Observation of Time-Reversal-Protected Single-Dirac-Cone Topological-Insulator States in Bi₂Te₃ and Sb₂Te₃

We show that the strongly spin-orbit coupled materials Bi₂Te₃ and Sb₂Te₃ and their derivatives belong to the Z₂ topological-insulator class. Using a combination of first-principles theoretical calculations and photoemission spectroscopy, we directly show that Bi₂Te₃ is a large spin-orbit-induced indirect bulk band gap (δ∼150  meV) semiconductor whose surface is characterized by a single topological spin-Dirac cone. The electronic structure of self-doped Sb₂Te₃ exhibits similar Z₂ topological properties. We demonstrate that the dynamics of spin-Dirac fermions can be controlled through systematic Mn doping, making these materials classes potentially suitable for topological device applications.