Epitaxial growth of stanene and antimonene on noble metal and oxidized metal surfaces

Group-IV and group-V monoelement two-dimensional (2D) materials like stanene, antimonene or bismuthene has been theoretically proposed to be quantum spin Hall (QSH) insulator with large energy gaps for room-temperature use. However, to experimentally fabricate such ultra-thin materials with topologically nontrivial properties remains challenging. It requires accurate control over substrate-interface structures at the atomic level. We successfully grown an ultraflat stanene layer with an in-plane s-p band inversion together with a large spin-orbit-coupling-induced topological gap (~ 0.3 eV), which represents a first group-IV ultraflat graphene-like material displaying topological features in experiment. Such an in-plane s-p band inversion results in a nontrivial σ-orbital-derived QSH phase described by the Bernevig-Hughes-Zhang model and this QSH phase is more environmentally stable comparing to those π-orbital-derived QSH phases. We also successfully synthesized an antimonene film on Ag(111) surface showing an extrordinarily large tensile strain and bilayer stanene on an oxidized Cu(110) surface with large anisotropic strain.