Ab initio studies of adatom- and vacancy-induced band bending in Bi2Se3

Förster T, Krüger P, Rohlfing M

Abstract

We investigate the influence of potassium adsorption and selenium vacancies in the surface layer on the electronic properties of the prototypical topological insulator Bi2Se3. These modifications of the surface give rise to oscillations in the charge density that extend deep into the crystal. They result in a long-ranged potential perpendicular to the surface (also referred to as band bending) and new states in the band structure that are reminiscent of the states of a two-dimensional electron gas. Very similar effects have been observed in several experiments. The reorganization of the charge deep inside the crystal as a reaction to the surface modification constitutes a remarkable property of Bi2Se3 and is closely related to its layered structure. The emergence of the long-ranged potential as a direct consequence of the charge reorganization turns out to be a generic property of \BiSe. However, calculations without spin-orbit coupling show that the band bending is not related to the nontrivial topological character of Bi2Se3.