Lifetime and surface-to-bulk scattering off vacancies of the topological surface state in the three-dimensional strong topological insulators Bi2Te3 and Bi2Se3

TL;DR

This paper investigates the lifetimes of topological surface states in Bi2Te3 and Bi2Se3, revealing how elastic scattering off vacancies affects electron coherence and how surface-to-bulk and surface-to-surface scattering contributions vary with energy.

Contribution

It provides a detailed analysis of elastic scattering mechanisms, including the impact of defect resonances, on the lifetimes of topological surface electrons in these materials.

Findings

Surface-to-bulk scattering dominates when many bulk states are available.

Defect resonances significantly alter surface state lifetimes.

Lifetimes range from tens of femtoseconds to picoseconds at 1% defect concentration.

Abstract

We analyze the finite lifetimes of the topologically protected electrons in the surface state of Bi2Te3 and Bi2Se3 due to elastic scattering off surface vacancies and as a function of energy. The scattering rates are decomposed into surface-to-surface and surface-to-bulk contributions, giving us new fundamental insights into the scattering properties of the topological surface states (TSS). If the number of possible final bulk states is much larger than the number of final surface states, then the surface-to-bulk contribution is of importance, otherwise the surface-to-surface contribution dominates. Additionally, we find defect resonances that have a significant impact on the scattering properties of the TSS. They can strongly change the lifetime of the surface state to vary between tens of fs to ps at surface defect concentrations of 1 at%.