Photoemission Spectroscopy of Magnetic and Non-magnetic Impurities on the Surface of the Bi$_2$Se$_3$ Topological Insulator

TL;DR

This study uses photoemission spectroscopy to investigate how magnetic and non-magnetic impurities affect the surface states of Bi$_2$Se$_3$, revealing their surprising robustness at low impurity levels and the influence of hexagonal warping at higher doping.

Contribution

It provides new insights into the impurity effects on topological insulator surface states, showing their resilience and the role of warping in scattering processes.

Findings

Surface states are insensitive to impurities at low concentrations.

Hexagonal warping enables scattering regardless of magnetic properties.

Impurities influence scattering mainly at high doping levels.

Abstract

Dirac-like surface states on surfaces of topological insulators have a chiral spin structure that suppresses back-scattering and protects the coherence of these states in the presence of non-magnetic scatterers. In contrast, magnetic scatterers should open the back- scattering channel via the spin-flip processes and degrade the state's coherence. We present angle-resolved photoemission spectroscopy studies of the electronic structure and the scattering rates upon adsorption of various magnetic and non-magnetic impurities on the surface of Bi$_2$Se$_3$, a model topological insulator. We reveal a remarkable insensitivity of the topological surface state to both non-magnetic and magnetic impurities in the low impurity concentration regime. Scattering channels open up with the emergence of hexagonal warping in the high-doping regime, irrespective of the impurity's magnetic moment.