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<jats:p>WC-Co reinforced C276 alloy composite coatings are fabricated on Q235 steel by laser melting deposition. The microstructure, hardness, wear performance, and electrochemical corrosion behavior of composite coating are studied. The results show that WC-Co particles are mostly uniformly distributed in the coating and provide favorable conditions for heterogeneous nucleation. The microstructure of C276/WC-Co composite coatings is composed of <jats:italic>γ</jats:italic>-Ni solid solution dendrites and MoNi solid solution eutectics. The WC-Co particles can effectively improve the hardness and wear resistance of C276 alloy. The average hardness of the composite coating containing 10-wt% WC-Co (447 HV<jats:sub>0.2</jats:sub>) are 1.26 times higher than that of the C276 alloy (356 HV<jats:sub>0.2</jats:sub>). The wear rate of composite coating containing 10-wt% WC-Co (6.95 × 10<jats:sup>−3</jats:sup> mg/m) is just 3.5% of that of C276 coating (196.23 × 10<jats:sup>−3</jats:sup> mg/m). However, comparing with Hastelloy C276, the corrosion resistance of C276/WC-Co composite coating decreases.</jats:p>

<jats:p>Constructing the hetrostructure is a feasible strategy to enhance the performances of photocatalysts. However, there are still some fundamental details and mechanisms for the specific design of photocatalysts with heterostructure, which need further confirming and explain. In this work, g-C<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub>-based heterostructures are constructed with TiO<jats:sub>2</jats:sub> in different ways, and their intrinsic factors to improve the photocatalytic activity are systematically studied by density functional theory (DFT). When g-C<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub> combines horizontally with TiO<jats:sub>2</jats:sub> to form a heterostructure, the interaction between them is dominated by van der Waals interaction. Although the recombination of photo-generated electron–hole pair cannot be inhibited significantly, this van der Waals interaction can regulate the electronic structures of the two components, which is conducive to the participation of photo-generated electrons and holes in the photocatalytic reaction. When the g-C<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub> combines vertically with TiO<jats:sub>2</jats:sub> to form a heterostructure, their interface states show obvious covalent features, which is very beneficial for the photo-generated electrons’ and holes’ transport along the opposite directions on both sides of the interface. Furthermore, the built-in electric field of g-C<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub>/TiO<jats:sub>2</jats:sub> heterostructure is directed from TiO<jats:sub>2</jats:sub> layer to g-C<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub> layer under equilibrium, so the photo-generated electron–hole pairs can be spatially separated from each other. These calculated results show that no matter how g-C<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub> and TiO<jats:sub>2</jats:sub> are combined together, the g-C<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub>/TiO<jats:sub>2</jats:sub> heterostructure can enhance the photocatalytic performance through corresponding ways.</jats:p>

<jats:p>Using the particle swarm optimization algorithm on structural search methods, we focus our crystal structures search on boron-rich alkali metal compounds of <jats:italic>M</jats:italic>B<jats:sub>12</jats:sub> (<jats:italic>M</jats:italic> = Be, Mg, Ca, Sr) with simulation cell sizes of 1–2 formula units (f.u.) at 0 GPa. The structure, electronic, and mechanical properties of <jats:italic>M</jats:italic>B<jats:sub>12</jats:sub> are obtained from the density functional theory using the plane-wave pseudopotential method within the generalized gradient approximations. The formation enthalpies of <jats:italic>M</jats:italic>B<jats:sub>12</jats:sub> regarding to solid metal <jats:italic>M</jats:italic> and solid alpha-boron suggested the predicted structures can be synthesized except for BeB<jats:sub>12</jats:sub>. The calculated band structures show <jats:italic>M</jats:italic>B<jats:sub>12</jats:sub> (<jats:italic>M</jats:italic> = Be, Mg, Ca, Sr) are all indirect semiconductors. All the calculated elastic constants of <jats:italic>M</jats:italic>B<jats:sub>12</jats:sub> satisfy the the mechanical stable conditions. The mechanical parameters (<jats:italic>i.e.</jats:italic>, bulk modulus, shear modulus, and Young’s modulus) are derived using the Voigt–Reuss–Hill method. The <jats:italic>G</jats:italic>/<jats:italic>B</jats:italic> ratios indicated that the <jats:italic>M</jats:italic>B<jats:sub>12</jats:sub> should exhibit brittle behavior. In addition, the hardness, Debye temperature, universal anisotropic index, and the percentage of anisotropy in compression and shear are also discussed in detail. We hope our results can inspire further experimental study on these boron-rich alkali-metal compounds.</jats:p>

<jats:p>Bulk metallic glasses (BMGs) with new chemical compositions (ZrCoAgAlNi) were fabricated and the effects of Ag minor addition on the glass forming ability (GFA) and crystallization kinetics were studied. The x-ray diffraction (XRD) test was applied to identify the amorphousness of BMGs or possible crystalline phases. Using differential scanning calorimeter (DSC), the thermal stability and crystallization kinetics under a non-isothermal condition at the different heating rates were studied. Considering the heating rate dependency of glass transition and crystallization kinetics, the activation energy was evaluated and measured for the mentioned processes. It was revealed that the rise in Ag content led to the decrease in activation energy for glass transition, while the activation energy for crystallization increased. The thermal stability and GFA were also studied and it was found that the Ag addition strongly affected the inherent features of BMGs. With the increase in Ag content, the atomic mobility and structural rearrangement changed in the material and consequently, the GFA and thermal stability were significantly improved.</jats:p>

<jats:p>The electric gating on the transport properties of two-dimensional electron gas (2DEG) at the interface of LaAlO<jats:sub>3</jats:sub>/SrTiO<jats:sub>3</jats:sub> (LAO/STO) heterostructure has attracted great research interest due to its potential application in field-effect devices. Most of previous works of gate effect were focused on the LAO/STO heterostructure containing only one conductive interface. Here, we systematically investigated the gate effect on high-quality LAO/STO superlattices (SLs) fabricated on the TiO<jats:sub>2</jats:sub>-terminated (001) STO substrates. In addition to the good metallicity of all SLs, we found that there are two types of charge carriers, the majority carriers and the minority carriers, coexisting in the SLs. The sheet resistance of the SLs with a fixed thickness of the LAO layer increases monotonically as the thickness of the STO layer increases. This is derived from the dependence of the minority carrier density on the thickness of STO. Unlike the LAO/STO heterostructure in which minority and majority carriers are simultaneously modulated by the gate effect, the minority carriers in the SLs can be tuned more significantly by the electric gating while the density of majority carriers is almost invariable. Thus, we consider that the minority carriers may mainly exist in the first interface near the STO substrate that is more sensitive to the back-gate voltage, and the majority carriers exist in the post-deposited STO layers. The SL structure provides the space separation for the multichannel conduction in the 2DEG, which opens an avenue for the design of field-effect devices based on LAO/STO heterostructure.</jats:p>

<jats:p>We report the edge-defined-film-fed (EFG)-grown <jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>-based Schottky photodiodes. The device has a reverse leakage current of ∼nA and a rectified ratio of ∼10<jats:sup>4</jats:sup> at ± 5 V. In addition, the photodiode detector shows a dark current of 0.3 pA, a photo-responsivity (<jats:italic>R</jats:italic>) of 2.875 mA/W, a special detectivity (<jats:italic>D</jats:italic> <jats:sup>*</jats:sup>) of 10<jats:sup>10</jats:sup> Jones, and an external quantum efficiency (EQE) of 1.4% at zero bias, illustrating a self-powered operation. This work may advance the development of the Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>-based Schottky diode solar-blind photodetectors.</jats:p>

<jats:p>We theoretically study the band structure and optical conductivity of twisted bilayer graphene (TBG) near the magic angle considering the effects of lattice relaxation. We show that the optical conductivity spectrum is characterized by a series of peaks associated with the van Hove singularities in the band structure, and the peak energies evolve systematically with the twist angle. Lattice relaxation effects in TBG modify its band structure, especially the flat bands, which leads to significant shifts of the peaks in the optical conductivity. These results demonstrate that spectroscopic features in the optical conductivity can serve as fingerprints for exploring the band structure, band gap, and lattice relaxation in magic-angle TBG as well as identifying its rotation angle.</jats:p>

<jats:p>We report the tip-induced superconductivity on the topological semimetal NbSb<jats:sub>2</jats:sub>, similar to the observation on TaAs<jats:sub>2</jats:sub> and NbAs<jats:sub>2</jats:sub>. Belonging to the same family of <jats:italic>MPn</jats:italic> <jats:sub>2</jats:sub>, all these materials possess similar band structures, indicating that the tip-induced superconductivity may be closely related to their topological nature and share a common mechanism. Further analysis suggests that a bulk band should play the dominant role in such local superconductivity most likely through interface coupling. In addition, the compatibility between the induced superconductivity and tips’ ferromagnetism gives an evidence for its unconventional nature. These results provide further clues to elucidate the mechanism of the tip-induced superconductivity observed in topological materials.</jats:p>

<jats:p>We review analytical and numerical studies of correlated insulating states in twisted bilayer graphene, focusing on real-space lattice models constructions and their unbiased quantum many-body solutions. We show that by constructing localized Wannier states for the narrow bands, the projected Coulomb interactions can be approximated by interactions of cluster charges with assisted nearest neighbor hopping terms. With the interaction part only, the Hamiltonian is <jats:italic>SU</jats:italic>(4) symmetric considering both spin and valley degrees of freedom. In the strong coupling limit where the kinetic terms are neglected, the ground states are found to be in the <jats:italic>SU</jats:italic>(4) manifold with degeneracy. The kinetic terms, treated as perturbation, break this large <jats:italic>SU</jats:italic>(4) symmetry and propel the appearance of intervalley coherent state, quantum topological insulators, and other symmetry-breaking insulating states. We first present the theoretical analysis of moiré lattice model construction and then show how to solve the model with large-scale quantum Monte Carlo simulations in an unbiased manner. We further provide potential directions such that from the real-space model construction and its quantum many-body solutions how the perplexing yet exciting experimental discoveries in the correlation physics of twisted bilayer graphene can be gradually understood. This review will be helpful for the readers to grasp the fast growing field of the model study of twisted bilayer graphene.</jats:p>

<jats:p>We grew a series of NaFe<jats:sub>1−<jats:italic>x</jats:italic> </jats:sub>V<jats:sub> <jats:italic>x</jats:italic> </jats:sub>As (0 ≤ <jats:italic>x</jats:italic> ≤ 0.03) single crystals and performed the measurements of resistance, magnetic susceptibility, and specific heat to study the superconducting phase diagram by doping V into NaFeAs. Both the structural and the spin-density-wave (SDW) transitions are slightly suppressed by V-doping. While superconducting transition temperature is enhanced to the maximum value of ∼ 15 K when the optimal doping level <jats:italic>x</jats:italic> = 0.007 and then is suppressed rapidly with further V-doping, displaying a small superconducting dome. Our results suggest that V-impurities should act as strong magnetic scattering centers which cause the sharp suppression of superconductivity in NaFe<jats:sub>1−<jats:italic>x</jats:italic> </jats:sub>V<jats:sub> <jats:italic>x</jats:italic> </jats:sub>As.</jats:p>