Well-localized edge states in two-dimensional topological insulators: ultrathin Bi films

TL;DR

This paper investigates the localization properties of edge states in 2D topological insulators, showing that ultrathin Bi films host well-localized edge states with a broad momentum-space dispersion, contrasting with other systems like HgTe quantum wells.

Contribution

It provides a theoretical analysis of edge state localization in 2D topological insulators, highlighting Bi(111) ultrathin films as having particularly well-localized edge states.

Findings

Edge states in Bi(111) ultrathin films extend over almost the entire Brillouin zone.

The momentum-space width of edge-state dispersion scales inversely with penetration depth.

Bi(111) bilayer system exhibits well-localized edge states unlike HgTe quantum wells.

Abstract

We theoretically study the generic behavior of the penetration depth of the edge states in two-dimensional quantum spin Hall systems. We found that the momentum-space width of the edge-state dispersion scales with the inverse of the penetration depth. As an example of well-localized edge states, we take the Bi(111) ultrathin film. Its edge states are found to extend almost over the whole Brillouin zone. Correspondingly, the bismuth (111) 1-bilayer system is proposed to have well-localized edge states in contrast to the HgTe quantum well.