Time-reversal-protected single-Dirac-cone topological-insulator states in Bi2Te3 and Sb2Te3: Topologically Spin-polarized Dirac fermions with pi Berry's Phase
We show that the strongly spin-orbit coupled materials Bi2Te3 and Sb2Te3
(first non-Bi topological insulator) and their derivatives belong to the Z2
(Time-Reversal-Protected, elastic backscattering suppressed)
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 (about 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 surface spin-only
Dirac fermions can be controlled through systematic Mn doping, making these
materials classes potentially suitable for exploring novel topological physics.
We emphasize (theoretically and experimentally) that the Dirac node is well
within the bulk-gap and not degenerate with the bulk valence band