High-buckled 3×3 stanene with a topologically nontrivial energy gap

We demonstrate an efficient way of tuning the atomic buckling in stanene to open a topologically nontrivial energy gap. Via tuning the growth kinetics, we obtain an unexpected high-buckled √3×√3 stanene on the Bi(111) substrate. Scanning tunneling microscopy (STM) study combined with density functional theory (DFT) calculation confirms that the √3×√3 stanene is a distorted 1×1 structure with a high-buckled Sn in every three 1×1 unit cells. The high-buckled √3×√3 stanene favors a large band inversion at the Γ point, and the spin-orbit coupling (SOC) opens a topologically nontrivial energy gap. This study provides an alternate way to tune the topology of monolayer topological materials.