Electric-field-diversified optical properties of bilayer silicene

The rich optical properties of AA-bottom-top (bt) bilayer silicene (BS) in a uniform perpendicular electric field (E) are investigated through the use of the tight-binding model. The distinctive multivalley band structure presents a semimetallic behavior but with a sizeable intraband gap. The main features of the energy dispersion appear in the optical absorption spectrum through transitions between band-edge states obeying specific selection rules. The E field clearly modifies the energy dispersion, especially opening a band gap, leading to a substantial influence on the optical properties. This field creates additional excitation channels and increases the frequency and intensity of the spectral structures. The inclusion of electron-hole interaction gives rise to a slight difference in the spectral intensity and strongly affects the fluctuation in the threshold intensity as the field strength is varied. The interplay between the special lattice structure, atomic interactions, electron-hole interaction, and a E field robustly diversifies the absorption spectra.