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<jats:p>A plasmonic resonator system consisting of a metal–insulator–metal waveguide and a Q-shaped resonant cavity is proposed in this paper. The transmission properties of surface plasmon polaritons in this structure are investigated by using the finite difference in time domain (FDTD) method, and the simulation results contain two resonant dips. The physical mechanism is studied by the multimode interference coupled mode theory (MICMT), and the theoretical results are in highly consistent with the simulation results. Furthermore, the parameters of the Q-shaped cavity can be controlled to adjust the two dips, respectively. The refractive index sensor proposed in this paper, with a sensitivity of 1578 nm/RIU and figure of merit (FOM) of 175, performs better than most of the similar structures. Therefore, the results of the study are instructive for the design and application of high sensitivity nanoscale refractive index sensors.</jats:p>

<jats:p>The application of magnetic fields, electric fields, and the increase of the electromagnetic wave frequency are up-and-coming solutions for the blackout problem. Therefore, this study considers the influence of the external magnetic field on the electron flow and the effect of the external electric field on the electron density distribution, and uses the scattering matrix method (SMM) to perform theoretical calculations and analyze the transmission behavior of terahertz waves under different electron densities, magnetic field distributions, and collision frequencies. The results show that the external magnetic field can improve the transmission of terahertz waves at the low-frequency end. Magnetizing the plasma from the direction perpendicular to the incident path can optimize the right-hand polarized wave transmission. The external electric field can increase the transmittance to some extent, and the increase of the collision frequency can suppress the right-hand polarized wave cyclotron resonance caused by the external magnetic field. By adjusting these parameters, it is expected to alleviate the blackout phenomenon to a certain extent.</jats:p>

<jats:p>Rayleigh–Taylor instability (RTI) of finite-thickness shell plays an important role in deep understanding the characteristics of shell deformation and material mixing. The RTI of a finite-thickness fluid layer is studied analytically considering an arbitrary perturbation phase difference on the two interfaces of the shell. The third-order weakly nonlinear (WN) solutions for RTI are derived. It is found the main feature (bubble-spike structure) of the interface is not affected by phase difference. However, the positions of bubble and spike are sensitive to the initial phase difference, especially for a thin shell (<jats:italic>kd</jats:italic> &lt; 1), which will be detrimental to the integrity of the shell. Furthermore, the larger phase difference results in much more serious RTI growth, significant shell deformation can be obtained in the WN stage for perturbations with large phase difference. Therefore, it should be considered in applications where the interface coupling and perturbation phase effects are important, such as inertial confinement fusion.</jats:p>

<jats:p>When the GaAs/AlGaAs superlattice-based devices are used under irradiation environments, point defects may be created and ultimately deteriorate their electronic and transport properties. Thus, understanding the properties of point defects like vacancies and interstitials is essential for the successful application of semiconductor materials. In the present study, first-principles calculations are carried out to explore the stability of point defects in GaAs/Al<jats:sub>0.5</jats:sub>Ga<jats:sub>0.5</jats:sub>As superlattice and their effects on electronic properties. The results show that the interstitial defects and Frenkel pair defects are relatively difficult to form, while the antisite defects are favorably created generally. Besides, the existence of point defects generally modifies the electronic structure of GaAs/Al<jats:sub>0.5</jats:sub>Ga<jats:sub>0.5</jats:sub>As superlattice significantly, and most of the defective SL structures possess metallic characteristics. Considering the stability of point defects and carrier mobility of defective states, we propose an effective strategy that Al<jats:sub>As</jats:sub>, Ga<jats:sub>As</jats:sub>, and Al<jats:sub>Ga</jats:sub> antisite defects are introduced to improve the hole or electron mobility of GaAs/Al<jats:sub>0.5</jats:sub>Ga<jats:sub>0.5</jats:sub>As superlattice. The obtained results will contribute to the understanding of the radiation damage effects of the GaAs/AlGaAs superlattice, and provide a guidance for designing highly stable and durable semiconductor superlattice-based electronics and optoelectronics for extreme environment applications.</jats:p>

<jats:p>The study of boron structure is fascinating because boron has various allotropes containing boron icosahedrons under pressure. Here, we propose a new boron structure (space group <jats:inline-formula> <jats:tex-math><?CDATA $Fm\bar{3}m$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>F</mml:mi> <mml:mi>m</mml:mi> <mml:mover accent="true"> <mml:mn>3</mml:mn> <mml:mo stretchy="false">¯</mml:mo> </mml:mover> <mml:mi>m</mml:mi> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_3_036301_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) that is dynamically stable at 1.4 tera-Pascal (TPa) using density functional theory and an evolutionary algorithm. The unit cell of this structure can be viewed as a structure with a boron atom embedded in the icosahedron. This structure behaves as a metal, and cannot be stable under ambient pressure. Furthermore, we found electrons gather in lattice interstices, which is similar to that of the semiconductor Na or Ca<jats:sub>2</jats:sub>N-II under high pressure. The discovery of this new structure expands our comprehension of high-pressure condensed matter and contributes to the further development of high-pressure science.</jats:p>

<jats:p>Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and <jats:italic>ab initio</jats:italic> calculation, we investigate the electronic structure of Cu<jats:sub>2</jats:sub>Tl<jats:italic>X</jats:italic> <jats:sub>2</jats:sub> (<jats:italic>X</jats:italic> = Se, Te), ternary transition metal chalcogenides with quasi-two-dimensional crystal structure. The band dispersions near the Fermi level are mainly contributed by the Te/Se p orbitals. According to our <jats:italic>ab-initio</jats:italic> calculation, the electronic structure changes from a semiconductor with indirect band gap in Cu<jats:sub>2</jats:sub>TlSe<jats:sub>2</jats:sub> to a semimetal in Cu<jats:sub>2</jats:sub>TlTe<jats:sub>2</jats:sub>, suggesting a band-gap tunability with the composition of Se and Te. By comparing ARPES experimental data with the calculated results, we identify strong modulation of the band structure by spin–orbit coupling in the compounds. Our results provide a ternary platform to study and engineer the electronic properties of transition metal chalcogenides related to large spin–orbit coupling.</jats:p>

<jats:p>The binary pnictide semimetals have attracted considerable attention due to their fantastic physical properties that include topological effects, negative magnetoresistance, Weyl fermions, and large non-saturation magnetoresistance. In this paper, we have successfully grown the high-quality V<jats:sub>1 – <jats:italic>δ</jats:italic> </jats:sub> Sb<jats:sub>2</jats:sub> single crystals by Sb flux method and investigated their electronic transport properties. A large positive magnetoresistance that reaches 477% under a magnetic field of 12 T at <jats:italic>T</jats:italic> = 1.8 K was observed. Notably, the magnetoresistance showed a cusp-like feature at the low magnetic fields and such feature weakened gradually as the temperature increased, which indicated the presence of a weak antilocalization effect (WAL). In addition, based upon the experimental and theoretical band structure calculations, V<jats:sub>1 – <jats:italic>δ</jats:italic> </jats:sub> Sb<jats:sub>2</jats:sub> is a research candidate for a flat band.</jats:p>

<jats:p>High-quality large 1<jats:italic>T</jats:italic> phase of Ti<jats:italic>X</jats:italic> <jats:sub>2</jats:sub> (<jats:italic>X</jats:italic> = Te, Se, and S) single crystals have been grown by chemical vapor transport using iodine as a transport agent. The samples are characterized by compositional and structural analyses, and their properties are investigated by Raman spectroscopy. Several phonon modes have been observed, including the widely reported <jats:italic>A</jats:italic> <jats:sub>1<jats:italic>g</jats:italic> </jats:sub> and <jats:italic>E<jats:sub>g</jats:sub> </jats:italic> modes, the rarely reported <jats:italic>E<jats:sub>u</jats:sub> </jats:italic> mode (∼183 cm<jats:sup>−1</jats:sup> for TiTe<jats:sub>2</jats:sub>, and ∼185 cm<jats:sup>−1</jats:sup> for TiS<jats:sub>2</jats:sub>), and even the unexpected <jats:italic>K</jats:italic> mode (∼85 cm<jats:sup>−1</jats:sup>) of TiTe<jats:sub>2</jats:sub>. Most phonons harden with the decrease of temperature, except that the <jats:italic>K</jats:italic> mode of TiTe<jats:sub>2</jats:sub> and the <jats:italic>E<jats:sub>u</jats:sub> </jats:italic> and “<jats:italic>A</jats:italic> <jats:sub>2<jats:italic>u</jats:italic> </jats:sub>/Sh” modes of TiS<jats:sub>2</jats:sub> soften with the decrease of temperature. In addition, we also found phonon changes in TiSe<jats:sub>2</jats:sub> that may be related to charge density wave phase transition. Our results on Ti<jats:italic>X</jats:italic> <jats:sub>2</jats:sub> phonons will help to understand their charge density wave and superconductivity.</jats:p>

<jats:p>Two-dimensional (2D) layered perovskites have emerged as potential alternates to traditional three-dimensional (3D) analogs to solve the stability issue of perovskite solar cells. In recent years, many efforts have been spent on manipulating the interlayer organic spacing cation to improve the photovoltaic properties of Dion–Jacobson (DJ) perovskites. In this work, a serious of cycloalkane (CA) molecules were selected as the organic spacing cation in 2D DJ perovskites, which can widely manipulate the optoelectronic properties of the DJ perovskites. The underlying relationship between the CA interlayer molecules and the crystal structures, thermodynamic stabilities, and electronic properties of 58 DJ perovskites has been investigated by using automatic high-throughput workflow cooperated with density-functional (DFT) calculations. We found that these CA-based DJ perovskites are all thermodynamic stable. The sizes of the cycloalkane molecules can influence the degree of inorganic framework distortion and further tune the bandgaps with a wide range of 0.9–2.1 eV. These findings indicate the cycloalkane molecules are suitable as spacing cation in 2D DJ perovskites and provide a useful guidance in designing novel 2D DJ perovskites for optoelectronic applications.</jats:p>

<jats:p>Non-Abelian anyons can emerge as fractionalized excitations in two-dimensional systems with topological order. One important example is the Moore–Read fractional quantum Hall state. Its quasihole states are zero-energy eigenstates of a parent Hamiltonian, but its quasiparticle states are not. Both of them can be modeled on an equal footing using the bipartite composite fermion method. We study the entanglement spectrum of the cases with two or four non-Abelian anyons. The counting of levels in the entanglement spectrum can be understood using the edge theory of the Moore–Read state, which reflects the topological order of the system. It is shown that the fusion results of two non-Abelian anyons is determined by their distributions in the bipartite construction.</jats:p>