Quantum impurity in the bulk of topological insulator

TL;DR

This paper studies how an Anderson impurity behaves inside a topological insulator's bulk, revealing unique Kondo and bound state phenomena depending on the band structure, with implications for electron correlation effects.

Contribution

It introduces a detailed analysis of impurity states in the bulk of topological insulators, highlighting differences from surface impurities and exploring the effects of band inversion.

Findings

Simultaneous Kondo peak and in-gap bound states in band-inverted insulators.

Broader mixed-valence regime in band-inverted case.

Potential self-screening of the Kondo effect due to impurity-bound state interactions.

Abstract

We investigate physical properties of an Anderson impurity embedded in the bulk of a topological insulator. The slave-boson mean-field approximation is used to account for the strong electron correlation at the impurity. Different from the results of a quantum impurity on the surface of a topological insulator, we find for the band-inverted case, a Kondo resonant peak and in-gap bound states can be produced simultaneously. However, only one type of them appears for the normal case. It is shown that the mixed-valence regime is much broader in the band-inverted case, while it shrinks to a very narrow regime in the normal case. Furthermore, a self-screening of the Kondo effect may appear when the interaction between the bound-state spin and impurity spin is taken into account.