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<jats:p>Layered lanthanum silver antimonide LaAgSb<jats:sub>2</jats:sub> exhibits both charge density wave (CDW) order and Dirac-cone-like band structure at ambient pressure. Here, we systematically investigate the pressure evolution of structural and electronic properties of LaAgSb<jats:sub>2</jats:sub> single crystal. We show that the CDW order is destabilized under compression, as evidenced by the gradual suppression of magnetoresistance. At <jats:italic>P</jats:italic> <jats:sub>C</jats:sub> ∼ 22 GPa, synchrotron x-ray diffraction and Raman scattering measurements reveal a structural modification at room-temperature. Meanwhile, the sign change of the Hall coefficient is observed at 5 K. Our results demonstrate the tunability of CDW order in the pressurized LaAgSb<jats:sub>2</jats:sub> single crystal, which can be helpful for its potential applications in the next-generation devices.</jats:p>

<jats:p>Based on density functional first-principles calculations and anisotropic Eliashberg equations, we have investigated the electronic structure, lattice dynamics, and phonon-mediated superconductivity in newly synthesized layered compound SrBC under pressure. Different from LiBC and MgB<jats:sub>2</jats:sub>, our calculations surprisingly reveal that SrBC is isotropic in compressibility, due to the accumulation of substantial electrons in the interstitial region. We find that the Sr phonons strongly couple with B-2p<jats:sub> <jats:italic>z</jats:italic> </jats:sub> orbital and the interstitial states, giving rise to a two-gap superconductivity in SrBC, whose transition temperature shows an inverted V-shaped dependence on pressure. The maximal transition temperature is about 22 K at 50 GPa. On both sides of 50 GPa, the transition temperature exhibits quasi-linear variation with positive and negative slopes, respectively. Such a variation of transition temperature is infrequent among phonon-mediated superconductors. The competition between enhanced electron–phonon matrix element and hardened phonons plays an essential role in governing the behavior of the critical temperature.</jats:p>

<jats:p>The three halogen solids (Cl<jats:sub>2</jats:sub>, Br<jats:sub>2</jats:sub>, and I<jats:sub>2</jats:sub>) have the isostructural diatomic molecular phase I with a space group of <jats:italic>Cmca</jats:italic> at ambient pressure. At high pressure, they all go through an intermediate phase V with incommensurate structures before eventually dissociating into the monatomic phase II. However, a new structural transition between phase I and V with anomalous bond-length behavior was observed in bromine under pressure, which, so far, has not been confirmed in iodine and chlorine. Here, we perform first-principles calculations for iodine and chlorine. The new structural transition was predicted to be common to all three halogens under pressure. The transition pressures might be systematically underestimated by the imperfect van der Waals correction method, but they follow the order Cl<jats:sub>2</jats:sub> &gt; Br<jats:sub>2</jats:sub> &gt; I<jats:sub>2</jats:sub>, which is consistent with other pressure-induced structural transitions such as metallization and the molecular-to-monatomic transition.</jats:p>

<jats:p>By using first-principles calculation, we study the properties of h-BN/BC<jats:sub>3</jats:sub> heterostructure and the effects of external electric fields and strains on its electronic and optical properties. It is found that the semiconducting h-BN/BC<jats:sub>3</jats:sub> has good dynamical stability and ultrahigh stiffness, enhanced electron mobility, and well-preserved electronic band structure as the BC<jats:sub>3</jats:sub> monolayer. Meanwhile, its electronic band structure is slightly modified by an external electric field. In contrast, applying an external strain can mildly modulate the electronic band structure of h-BN/BC<jats:sub>3</jats:sub> and the optical property exhibits an apparent redshift under a compressive strain relative to the pristine one. These findings show that the h-BN/BC<jats:sub>3</jats:sub> hybrid can be designed as optoelectronic device with moderately strain-tunable electronic and optical properties.</jats:p>

<jats:p>The room-temperature (RT) bonding mechanisms of GaAs/SiO<jats:sub>2</jats:sub>/Si and GaAs/Si heterointerfaces fabricated by surface-activated bonding (SAB) are investigated using a focused ion beam (FIB) system, cross-sectional scanning transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX) and scanning acoustic microscopy (SAM). According to the element distribution detected by TEM and EDX, it is found that an intermixing process occurs among different atoms at the heterointerface during the RT bonding process following the surface-activation treatment. The diffusion of atoms at the interface is enhanced by the point defects introduced by the process of surface activation. We can confirm that through the point defects, a strong heterointerface can be created at RT. The measured bonding energies of GaAs/SiO<jats:sub>2</jats:sub>/Si and GaAs/Si wafers are 0.7 J/m<jats:sup>2</jats:sup> and 0.6 J/m<jats:sup>2</jats:sup>. The surface-activation process can not only remove surface oxides and generate dangling bonds, but also enhance the atomic diffusivity at the interface.</jats:p>

<jats:p>We study the topological properties of the one-dimensional non-Hermitian Kitaev model with complex either periodic or quasiperiodic potentials. We obtain the energy spectrum and the phase diagrams of the system by using the transfer matrix method as well as the topological invariant. The phase transition points are given analytically. The Majorana zero modes in the topological nontrivial regimes are obtained. Focusing on the quasiperiodic potential, we obtain the phase transition from the topological superconducting phase to the Anderson localization, which is accompanied with the Anderson localization–delocalization transition in this non-Hermitian system. We also find that the topological regime can be reduced by increasing the non-Hermiticity.</jats:p>

<jats:p>Owing to the interaction between the layers, the twisted bilayer two-dimensional (2D) materials exhibit numerous unique optical and electronic properties different from the monolayer counterpart, and have attracted tremendous interests in current physical research community. By means of first-principles and tight-binding model calculations, the electronic properties of twisted bilayer biphenylene carbon (BPC) are systematically investigated in this paper. The results indicate that the effect of twist will not only leads to a phase transition from semiconductor to metal, but also an adjustable band gap in BPC (0 meV to 120 meV depending on the twist angle). Moreover, unlike the twisted bilayer graphene (TBG), the flat bands in twisted BPC are no longer restricted by “magic angles”, <jats:italic>i.e.</jats:italic>, abnormal flat bands could be appeared as well at several specific large angles in addition to the small angles. The charge density of these flat bands possesses different local modes, indicating that they might be derived from different stacked modes and host different properties. The exotic physical properties presented in this work foreshow twisted BPC a promising material for the application of terahertz and infrared photodetectors and the exploration of strong correlation.</jats:p>

<jats:p>The physics of flat band is novel and rich but difficult to access. In this regard, recently twisting of bilayer van der Waals (vdW)-bounded two-dimensional (2D) materials has attracted much attention, because the reduction of Brillouin zone will eventually lead to a diminishing kinetic energy. Alternatively, one may start with a 2D kagome lattice, which already possesses flat bands at the Fermi level, but unfortunately these bands connect quadratically to other (dispersive) bands, leading to undesirable effects. Here, we propose, by first-principles calculation and tight-binding modeling, that the same bilayer twisting approach can be used to isolate the kagome flat bands. As the starting kinetic energy is already vanishingly small, the interlayer vdW potential is always sufficiently large irrespective of the twisting angle. As such the electronic states in the (connected) flat bands become unstable against a spontaneous Wigner crystallization, which is expected to have interesting interplays with other flat-band phenomena such as novel superconductivity and anomalous quantum Hall effect.</jats:p>

<jats:p>Localized surface plasmon has been extensively studied and used for the photocatalysis of various chemical reactions. However, the different contributions between plasmon resonance and interband transition in photocatalysis has not been well understood. Here, we study the photothermal and hot electrons effects for crystal transformation by combining controlled experiments with numerical simulations. By photo-excitation of NaYF<jats:sub>4</jats:sub> : Eu<jats:sup>3+</jats:sup> @Au composite structure, it is found that the plasmonic catalysis is much superior to that of interband transition in the experiments, owing to the hot electrons generated by plasmon decay more energetic to facilitate the reaction. We emphasize that the energy level of hot electrons plays an essential role for improving the photocatalytic activity. The results provide guidelines for improving the efficiency of plasmonic catalysis in future experimental design.</jats:p>

<jats:p>Two-dimensional electron gases (2DEGs) formed at the interface between two oxide insulators present a promising platform for the exploration of emergent phenomena. While most of the previous works focused on SrTiO<jats:sub>3</jats:sub>-based 2DEGs, here we took the amorphous-ABO<jats:sub>3</jats:sub>/KTaO<jats:sub>3</jats:sub> system as the research object to study the relationship between the interface conductivity and the redox property of B-site metal in the amorphous film. The criterion of oxide–oxide interface redox reactions for the B-site metals, Zr, Al, Ti, Ta, and Nb in conductive interfaces was revealed: the formation heat of metal oxide, <jats:inline-formula> <jats:tex-math><?CDATA $\Delta {H}_{{\rm{f}}}^{{\rm{o}}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>Δ</mml:mo> <mml:msubsup> <mml:mi>H</mml:mi> <mml:mi mathvariant="normal">f</mml:mi> <mml:mi mathvariant="normal">o</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_7_077302_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, is lower than –350 kJ/(mol O) and the work function of the metal <jats:italic>Φ</jats:italic> is in the range of 3.75 eV &lt; <jats:italic>Φ</jats:italic> &lt; 4.4 eV. Furthermore, we found that the smaller absolute value of <jats:inline-formula> <jats:tex-math><?CDATA $\Delta {H}_{{\rm{f}}}^{{\rm{o}}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>Δ</mml:mo> <mml:msubsup> <mml:mi>H</mml:mi> <mml:mi mathvariant="normal">f</mml:mi> <mml:mi mathvariant="normal">o</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_7_077302_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and the larger value of <jats:italic>Φ</jats:italic> of the B-site metal would result in higher mobility of the two-dimensional electron gas that formed at the corresponding amorphous-ABO<jats:sub>3</jats:sub>/KTaO<jats:sub>3</jats:sub> interface. This finding paves the way for the design of high-mobility all-oxide electronic devices.</jats:p>