Spatial and energy distribution of topological edge states in single Bi(111) bilayer

By combining scanning tunneling microscopy and spectroscopy, angle-resolved photoemission spectroscopy, and density functional theory band calculations, we directly observe and resolve the one-dimensional edge states of single bilayer (BL) Bi(111) islands on clean Bi2Te3 and Bi(111)-covered Bi2Te3 substrates. The edge states are localized in the vicinity of step edges having an ~2 nm wide spatial distribution in real space and reside in the energy gap of the Bi(111) BL. Our results demonstrate the existence of nontrivial topological edge states of single Bi(111) bilayer as a two-dimensional topological insulator.