Floating of the topological surface state on top of a thick lead layer: The case of the Pb/Bi₂Se₃ interface

The puzzling question about the floating of the topological surface state on top of a thick Pb layer has now possibly been answered. A photoemission study of the interface made by Pb on Bi2Se3 for different temperatures and adsorbate coverage conditions, allowed us to demonstrate that the evidence reported in the literature can be related to the surface diffusion phenomenon exhibited by the Pb atoms, which leaves the substrate partially uncovered. Comprehensive density functional theory calculations show that despite the specific arrangement of the atoms at the interface, the topological surface state cannot float on top of the adlayer but rather tends to move inward within the substrate.