Strong many-body effects in silicene-based structures

Abstract

Silicene, which is the silicon equivalent of carbon-based graphene and shares some unique properties with graphene, has been attracting more and more attention since its successful synthesis. Using Green's function perturbation theory, many-body effects in silicene, hydrogenated silicene (silicane), fluorinated silicene (fluorosilicene), as well as armchair silicene nanoribbons (ASiNRs) are studied. Optical resonances in silicene have been aroused by excitonic effects: The $\ensuremath{\pi}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{*}$ excitonic resonance at 1.23 eV is contributed by the characteristic dispersion of Dirac fermions, while the one at 3.75 eV is due to the $\ensuremath{\sigma}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{*}$ transition. Hydrogenation or fluorination of silicene removes the conductivity at the Dirac point and causes band-gap opening. In addition to the remarkable self-energy effects, optical absorption properties of silicane, fluorosilicene, and ASiNRs are dominated by strong excitonic effects with formation of bound excitons with considerable binding energies.