We have investigated several classes of strong spin-orbit chalcogenides related to the (Pb,Sn)Te series studied in connection with the Dirac fermion physics in the 1980s. Our first-principle theoretical calculations suggest that ternary chalcogenides TlBiX2 and TlSbX2 (X=Te, Se, S) series harbor small bandgap topological insulators with single Dirac cone on some selective surfaces whereas the isostructural and isoelectronic silver-based AgBiX2 and AgSbX2 (X=Te, Se, S) series do not. We find that several Tl-compounds are in the vicinity of a topological critical point. We identify the precise surface termination that realizes the single Dirac cone. The single-Dirac-cone surface is shown to be correlated with a termination that minimizes dangling bonding effects favorable for ARPES experiments. Our results further suggest that this class of topological semi-metals may harbor odd-parity topological superconductors similar to the possibility proposed for CuxBi2Se3 (T_c ~ 4K).
@article{arxiv.1003.2615,
title = {Single-Dirac-Cone topological surface states on pseudo-IV-VI-semimetal/semiconductors: Thallium-based III-V-VI2 Ternary Chalcogenides},
author = {H. Lin and R. S. Markiewicz and L. A. Wray and L. Fu and M. Z. Hasan and A. Bansil},
journal= {arXiv preprint arXiv:1003.2615},
year = {2010}
}