Engineering topological surface-states: HgS, HgSe and HgTe

TL;DR

This study uses density functional calculations to explore how surface termination and modifications affect the topological surface-states of HgS, HgSe, and HgTe, revealing the importance of surface chemistry on Dirac cone properties.

Contribution

It provides detailed insights into how surface passivation and modifications influence the topological surface-states and Dirac cone anisotropy in HgX materials.

Findings

Dirac cone is isotropic on (110) surface but anisotropic on (001) surface.

Surface passivation modifies Dirac cone anisotropy due to dangling bonds.

Surface modifications change the spatial location and decay length of protected edge-states.

Abstract

Using density functional electronic structure calculations, we establish the consequences of surface termination and modification on protected surface-states of metacinnabar (beta-HgS). Whereas we find that the Dirac cone is isotropic and well-separated from the valence band for the (110) surface, it is highly anisotropic at the pure (001) surface. We demonstrate that the anisotropy is modified by surface passivation because the topological surface-states include contributions from dangling bonds. Such dangling bonds exist on all pure surfaces within the whole class HgX with X = S, Se, or Te and directly affect the properties of the Dirac cone. Surface modifications also alter the spatial location (depth and decay length) of the topologically protected edge-states which renders them essential for the interpretation of photoemission data.