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<jats:p>We performed calculations of the electronic band structure and the Fermi surface, measured the longitudinal resistivity <jats:italic>ρ<jats:sub>xx</jats:sub> </jats:italic>(<jats:italic>T</jats:italic>,<jats:italic>H</jats:italic>), Hall resistivity <jats:italic>ρ<jats:sub>xy</jats:sub> </jats:italic>(<jats:italic>T</jats:italic>,<jats:italic>H</jats:italic>), and magnetic susceptibility as a function of temperature at various magnetic fields for VAs<jats:sub>2</jats:sub> with a monoclinic crystal structure. The band structure calculations show that VAs<jats:sub>2</jats:sub> is a nodal-line semimetal when spin-orbit coupling is ignored. The emergence of a minimum at around 11 K in <jats:italic>ρ<jats:sub>xx</jats:sub> </jats:italic>(<jats:italic>T</jats:italic>) measured at <jats:italic>H</jats:italic> = 0 demonstrates that some additional magnetic impurities (V<jats:sup>4+</jats:sup>, <jats:italic>S</jats:italic> = 1/2) exist in VAs<jats:sub>2</jats:sub> single crystals, inducing Kondo scattering, evidenced by both the fitting of <jats:italic>ρ<jats:sub>xx</jats:sub> </jats:italic>(<jats:italic>T</jats:italic>) data and the susceptibility measurements. It is found that a large positive magnetoresistance (MR) reaching 649% at 10 K and 9 T, its nearly quadratic field dependence, and a field-induced up-turn behavior of <jats:italic>ρ<jats:sub>xx</jats:sub> </jats:italic>(<jats:italic>T</jats:italic>) also emerge in VAs<jats:sub>2</jats:sub>, although MR is not so large due to the existence of additional scattering compared with other topological nontrivial/trivial semimetals. The observed properties are attributed to a perfect charge-carrier compensation, which is evidenced by both the calculations relying on the Fermi surface and the Hall resistivity measurements. These results indicate that the compounds containing V (3<jats:italic>d</jats:italic> <jats:sup>3</jats:sup> 4<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>) element can be as a platform for studying the influence of magnetic impurities to the topological properties.</jats:p>

<jats:p>The electronic topology is generally related to the Berry curvature, which can induce the anomalous Hall effect in time-reversal symmetry breaking systems. Intrinsic monolayer transition metal dichalcogenides possesses two nonequivalent <jats:italic>K</jats:italic> and <jats:italic>K</jats:italic>′ valleys, having Berry curvatures with opposite signs, and thus vanishing anomalous Hall effect in this system. Here we report the experimental realization of asymmetrical distribution of Berry curvature in a single valley in monolayer WSe<jats:sub>2</jats:sub> via applying uniaxial strain to break <jats:italic>C</jats:italic> <jats:sub>3<jats:italic>v</jats:italic> </jats:sub> symmetry. As a result, although the Berry curvature itself is still opposite in <jats:italic>K</jats:italic> and <jats:italic>K</jats:italic>′ valleys, the two valleys would contribute equally to nonzero Berry curvature dipole. Upon applying electric field <jats:italic> <jats:bold>E</jats:bold> </jats:italic>, the emergent Berry curvature dipole <jats:italic> <jats:bold>D</jats:bold> </jats:italic> would lead to an out-of-plane orbital magnetization <jats:italic>M</jats:italic> ∝ <jats:italic> <jats:bold>D</jats:bold> </jats:italic> ⋅ <jats:italic> <jats:bold>E</jats:bold> </jats:italic>, which further induces an anomalous Hall effect with a linear response to <jats:italic>E</jats:italic> <jats:sup>2</jats:sup>, known as nonlinear Hall effect. We show the strain modulated transport properties of nonlinear Hall effect in monolayer WSe<jats:sub>2</jats:sub> with moderate hole-doping by gating. The second-harmonic Hall signals show quadratic dependence on electric field, and the corresponding orbital magnetization per current density <jats:italic>M</jats:italic>/<jats:italic>J</jats:italic> can reach as large as 60. In contrast to the conventional Rashba–Edelstein effect with in-plane spin polarization, such current-induced orbital magnetization is along the out-of-plane direction, thus promising for high-efficient electrical switching of perpendicular magnetization.</jats:p>

<jats:p>Electrides are unique materials, whose anionic electrons are confined to interstitial voids, and they have broad potential applications in various areas. In contrast to the majority of inorganic electrides, in which the anionic electrons primarily consist of <jats:italic>s</jats:italic>-electrons of metals, electrides with anionic <jats:italic>d</jats:italic>-electrons are very rare. Based on first-principles electronic structure calculations, we predict that the layered transition metal chalcogenide Hf<jats:sub>2</jats:sub>Se is a novel electride candidate with anionic <jats:italic>d</jats:italic>-electrons. Our results indicate that the anionic electrons confined in the Hf<jats:sub>6</jats:sub> octahedra vacancy between [Hf<jats:sub>2</jats:sub>Se] layers mainly come from the Hf-5<jats:italic>d</jats:italic> orbitals. In addition, the anionic electrons coexist with the Hf–Hf multiple-center metallic bonds located in the center of neighboring Hf<jats:sub>4</jats:sub> tetrahedra. The calculated work function (3.33 eV) for the (110) surface of Hf<jats:sub>2</jats:sub>Se is slightly smaller than that of Hf<jats:sub>2</jats:sub>S, which has recently been reported to exhibit good electrocatalytic performance. Our study of Hf<jats:sub>2</jats:sub>Se will enrich the electride family, and promote further research into the physical properties and applications of electrides.</jats:p>

<jats:p>Unconventional superconductivity, in particular, in noncentrosymmetric systems, has been a long-sought topic in condensed matter physics. Recently, Re-based superconductors have attracted great attention owing to the potential time-reversal symmetry breaking in their superconducting states. We report the superconducting properties of noncentrosymmetric compounds Ta<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Re<jats:sub>1 – <jats:italic>x</jats:italic> </jats:sub> with 0.1 ≤ <jats:italic>x</jats:italic> ≤ 0.25, and find that the superconducting transition temperature reaches a maximum of ∼8 K at the optimal level <jats:italic>x</jats:italic> = 0.15. Nevertheless, muon-spin rotation and relaxation measurements reveal no time-reversal symmetry breaking existing in its superconducting state, which is in sharp contrast to both centrosymmetric Re metal and many other noncentrosymmetric Re-based superconductors.</jats:p>

<jats:p>We show that the layered-structure BaCuS<jats:sub>2</jats:sub> is a moderately correlated electron system in which the electronic structure of the CuS layer bears a resemblance to those in both cuprates and iron-based superconductors. Theoretical calculations reveal that the in-plane <jats:italic>d</jats:italic>–<jats:italic>p σ</jats:italic> <jats:sup>*</jats:sup>-bonding bands are isolated near the Fermi level. As the energy separation between the <jats:italic>d</jats:italic> and <jats:italic>p</jats:italic> orbitals are much smaller than those in cuprates and iron-based superconductors, BaCuS<jats:sub>2</jats:sub> is expected to be moderately correlated. We suggest that this material is an ideal system to study the competitive/collaborative nature between two distinct superconducting pairing mechanisms, namely the conventional BCS electron-phonon interaction and the electron-electron correlation, which may be helpful to establish the elusive mechanism of unconventional high-temperature superconductivity.</jats:p>

<jats:p>The unipolar diode-like domain wall currents in LiNbO<jats:sub>3</jats:sub> single-crystal nanodevices are not only attractive in terms of their applications in nonvolatile ferroelectric domain wall memory, but also useful in half-wave and full-wave rectifier systems, as well as detector, power protection, and steady voltage circuits. Unlike traditional diodes, where the rectification functionality arises from the contact between n-type and p-type conductors, which are unchanged after off-line production, ferroelectric domain wall diodes can be reversibly created, erased, positioned, and shaped, using electric fields. We demonstrate such functionality using ferroelectric mesa-like cells, formed at the surface of an insulating <jats:italic>X</jats:italic>-cut LiNbO<jats:sub>3</jats:sub> single crystal. Under the application of an in-plane electric field above a coercive field along the polar <jats:italic>Z</jats:italic> axis, the domain within the cell is reversed to be antiparallel to the unswitched bottom domain via the formation of a conducting domain wall. The wall current was rectified using two interfacial volatile domains in contact with two side Pt electrodes. Unlike the nonvolatile inner domain wall, the interfacial domain walls disappear to turn off the wall current path after the removal of the applied electric field, or under a negative applied voltage, due to the built-in interfacial imprint fields. These novel devices have the potential to facilitate the random definition of diode-like elements in modern large-scale integrated circuits.</jats:p>

<jats:p>Considering that pressure-induced formation of short, strong covalent bonds in light-element compounds can produce superhard materials, we employ structure searching and first-principles calculations to predict a new class of boron nitrides with a stoichiometry of BN<jats:sub>2</jats:sub>, which are stable relative to alpha-B and alpha-N<jats:sub>2</jats:sub> at ambient pressure. At ambient pressure, the most stable phase has a layered structure (h-BN<jats:sub>2</jats:sub>) containing hexagonal BN layers between which there are intercalated N<jats:sub>2</jats:sub> molecules. At 25 GPa, a three-dimensional <jats:italic>P</jats:italic>4<jats:sub>2</jats:sub>/<jats:italic>mmc</jats:italic> structure with single N–N bonds becomes the most stable. Dynamical, thermal, and mechanical stability calculations reveal that this structure can be recovered under ambient conditions. Its calculated stress-strain relations demonstrate an intrinsic superhard nature with an estimated Vickers hardness of ∼43 GPa. This structure has a potentially high energy density of ∼4.19 kJ/g.</jats:p>

<jats:p>The spread of the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has become a global health crisis. The binding affinity of SARS-CoV-2 (in particular the receptor binding domain, RBD) to its receptor angiotensin converting enzyme 2 (ACE2) and the antibodies is of great importance in understanding the infectivity of COVID-19 and evaluating the candidate therapeutic for COVID-19. We propose a new method based on molecular mechanics/Poisson–Boltzmann surface area (MM/PBSA) to accurately calculate the free energy of SARS-CoV-2 RBD binding to ACE2 and antibodies. The calculated binding free energy of SARS-CoV-2 RBD to ACE2 is –13.3 kcal/mol, and that of SARS-CoV RBD to ACE2 is –11.4 kcal/mol, which agree well with the experimental results of –11.3 kcal/mol and –10.1 kcal/mol, respectively. Moreover, we take two recently reported antibodies as examples, and calculate the free energy of antibodies binding to SARS-CoV-2 RBD, which is also consistent with the experimental findings. Further, within the framework of the modified MM/PBSA, we determine the key residues and the main driving forces for the SARS-CoV-2 RBD/CB6 interaction by the computational alanine scanning method. The present study offers a computationally efficient and numerically reliable method to evaluate the free energy of SARS-CoV-2 binding to other proteins, which may stimulate the development of the therapeutics against the COVID-19 disease in real applications.</jats:p>

<jats:p>Thermal concentrators and cloaks with ellipsoidal shapes are designed by utilizing the transformation thermotics method and finite element simulations. The thermal conductivities for the concentrator and cloak are directly derive in Cartesian coordinates. The simulation results show that the ellipsoidal thermal concentrator can focus heat flux into a central region and that the ellipsoidal thermal cloak can guide heat flux around the cloaked region smoothly without disturbing the external temperature distribution and heat flux. The present method can be extended to design arbitrarily shaped thermal metadevices with novel properties.</jats:p>