Theoretical prediction of topological insulators in thallium-based III-V-VI₂ ternary chalcogenides

¹  Bremen Center for Computational Materials Science, Universität Bremen - Am Fallturm 1, 28359 Bremen, Germany, EU
²  Physikalisches Institut (EP3) and Institute for Theoretical Physics and Astrophysics, University of Würzburg 97074 Würzburg, Germany, EU
³  Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences Beijing 100190, China
⁴  Department of Physics, McCullough Building, Stanford University - Stanford, CA 94305-4045, USA
⁵  Microsoft Research, Station Q, Elings Hall, University of California - Santa Barbara, CA 93106, USA

Received: 15 April 2010
Accepted: 26 April 2010

Abstract

We predict a new class of three-dimensional topological insulators in thallium-based III-V-VI₂ ternary chalcogenides, including lBiQ₂ and TlSbQ₂ (Q = Te, Se and S). These topological insulators have robust and simple surface states consisting of a single Dirac cone at the Γ point. The mechanism for topological insulating behavior is elucidated using both first-principle calculations and effective field theory models. Remarkably, one topological insulator in this class, TlBiTe₂, is also a superconductor when doped with p-type carriers. We discuss the possibility that this material could be a topological superconductor. Another material, TlSbS₂, is on the border between topological insulator and trivial insulator phases, in which a topological phase transition can be driven by pressure.