First-Principles Calculations of van der Waals and Spin Orbit Effects on the Two-Dimensional Topological Insulator Stanene and Stanene on Ge(111) Substrate

摘要

The structural and electronic properties of the monolayer and bilayer stanene structures have been studied using first-principles calculations. For the monolayer, the buckled structure is more stable than the flat one, with an opening of the band gap when spin-orbit coupling is taken into account, as mentioned in recent studies. For the bilayer, three types of stacking are considered: parallel layers, anti-parallel layers, and parallel layers where the first layer is shifted from the second one. These three configurations are named AA1, AA2, and AB, respectively. The two layers are separated by the distance d. The interactions between two layers of stanene are strong for a short distance, while the van der Waals bonding appears for a longer distance. Furthermore, stanene was fabricated experimentally on a substrate; thus, we proposed another study of electronic properties of stanene deposited on Ge(111) to reveal other behavior as a topological insulator and show the existence of the quantum spin Hall effect.