Figure 2: Confinement of the electronic states.
From: Emergent quantum confinement at topological insulator surfaces

(a,b) show the depth-dependence of the carrier density, n(z), and potential profile, V(z), near the surface of Bi2Se3, respectively. The blue shading schematically represents the spatial extent of the surface-localized 2DEG. (c) Quintuple-layer (QL) projected supercell calculations of the electronic structure along Γ–M, revealing the varying spatial confinement of the different electronic states (false colour scale shown to right).