Figure 1: Band-bending-induced surface electronic structure of Bi2Se3.
From: Emergent quantum confinement at topological insulator surfaces
(a) A near-surface electrostatic potential variation causes downward band bending of both the conduction band minimum (CBM) and valence band (VB) edges, forming a surface quantum well. It shifts the Dirac point of the TSS (yellow band) further below the Fermi level and causes the conduction band states to be restructured into ladders of Rashba-split two-dimensional subbands, En (red bands), with envelope wave functions (dark red) peaked close to the surface. A schematic spin texture of these states is shown by the arrows. The finite valence band width provides simultaneous confinement of the valence band states, causing these to also become quantized into ladders of M-shaped states, En′(blue bands). These features can all be seen in ARPES measurements of the surface electronic structure (b) and are well described by the surface projection (that is, real-space projection onto the first three quintuple layers) of an ab initio-derived tight-binding model (c) of the ideal Bi2Se3 bulk structure subject only to a perturbing electrostatic potential close to the surface (false colour scale inset). k| is along the Γ–M direction.
