Robust topological edge states and superconductivity in few-layer stanene

Abstract Stanene was proposed to be a large-gap quantum spin Hall insulator, yet to date, convincing evidence of topological edge states in stanene remains to be seen, partly due to the fact that the topological property depends on the interplay between substrate, chemical functionalization, and layer thickness. Here we fabricate 1-5 layer high-quality stanene films on the Bi(111) substrate by using hydrogen atoms as surfactants, and demonstrate their strikingly robust nontrivial topology using scanning tunneling microscopy/spectroscopy and first-principles calculations. The observed topological edge states possess a bilateral-penetration depth shorter than 4 nm, allowing the formation of dense and parallel multi-edge-channels. Our calculations further show that surface hydrogenation helps to improve the quality of stanene films, while the Bi substrate endows the films with robust nontrivial topology. These stanene films also exhibit superconductivity, and the coexistence of nontrivial topology and superconductivity renders them distinct potential to become the simplest one-dimensional topological superconductors.