Quasi-particle scattering and protected nature of topological states in a parent topological insulator Bi$_2$Se$_3$

TL;DR

This study uses angle-resolved photoemission spectroscopy to investigate the scattering and robustness of topological surface states in Bi$_2$Se$_3$, revealing their protection against weak surface perturbations and insights into quasi-particle decay mechanisms.

Contribution

It provides experimental evidence on the scattering behavior and protection of topological states in Bi$_2$Se$_3$, highlighting their resilience to surface adsorbates and decay into bulk states.

Findings

Topological metallic states are unaffected by adsorbed surface atoms.

Quasi-particle decay mainly occurs into bulk electronic states.

Topological states exhibit protection against weak perturbations.

Abstract

We report on angle resolved photoemission spectroscopic studies on a parent topological insulator (TI), Bi$_2$Se$_3$. The line width of the spectral function (inverse of the quasi-particle lifetime) of the topological metallic (TM) states shows an anomalous behavior. This behavior can be reasonably accounted for by assuming decay of the quasi-particles predominantly into bulk electronic states through electron-electron interaction and defect scattering. Studies on aged surfaces reveal that topological metallic states are very much unaffected by the potentials created by adsorbed atoms or molecules on the surface, indicating that topological states could be indeed protected against weak perturbations.