Many-body effects in silicene, silicane, germanene and germanane.

Silicene, which is the silicon equivalent of carbon-based graphene and shares some of the unique properties with graphene, has been attracting more and more attention since its synthesis and represents a breakthrough in current silicon-based technology. In this work, many-body effects in silicene, silicane, germanene and germanane have been demonstrated based on the Green's function perturbation theory, i.e., GW + Bethe-Salpeter equation. Due to confinement, many-body effects play a pivotal role in quasi-particle excitations and optical absorption spectra, which leads to excitonic resonance (π→π* excitation) in silicene and germanene, and strongly bound excitons in silicane and germanane with considerable binding energies.