Quantum spin Hall effect and emergence of conducting edge states in silicene supported by MX (M=Ga, In; X=S, Se, Te) monolayer.

The electronic structure of silicene supported by monolayer of different monochalcogenide MX (GaS, GaSe, GaTe and InSe) substrates has been investigated by first principle density functional theory. By calculating the formation energies and phonons, it has been seen that silicene supported by monolayer of MX remains stable. The systems retain their almost 2 D planner configurations with small buckling as that of the free standing silicene and also the Bader charge analysis shows that silicene hardly interacts with any of the MX substrates. The Dirac cone with a small gap (∼ 3 0 – 5 0   meV) has been observed in each of the cases. All the systems show quantum spin Hall effect and the quantum spin Hall conductivities have been estimated to be within the range ∼ 2 − 5 ℏ e S/cm, which are larger than that of the free standing silicene. Our calculations show that even if the systems have bulk band gaps but the edge states are conducting in nature. [ABSTRACT FROM AUTHOR]