Terahertz electromagnetic response and its electric field manipulation of bulked silicene

Abstract

We theoretically investigate the infrared optical properties of a three-terminal silicene-based device under the irradiation of a circularly polarized terahertz (THz) electromagnetic field, utilizing the intersubband transition theorem at low temperatures. It has been demonstrated that the electronic structure of bulked silicene can be tuned to the topological insulated (TI) and band insulated (BI) state, respectively, via the back-gate voltage induced staggered sublattice potential. Furthermore, with the enhancement of the staggered sublattice potential, the refractive index, extinction coefficient and optical conductivity from the TI state spin-up and -down subbands are observed to be red-and blue-shifted, respectively, while those from the BI state spin-up and -down subbands are proved to be continually blue-shifted. The collective excitations and individual electron-hole pair excitations induced a TI and BI state electron energy loss spectrum (EELS) with a similar red-and/or blue-shift behaviour as the refractive index, extinction coefficient and optical conductivity. The obtained results may be useful in the design of the spintronic and optoelectronic devices based on silicene.

Infrared to ultraviolet optical response for armchair-edge silicene nanoribbons

“…One notes that all the observed optical transitions for metallic 11-ASiNR come from the different indexed valence and conduction subbands, [31] while the A / M and A / C absorptions of the semiconducting 9-and 10-ASiNRs should owe to the same indexed subbands. It seems that the semiconducting 9-/10-ASiNRs are more sensitive to external electromagnetic field [33,34,36] than metallic 11-ASiNR within the infrared to visible energy range.…”

“…According to the intersubband-transition theorem [33,34,36] for semiconductors, the imaginary dielectric function e 2 ðxÞ for N-ASiNR irradiated by an external electromagnetic field with photon energy hx (as denoted by the wave arrows in Fig. 1) can be expressed as…”

“…Furthermore, the real part of the dielectric function can be calculated from the Kramers-Krönig relation [33,34,36] as…”

“…The surface differential optical spectra of a complete self-assembled Si nanoribbon layer on silver have been experimentally [32] demonstrated to be much different from those of a silicene monolayer. The width-dependent electronic structure and optical response for ASiNRs make it more attractive in future silicene-based nanoscale optoelectronic devices, [33][34][35][36]; we address these significant issues in the present work.…”

“…1) at low temperatures are demonstrated from the dipole-transition theorem [33][34][35][36] for semiconductors. The dipole transitions [38,39] from the valence subbands to the smaller indexed conduction ones for 9-, 10-, and 11-ASiNRs have been found to increase continually, while those to the larger indexed conduction subbands increase firstly and then decrease.…”