deformation cycles. By calculating the energy balance and tracking the temperature evolution of both glasses under deformation cycles, we are able to propose, for each of them, a constitutive law that accurately reproduces the self-heating process due to plastic deformation. These relatively simple constitutive laws involve strain rate sensitivity and a nonlinear temperature dependence of the thermal dilatancy coefficients, as well as strain gradient plasticity. To identify the right parameters, both glasses are equilibrated at very low temperature (10 K), and two independent deformation rates were applied to each sample for each type of deformation. Thermal attenuation is greatly amplified in silica compared to the metallic glass. Moreover, using a precise atomic description of the instantaneous deformation, combined with an exact coarse-graining procedure, we show, in silica, that self-heating is mainly supported by inhomogeneous strain gradient plasticity with nanometric characteristic lengthscales.

The observation of the interaction between two coupled effects of surface transfer doping (STD) and Burstein-Moss (B-M) shift on the electrical, optical, and electronic properties of ${\mathrm{V}}_2{\mathrm{O}}_5$, a layered van der Waals oxide semiconductor, is reported. Studies on bulk crystals, thin films, and powder samples show that, as a result of its high electron affinity, stoichiometric ${\mathrm{V}}_2{\mathrm{O}}_5$ exposed to humid air exhibits the phenomenon of surface transfer doping, in which a surface-absorbed water layer injects electrons into the conduction band (CB) of ${\mathrm{V}}_2{\mathrm{O}}_5$, leading to degenerate $n$-type doping, formation of a surface electron accumulation layer, and a corresponding B-M shift of the surface Fermi level of 0.25–0.6 eV well into the CB edge. In nonstoichiometric oxide (${\mathrm{V}}_2{\mathrm{O}}_{5-x}$), the presence of high density of bulk oxygen vacancy (${\mathrm{V}}_{\mathrm{O}}$) defects leads to electron doping, an increased B-M-induced $E_{\mathrm{F}}$ shift of 0.4–1.0 eV to higher energy in the bulk. In contrast, the surface $E_{\mathrm{F}}$ level remains pinned at lower energy owing to the switch in the STD effect, leading to reverse electron transfer from the oxide to the absorbed water layer, and causing the formation of an electron depletion layer on the surface. The implications of these effects for the wide variations in the reported band gap, doping, and catalysis of ${\mathrm{V}}_2{\mathrm{O}}_5$ are discussed.

Quantum magnetism based on the Kitaev honeycomb model has been intensively studied both by theoretical material design and experimental materialization. In contrast to the considerable progress of theoretical modeling and experiments on bulk crystals, it is still difficult to find a candidate material applicable to thin films and devices toward future quantum computation. Here we clearly demonstrate a Mott insulating state of $\mathrm{Ir}{\mathrm{O}}_6$ honeycomb monolayer structured in ilmenite-type $\mathrm{Mg}\text{−}\mathrm{Ir}\text{−}\mathrm{O}/\mathrm{MgTi}{\mathrm{O}}_3$ superlattices, which is a good candidate of the Kitaev honeycomb magnet applicable to devices. Electronic states detected by photoelectron spectroscopy agree well with those in theoretical band calculations. The stabilized superlattice with the Mott gap state is a promising platform to examine the device physics of the Majorana fermions and the $Z_2$ fluxes in the Kitaev honeycomb model, suggesting the thin-film techniques are quite beneficial for triggering the exploration of quantum computation in designable and evolvable heterostructures.