Electronic structure and quasiparticle bandgap of silicene structures

We report first-principles results on the electronic structure of silicene. For planar and simply buckled silicenes, we confirm their zero-gap nature and show a significant renormalization of their Fermi velocity by including many-electron effects. However, the other two recently proposed silicene structures exhibit a finite bandgap, indicating that they are gapped semiconductors instead of expected Dirac-fermion semimetals. This finite bandgap is preserved with the Ag substrate included. Moreover, our GW calculation reveals enhanced many-electron effects in these two-dimensional structures. Finally, the bandgap of the latter two structures can be tuned in a wide range by applying strain.