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

TL;DR

This study investigates the scattering properties of pristine Sb2Te3 surfaces, revealing coexistence of topologically trivial and non-trivial surface states with opposite spin-momentum helicity, both showing directional scattering and suppressed backscattering.

Contribution

It provides the first detailed analysis of scattering events in Sb2Te3, demonstrating the coexistence of trivial and topological surface states with opposite spin textures.

Findings

Both surface states exhibit directional scattering and lack of backscattering.

The trivial and Dirac states have opposite spin-momentum locking.

The spin textures are confirmed by ab-initio calculations.

Abstract

The binary chalcogenides Bi2Te3 and Bi2Se3 are the most widely studied topological insulators. Although the quantum anomalous Hall effect has recently been observed in magnetically doped Sb2Te3 this compound has been studied to a much lesser extend. Here, by using energy resolved quasiparticle interference mapping, we investigate the scattering events of pristine Sb2Te3 surfaces. We find that, in addition to the Dirac fermions, another strongly spin polarized surface resonance emerges at higher energies in the unoccupied electronic states. Although the two surface states are of different origin, i.e. topologically protected and trivial, respectively, both show strongly directional scattering properties and absence of backscattering. Comparison with ab-initio calculations demonstrates that this is a direct consequence of their spin momentum locked spin texture which is found to exhibit an opposite rotational sense for the trivial state and the Dirac state.