Engineering electronic structure of a 2D topological insulator Bi(111) bilayer on Sb nanofilms by quantum confinement effect

摘要

We report on fabrication of a two-dimensional topological insulator-Bi(111)bilayer on Sb nanofilms via a sequential molecular beam epitaxy (MBE) growthtechnique. Our angle-resolved photoemission measurements demonstrate theevolution of the electronic band structure of the heterostructure as a functionof the film thickness and reveal the existence of a two-dimensional spinfulmassless electron gas within the top Bi bilayer. Interestingly, Ourfirst-principles calculation extrapolating the observed band structure showsthat, by tuning down the thickness of the supporting Sb films into the quantumdimension regime, a pair of isolated topological edge states emerges in apartial energy gap at 0.32 eV above the Fermi level as a consequence of quantumconfinement effect. Our results and methodology of fabricating nanoscaleheterostructures establish the Bi bilayer/Sb heterostructure as a platform ofgreat potential for both ultralow-energy-cost electronics and surface-basedspintronics.