Scattering properties of the three-dimensional topological insulator Sb2Te3: Coexistence of topologically trivial and non-trivial surface states with opposite spin-momentum helicity

摘要

The binary chalcogenides Bi2Te3 and Bi2Se3 are the most widely studiedtopological insulators. Although the quantum anomalous Hall effect has recentlybeen observed in magnetically doped Sb2Te3 this compound has been studied to amuch lesser extend. Here, by using energy resolved quasiparticle interferencemapping, we investigate the scattering events of pristine Sb2Te3 surfaces. Wefind that, in addition to the Dirac fermions, another strongly spin polarizedsurface resonance emerges at higher energies in the unoccupied electronicstates. Although the two surface states are of different origin, i.e.topologically protected and trivial, respectively, both show stronglydirectional scattering properties and absence of backscattering. Comparisonwith ab-initio calculations demonstrates that this is a direct consequence oftheir spin momentum locked spin texture which is found to exhibit an oppositerotational sense for the trivial state and the Dirac state.