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Interband and intraband transition, dynamical polarization and screening of the monolayer and bilayer silicene in low-energy tight-binding model
摘要： We investigate the interband and intraband transitions of the monolayer and AB-stacked bilayer silicene in low-energy tight-binding model under the electric ?eld, where we focus on the dynamical polarization function, screening due to the charged impurity, and the plasmon dispersion. We obtain the logarithmically divergent polarization function within the random-phase-approximation, whose logarithmic singularities correspond to the discontinuities of the ?rst derivative at momentum q ? 2kF in static case and indicates the topological phase transition point between the gapless semimetal and the gapped band insulator. We also obtain the power-law-dependent Friedel oscillation which can be enhanced by increasing the Rashba coupling. The Friedel oscillation contributes to the screened potential of the charged impurity which scale as (cid:2) r(cid:3)1=2 in short distance from the impurity and scale as (cid:2) r(cid:3)1=3 in long distance from the impurity. In single-particle excitation regime with electron–hole continuum, the interband and intraband transitions happen, and the plasmon dispersion starts to damped into the electron–hole pairs due to the nonzero imaginary part of the polarization function. We also observe the linear (weakly damped) plasmon model for the classical bilayer silicene which is similar to the high-energy p-plasmon or the case of conducting substrate which with strong metallic screening. The density dependence of the plasmon dispersion is also clari?ed in this paper. Our results can also be applied to the other low-energy Dirac models or the topological insulators.
关键词： Friedel oscillation,Collective plasmon model,Silicene,Dynamical polarization,Screened potential
更新于2025-09-10 09:29:36
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Electric and optical properties modulations of armchair silicene nanoribbons by transverse electric fields
摘要： Under the influence of the external transverse electric fields, the effective mass and optical properties of armchair-edge silicene nanoribbons (ASiNRs) are investigated using the first-principles based on density functional theory (DFT). The results show that, comparing without the external transverse electric fields, the band gaps decrease monotonously, and the effective masses of the electrons and holes change non-monotonously with the absolute value of the electric fields, respectively. The total density of states (DOS) shows that, under the external electric fields, 9-ASiNR exhibits p-type semiconductor characters. Because of the obvious difference of the imaginary parts between the//x and//y directions, 9-ASiNR shows an optical anisotropy. In//x direction, the peaks of the dielectric function have evident red shift which are all associated with the electrons transition between Si 3p orbit and Si 3p, 3s orbits.
关键词： Electrics field,Optical properties,First-principles,Silicene nanoribbons,Electric properties
更新于2025-09-10 09:29:36
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Oxidation of Epitaxial Silicene on Ag(111)
摘要： The high chemical reactivity of epitaxial silicene on Ag(111) still remains a debated subject in the literature. In particular results on the oxidation of epitaxial silicene and its related lifetime under ambient conditions are controversially discussed. Here, a detailed investigation of the oxygen exposure to epitaxial silicene layers investigated by means of X-ray photoemission and in situ Raman spectroscopy is reported. The results should clearly cease the discussion on the stability of epitaxial silicene against oxygen as it becomes completely oxidized after an exposure to only 100 L of oxygen. Such a small dose sets strict limits for ex situ studies of epitaxial silicene. Besides the formation of silicon oxide also the silver substrate surface oxidizes, suggesting that the silicene layer can hardly protect it, probably owing to the high number of domain boundaries within the silicene layer.
关键词： epitaxial silicene,2D materials,oxidation,in situ Raman spectroscopy,photoemission spectroscopy
更新于2025-09-10 09:29:36
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The electronic and optical properties of armchair germanene nanoribbons
摘要： The electronic and optical properties of armchair germanene nanoribbons (AGeNRs) are studied using the first principles calculations. The band structure, band-gap size, projected density of states (PDOS), and dielectric function of AGeNRs are calculated. Moreover, the variation of these parameters as a function of various ribbon widths is investigated. By increasing the width of ribbons the band-gap size of pristine AGeNRs is decreased according to three different trends. Based on these trends, it is extracted that the AGeNRs can be divided into three categories named as n=3P, n=3P+1, n=3P+2, here n is the number of germanium atoms in the width and P is an integer. Moreover, all these categories are direct band-gap materials and the order of band-gap size is changed as: EG (3P+2) < EG (3P) < EG (3P+1). Due to the direct band-gap size, it can be extracted that all of AGeNR categories are proper for optical applications. Based on the simulation results of this work, it is demonstrated that the AGeNRs are appropriate for optical devices in the range of infrared applications. In addition, the effect of uniaxial tensile and compressive strain on the band-gap size and the dielectric function of AGeNRs is investigated and it is shown that the electronic and optical properties of AGeNRs can be tuned by strain in a wide range.
关键词： electronic and optical properties,silicene,band gap size,graphene,germanene nanoribbons
更新于2025-09-10 09:29:36
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Tuning the Electronic Structure of Hydrogen-Decorated Silicene
摘要： The effects of strain, charge doping, and external electric field on the electronic structure of a free-standing silicene layer decorated by hydrogen atoms are studied by first-principles density functional theory. Various phases, including insulating, metallic, spin-polarized, and half-metallic have been found, depending on these external factors. The most efficient way of switching the system between these phases is charge doping. The character of the energy gap of the H/silicene system can also be modified, and for charged or for strained systems, the originally indirect gap can be tuned to become direct. The obtained results are very promising in view of the silicene functionalization and potential applications of silicene in the fields of spintronics and optoelectronics.
关键词： density functional theory (DFT),silicene,functionalization
更新于2025-09-04 15:30:14