An isolated Dirac cone on the surface of ternary tetradymite-like topological insulators

We have extended the search for topological insulators to the ternary tetradymite-like compounds M₂X₂Y (M = Bi or Sb; X and Y = S, Se or Te), which are variations of the well-known binary compounds Bi ₂Se₃ and Bi₂Te3. Our first-principles computations suggest that five existing compounds are strong topological insulators with a single Dirac cone on the surface. In particular, stoichiometric Bi₂Se2S, Sb₂Te₂Se and Sb ₂Te₂S are predicted to have an isolated Dirac cone on their naturally cleaved surface. This finding paves the way for the realization of the topological transport regime.