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.
@article{arxiv.1105.0501,
title = {Metacinnabar ({\beta}-HgS): a strong 3D topological insulator with highly anisotropic surface states},
author = {Franccois Virot and Roland Hayn and Manuel Richter and Jeroen van den Brink},
journal= {arXiv preprint arXiv:1105.0501},
year = {2012}
}