Topological Surface State Evolution in Chemical Etching of Bi₂Se₃

Topological insulators are materials with insulating bulk while maintaining metallic surface states, which are protected by their topological properties against disorder. Bi₂Se₃ is a typical topological insulator characterized by its large bulk band gap and a robust Dirac cone topological surface state with the crossing point inside the bulk gap. Recently, it has been reported that Bi (111) bilayer can form spontaneously on top of Bi₂Se₃ films under surface etching, which in turn alters its electronic band structures. While the electronic structures of Bi₂Se₃ has been well understood both experimentally and theoretically over the past years, the transitional stages under which a pure Bi₂Se₃ evolves into Bi₂-Bi₂Se₃ state still remain unclear. In this talk, the detailed band structure evolution of pristine Bi₂Se₃ sample under surface etching measured by ARPES will be presented, with an emphasis on the topological surface state. Density Functional Theory calculations will be discussed to provide insights into the topological nature of the intermediate stages during the etching process of this material.

Key Words: Bi₂Se₃, ARPES, surface etching