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<jats:p>The defect-related photoconductivity gain and persistent photoconductivity (PPC) observed in Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> Schottky photodetectors lead to a contradiction between high responsivity and fast recovery speed. In this work, a metal–semiconductor–metal (MSM) Schottky photodetector, a unidirectional Schottky photodetector, and a photoconductor were constructed on Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> films. The MSM Schottky devices have high gain (&gt; 13) and high responsivity (&gt; 2.5 A/W) at 230–250 nm, as well as slow recovery speed caused by PPC. Interestingly, applying a positive pulse voltage to the reverse-biased Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/Au Schottky junction can effectively suppress the PPC in the photodetector, while maintaining high gain. The mechanisms of gain and PPC do not strictly follow the interface trap trapping holes or the self-trapped holes models, which is attributed to the correlation with ionized oxygen vacancies in the Schottky junction. The positive pulse voltage modulates the width of the Schottky junction to help quickly neutralize electrons and ionized oxygen vacancies. The realization of suppression PPC functions and the establishment of physical models will facilitate the realization of high responsivity and fast response Schottky devices.</jats:p>

<jats:p>The U–Nb alloy, as a kind of nuclear material with good corrosion resistance and mechanical properties, plays an important role in the nuclear industry. However, the experimental measurements and theoretical calculations of many parameters which are essential in describing the dynamical properties of this alloy melt, including density, diffusivity, and viscosity, have not been carried out yet. The lack of data on the dynamical properties of nuclear materials seriously hinders the high-performance nuclear materials from being developed and applied. In this work, the dynamical properties of the U–Nb alloy melt are systematically studied by means of <jats:italic>ab initio</jats:italic> molecular dynamics simulations and their corresponding mathematical models are established, thereby being able to rapidly calculate the densities, diffusion coefficients, viscosities, and their activation energies in the whole U–Nb liquid region. This work provides a new idea for investigating the dynamical properties of binary alloy melts, thereby promoting the development of melt research.</jats:p>

<jats:p>Flower-like tungsten disulfide (WS<jats:sub>2</jats:sub>) with a diameter of 5–10 μm is prepared by chemical vapor deposition (CVD). Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Raman spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy are used to characterize its morphological and optical properties, and its growth mechanism is discussed. The key factors for the formation of flower-like WS<jats:sub>2</jats:sub> are determined. Firstly, the cooling process causes the generation of nucleation dislocations, and then the “leaf” growth of flower-like WS<jats:sub>2</jats:sub> is achieved by increasing the temperature.</jats:p>

<jats:p>We investigate the existence and dynamical stability of multipole gap solitons in Bose–Einstein condensate loaded in a deformed honeycomb optical lattice. Honeycomb lattices possess a unique band structure, the first and second bands intersect at a set of so-called Dirac points. Deformation can result in the merging and disappearance of the Dirac points, and support the gap solitons. We find that the two-dimensional honeycomb optical lattices admit multipole gap solitons. These multipoles can have their bright solitary structures being in-phase or out-of-phase. We also investigate the linear stabilities and nonlinear stabilities of these gap solitons. These results have applications of the localized structures in nonlinear optics, and may helpful for exploiting topological properties of a deformed lattice.</jats:p>

<jats:p>Interface can be a fertile ground for exotic quantum states, including topological superconductivity, Majorana mode, fractal quantum Hall effect, unconventional superconductivity, Mott insulator, etc. Here we grow single-unit-cell (1UC) FeTe film on NbSe<jats:sub>2</jats:sub> single crystal by molecular beam epitaxy (MBE) and investigate the film <jats:italic>in-situ</jats:italic> with a home-made cryogenic scanning tunneling microscopy (STM) and non-contact atomic force microscopy (AFM) combined system. We find different stripe-like superlattice modulations on grown FeTe film with different misorientation angles with respect to NbSe<jats:sub>2</jats:sub> substrate. We show that these stripe-like superlattice modulations can be understood as moiré pattern forming between FeTe film and NbSe<jats:sub>2</jats:sub> substrate. Our results indicate that the interface between FeTe and NbSe<jats:sub>2</jats:sub> is atomically sharp. By STM–AFM combined measurement, we suggest that the moiré superlattice modulations have an electronic origin when the misorientation angle is relatively small (≤ 3°) and have structural relaxation when the misorientation angle is relatively large (≥ 10°).</jats:p>

<jats:p>The interfacial enhanced ferromagnetism in maganite/ruthenate system is regarded as a promising path to broaden the potential of oxide-based electronic device applications. Here, we systematically studied the physical properties of La<jats:sub>1−<jats:italic>x</jats:italic> </jats:sub>Ca<jats:sub> <jats:italic>x</jats:italic> </jats:sub>MnO<jats:sub>3</jats:sub>/SrRuO<jats:sub>3</jats:sub> superlattices and compared them with the La<jats:sub>1−<jats:italic>x</jats:italic> </jats:sub>Ca<jats:sub> <jats:italic>x</jats:italic> </jats:sub>MnO<jats:sub>3</jats:sub> thin films and bulk compounds. The La<jats:sub>1−<jats:italic>x</jats:italic> </jats:sub>Ca<jats:sub> <jats:italic>x</jats:italic> </jats:sub>MnO<jats:sub>3</jats:sub>/SrRuO<jats:sub>3</jats:sub> superlattices exhibit significant enhancement of Curie temperature (<jats:italic>T</jats:italic> <jats:sub>C</jats:sub>) beyond the corresponding thin films and bulks. Based on these results, we constructed an extended phase diagram of La<jats:sub>1−<jats:italic>x</jats:italic> </jats:sub>Ca<jats:sub> <jats:italic>x</jats:italic> </jats:sub>MnO<jats:sub>3</jats:sub> under interfacial engineering. We considered the interfacial charge transfer and structural proximity effects as the origin of the interface-induced high <jats:italic>T</jats:italic> <jats:sub>C</jats:sub>. The structural characterizations revealed a pronounced increase of B–O–B bond angle, which could be the main driving force for the high <jats:italic>T</jats:italic> <jats:sub>C</jats:sub> in the superlattices. Our work inspires a deeper understanding of the collective effects of interfacial charge transfer and structural proximity on the physical properties of oxide heterostructures.</jats:p>

<jats:p>Manipulating metal–insulator transitions in strongly correlated materials is of great importance in condensed matter physics, with implications for both fundamental science and technology. Vanadium dioxide (VO<jats:sub>2</jats:sub>), as an ideal model system, is metallic at high temperatures and shown a typical metal–insulator structural phase transition at341 K from rutile structure to monoclinic structure. This behavior has been absorbed tons of attention for years. However, how to control this phase transition is still challenging and little studied. Here we demonstrated that to control the Ag nanonet arrays (NAs) in monoclinic VO<jats:sub>2</jats:sub>(M) could be effective to adjust this metal–insulator transition. With the increase of Ag NAs volume fraction by reducing the template spheres size, the transition temperature (<jats:italic>T</jats:italic> <jats:sub>c</jats:sub>) decreased from 68 ° C to 51 °C. The mechanism of <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> decrease was revealed as: the carrier density increases through the increase of Ag NAs volume fraction, and more free electrons injected into the VO<jats:sub>2</jats:sub> films induced greater absorption energy at the internal nanometal–semiconductor junction. These results supply a new strategy to control the metal–insulator transitions in VO<jats:sub>2</jats:sub>, which must be instructive for the other strongly correlated materials and important for applications.</jats:p>

<jats:p>Monolayer MnTe<jats:sub>2</jats:sub> stabilized as 1T structure has been theoretically predicted to be a two-dimensional (2D) ferromagnetic metal and can be tuned via strain engineering. There is no naturally van der Waals (vdW) layered MnTe<jats:sub>2</jats:sub> bulk, leaving mechanical exfoliation impossible to prepare monolayer MnTe<jats:sub>2</jats:sub>. Herein, by means of molecular beam epitaxy (MBE), we successfully prepared monolayer hexagonal MnTe<jats:sub>2</jats:sub> on Si(111) under Te rich condition. Sharp reflection high-energy electron diffraction (RHEED) and low-energy electron diffraction (LEED) patterns suggest the monolayer is atomically flat without surface reconstruction. The valence state of Mn<jats:sup>4+</jats:sup> and the atom ratio of ([Te]:[Mn]) further confirm the MnTe<jats:sub>2</jats:sub> compound. Scanning tunneling spectroscopy (STS) shows the hexagonal MnTe<jats:sub>2</jats:sub> monolayer is a semiconductor with a large bandgap of ∼ 2.78 eV. The valence-band maximum (VBM) locates at the <jats:italic>Γ</jats:italic> point, as illustrated by angle-resolved photoemission spectroscopy (ARPES), below which three hole-type bands with parabolic dispersion can be identified. The successful synthesis of monolayer MnTe<jats:sub>2</jats:sub> film provides a new platform to investigate the 2D magnetism.</jats:p>

<jats:p>We report the transport properties of a topological insulator candidate, LiMgBi. The electric resistivity of the title compound exhibits a metal-to-semiconductor-like transition at around 160 K and tends to saturation below 50 K. At low temperatures, the magnetoresistance is up to ∼260 % at 9 T and a clear weak antilocalization effect is observed in the low magnetic-field region. The Hall measurement reveals that LiMgBi is a multiband system, where hole-type carriers (<jats:italic>n</jats:italic> <jats:sub>h</jats:sub> ∼ 10<jats:sup>18</jats:sup> cm<jats:sup>−3</jats:sup>) play a major role in the transport process. Remarkably, LiMgBi possess a large Seebeck coefficient ∼440 μV/K) and a moderate thermal conductivity at room temperature, which indicate that LiMgBi is a promising candidate in thermoelectric applications.</jats:p>

<jats:p>AlN/GaN resonant tunneling diodes (RTDs) were grown separately on freestanding GaN (FS-GaN) substrates and sapphire substrates by plasma-assisted molecular-beam epitaxy (PA-MBE). Room temperature negative differential resistance (NDR) was obtained under forward bias for the RTDs grown on FS-GaN substrates, with the peak current densities (<jats:italic>J</jats:italic> <jats:sub>p</jats:sub>) of 175–700 kA/cm<jats:sup>2</jats:sup> and peak-to-valley current ratios (PVCRs) of 1.01–1.21. Two resonant peaks were also observed for some RTDs at room temperature. The effects of two types of substrates on epitaxy quality and device performance of GaN-based RTDs were firstly investigated systematically, showing that lower dislocation densities, flatter surface morphology, and steeper heterogeneous interfaces were the key factors to achieving NDR for RTDs.</jats:p>