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<jats:p>The carbon diffusivity in tungsten is one fundamental and essential factor in the application of tungsten as plasma-facing materials for fusion reactors and substrates for diamond growth. However, data on this are quite scarce and largely scattered. We perform a series of first-principles calculations to predict the diffusion parameters of carbon in tungsten, and evaluate the effect of temperature on them by introducing lattice expansion and phonon vibration. The carbon atom prefers to occupy octahedral interstitial site rather than tetrahedral interstitial site, and the minimum energy path for its diffusion goes through a tetrahedral site. The temperature has little effect on the pre-exponential factor but a marked effect on the activation energy, which linearly increases with the temperature. Our predicted results are well consistent with the experimental data obtained at high temperature (&gt;1800 K) but significantly larger than the experimental results at low temperature (&lt;1800 K).</jats:p>

<jats:p>Density functional theory calculations are carried out to identify various configurations of oxygen molecules adsorbed on the Au-doped RuO<jats:sub>2</jats:sub> (110) surface. The binding energy calculations indicate that O<jats:sub>2</jats:sub> molecules are chemically adsorbed on the coordinatively unsaturated Ru (Ru<jats:sub>cus</jats:sub>) sites and the bridge oxygen vacancies on the Au sites. Transition state calculations show that O* can exist on the Ru<jats:sub>cus</jats:sub> site by <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{O}}}_{2}^{\ast }$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>2</mml:mn> <mml:mo>∗</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_11_116107_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> dissociation and diffusion. The calculations of the reaction path of CO indicate that the reaction energy barrier of CO adsorbed on Au with lattice oxygen decreases to 0.28 eV and requires less energy than that on the undoped structure.</jats:p>

<jats:p>The band structure, magnetism, charge distribution, and optics parameters of TMO<jats:sub>3</jats:sub>–h-BN hybrid systems are investigated by adopting first-principles study (FPS) calculations. It is observed that the TMO<jats:sub>3</jats:sub> clusters add finite magnetic moments to bilayer h-BN (BL/h-BN), thereby making it a magnetic two-dimensional (2D) material. Spin-polarized band structures for various TMO<jats:sub>3</jats:sub>–BL/h-BN hybrid models are calculated. After the incorporation of TMO<jats:sub>3</jats:sub>, BL/h-BN is converted into semimetal or conducting material in spin up/down bands, depending on the type of impurity cluster present in BL/h-BN lattice. Optics parameters are also investigated for the TMO<jats:sub>3</jats:sub>–BL/h-BN complex systems. The incorporation of TMO<jats:sub>3</jats:sub> clusters modifies the absorption and extinction coefficient in visible range, while static reflectivity and refraction parameter increase. It can be surmised that the TMO<jats:sub>3</jats:sub> substitution in BL/h-BN is a suitable technique to modify its physical parameters thus making it functional for nano/opto-electronic applications, and an experimental approach can be adapted to reinforce the outcomes of this study.</jats:p>

<jats:p>We review the recent progress in the study of topological phases in systems with space–time inversion symmetry <jats:italic>I</jats:italic> <jats:sub>ST</jats:sub>. <jats:italic>I</jats:italic> <jats:sub>ST</jats:sub> is an anti-unitary symmetry which is local in momentum space and satisfies <jats:inline-formula> <jats:tex-math> <?CDATA ${I}_{{\rm{ST}}}^{2}=1$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>I</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">ST</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_11_117101_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> such as <jats:italic>PT</jats:italic> in two dimensions (2D) and three dimensions (3D) without spin–orbit coupling and <jats:italic>C</jats:italic> <jats:sub>2</jats:sub> <jats:italic>T</jats:italic> in 2D with or without spin–orbit coupling, where <jats:italic>P</jats:italic>, <jats:italic>T</jats:italic>, <jats:italic>C</jats:italic> <jats:sub>2</jats:sub> indicate the inversion, time-reversal, and two-fold rotation symmetries, respectively. Under <jats:italic>I</jats:italic> <jats:sub>ST</jats:sub>, the Hamiltonian and the periodic part of the Bloch wave function can be constrained to be real-valued, which makes the Berry curvature and the Chern number vanish. In this class of systems, gapped band structures of real wave functions can be topologically distinguished by the Stiefel–Whitney numbers instead. The first and second Stiefel–Whitney numbers <jats:italic>w</jats:italic> <jats:sub>1</jats:sub> and <jats:italic>w</jats:italic> <jats:sub>2</jats:sub>, respectively, are the corresponding invariants in 1D and 2D, which are equivalent to the quantized Berry phase and the <jats:italic>Z</jats:italic> <jats:sub>2</jats:sub> monopole charge, respectively. We first describe the topological phases characterized by the first Stiefel–Whitney number, including 1D topological insulators with quantized charge polarization, 2D Dirac semimetals, and 3D nodal line semimetals. Next we review how the second Stiefel–Whitney class characterizes the 3D nodal line semimetals carrying a <jats:italic>Z</jats:italic> <jats:sub>2</jats:sub> monopole charge. In particular, we explain how the second Stiefel–Whitney number <jats:italic>w</jats:italic> <jats:sub>2</jats:sub>, the <jats:italic>Z</jats:italic> <jats:sub>2</jats:sub> monopole charge, and the linking number between nodal lines are related. Finally, we review the properties of 2D and 3D topological insulators characterized by the nontrivial second Stiefel Whitney class.</jats:p>

<jats:p>Hysteresis current–voltage (<jats:italic>I</jats:italic>–<jats:italic>V</jats:italic>) characteristics are often observed in a highly non-ideal (<jats:italic>n</jats:italic> &gt; 2) as-deposited nickel (Ni)/4H-SiC Schottky contact. However, we find that this kind of hysteresis effect also exists in an as-deposited Ni/n-type 4H-SiC Schottky structure even if the ideality factor (<jats:italic>n</jats:italic>) is less than 1.2. The hysteresis <jats:italic>I</jats:italic>–<jats:italic>V</jats:italic> characteristics is studied in detail in this paper by using the various measurements including the hysteresis <jats:italic>I</jats:italic>–<jats:italic>V</jats:italic>, sequential <jats:italic>I</jats:italic>–<jats:italic>V</jats:italic> sweeping, cycle <jats:italic>I</jats:italic>–<jats:italic>V</jats:italic>, constant reverse voltage stress (CRVS). The results show that the hysteresis <jats:italic>I</jats:italic>–<jats:italic>V</jats:italic> characteristics are strongly dependent on the sweeping voltage and post-deposition annealing (PDA). The high temperature PDA (800 °C) can completely eliminate this hysteresis. Meanwhile, the magnitude of the hysteresis effect is shown to decrease in the sequential <jats:italic>I</jats:italic>–<jats:italic>V</jats:italic> sweeping measurement, which is attributed to the fact that the electrons tunnel from the 4H-SiC to the localized states at the Ni/n-type 4H-SiC interface. It is found that the application of the reverse bias stress has little effect on the emission of those trapped electrons. And a fraction of the trapped electrons will be gradually released with the time under the condition of air and with no bias. The possible physical charging mechanism of the interface traps is discussed on the basis of the experimental findings.</jats:p>

<jats:p>We study ABA trilayer graphene under irradiation of a circularly polarized light. In high-frequency regime, the effective low-energy Hamiltonian is obtained based on the Floquet theory. With increasing circularly polarized light intensity, the band structure shows a band gap closing and reopening, which happen twice. The process of the band gap closing and reopening is accompanied with a topological phase transition. We investigate the Chern numbers and the anomalous Hall conductivities to confirm the topological phase transition. The interplay between light-induced circularity-dependent effective potential and effective sublattice potential is discussed.</jats:p>

<jats:p>Recently, the layered transition metal dichalcogenide 1T′ MoTe<jats:sub>2</jats:sub> has attracted considerable attention due to its non-saturating magnetoresistance, type-II Weyl semimetal properties, superconductivity, and potential candidate for two-dimensional (2D) topological insulator in the single- and few-layer limit. Here in this work, we perform systematic transport measurements on thin flakes of MoTe<jats:sub>2</jats:sub> prepared by mechanical exfoliation. We find that MoTe<jats:sub>2</jats:sub> flakes are superconducting and have an onset superconducting transition temperature <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> up to 5.3 K, which significantly exceeds that of its bulk counterpart. The in-plane upper critical field (<jats:italic>H</jats:italic> <jats:sub> <jats:italic>c</jats:italic>2||</jats:sub>) is much higher than the Pauli paramagnetic limit, implying that the MoTe<jats:sub>2</jats:sub> flakes have Zeeman-protected Ising superconductivity. Furthermore, the <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> and <jats:italic>H</jats:italic> <jats:sub> <jats:italic>c</jats:italic>2</jats:sub> can be tuned by up to 320 mK and 400 mT by applying a gate voltage. Our result indicates that MoTe<jats:sub>2</jats:sub> flake is a good candidate for studying exotic superconductivity with nontrivial topological properties.</jats:p>

<jats:p>In the last few years, charge order and its entanglement with superconductivity are under hot debate in high-<jats:italic>T</jats:italic> <jats:sub>c</jats:sub> community due to the new progress on charge order in high-<jats:italic>T</jats:italic> <jats:sub>c</jats:sub> cuprate superconductors YBa<jats:sub>2</jats:sub>Cu<jats:sub>3</jats:sub>O<jats:sub>6+<jats:italic>x</jats:italic> </jats:sub>. Here, we will briefly introduce the experimental status of this field and mainly focus on the experimental progress of high-field nuclear magnetic resonance (NMR) study on charge order in YBa<jats:sub>2</jats:sub>Cu<jats:sub>3</jats:sub>O<jats:sub>6+<jats:italic>x</jats:italic> </jats:sub>. The pioneering high-field NMR work in YBa<jats:sub>2</jats:sub>Cu<jats:sub>3</jats:sub>O<jats:sub>6+<jats:italic>x</jats:italic> </jats:sub> sets a new stage for studying charge order which has become a ubiquitous phenomenon in high-<jats:italic>T</jats:italic> <jats:sub>c</jats:sub> cuprate superconductors.</jats:p>

<jats:p>We consider a highly unconventional superconducting state with chiral d-wave symmetry in doped graphene under strain with the Gutzwiller–RVB method in the momentum space. It is shown that flat bands emerge in the normal state for reasonable strain. As a result, the superconducting critical temperature is found to be linearly proportional to the strength of the electron–electron interaction. Furthermore, the chiral d-wave superconducting state is shown with coexistence of the charge density wave and the pair density wave. There are different coexisting states with those orders under different doping levels.</jats:p>

<jats:p>The crystal structures, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase Pr<jats:sub>1 − <jats:italic>x</jats:italic> </jats:sub> <jats:italic>Tb<jats:sub>x</jats:sub> </jats:italic>Fe<jats:sub>1.9</jats:sub> compounds are investigated in a temperature range between 5 K and 300 K. High resolution synchrotron x-ray diffraction (XRD) analysis shows that different proportions of Tb in Pr<jats:sub>1 − <jats:italic>x</jats:italic> </jats:sub>Tb<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Fe<jats:sub>1.9</jats:sub> alloys can result in different easy magnetization directions (EMD) below 70 K, <jats:italic>i.e.</jats:italic>, [100] with <jats:italic>x</jats:italic> = 0.0, and [111] with <jats:italic>x</jats:italic> ≥ 0.1. This indicates Tb substitution can lead the EMD to change from [100] to [111] with <jats:italic>x</jats:italic> rising from 0.0 up to 0.1. The Tb substitution for Pr reduces the saturation magnetization <jats:italic>M</jats:italic> <jats:sub>s</jats:sub> and the magnetostriction to their minimum value when <jats:italic>x</jats:italic> = 0.6, but it can increase low-field (0 ≤ <jats:italic>H</jats:italic> ≤ 9 kOe, the unit 1 Oe = 79.5775 A · m<jats:sup>−1</jats:sup>) magnetostriction when <jats:italic>x</jats:italic> = 0.8 and 1.0 at 5 K. This can be attributed to the larger magnetostriction of PrFe<jats:sub>1.9</jats:sub> than that of TbFe<jats:sub>1.9</jats:sub>, as well as the decrease of the resulting anisotropy due to Tb substitution at low temperatures.</jats:p>