Metacinnabar ({\beta}-HgS): a strong 3D topological insulator with highly anisotropic surface states

TL;DR

This paper demonstrates that metacinnabar ({eta}-HgS) is a highly anisotropic 3D topological insulator with unique surface states, identified through density-functional calculations showing a near-flat Dirac cone and strong surface anisotropy.

Contribution

It reveals the topologically protected surface states of HgS and characterizes their extreme anisotropy, highlighting the role of surface symmetry breaking.

Findings

Presence of topologically protected edge states on HgS surface

Dirac cone is highly anisotropic with large velocity in one direction

Surface symmetry breaking causes extreme anisotropy in surface states

Abstract

We establish the presence of topologically protected edge states on the (001) surface of HgS in the zinc-blende structure using density-functional electronic structure calculations. The Dirac point of the edge state cone is very close to the bulk valence band maximum. The Dirac cone is extremely anisotropic with a very large electron velocity along one diagonal of the surface elementary cell x' and a nearly flat dispersion in the perpendicular direction y'. The strong anisotropy originates from a broken fourfold rotoinversion symmetry at the surface.