Double Fe-impurity charge state in the topological insulator Bi$_2$Se$_3$

TL;DR

This study investigates how individual Fe impurities affect the electronic properties of the topological insulator Bi$_2$Se$_3$, revealing that impurity charge states depend on their location, local environment, and doping level, with implications for electron scattering.

Contribution

It demonstrates the ability to remotely charge Fe impurities using STM and explains how impurity charge states vary with local conditions and Fermi level positioning.

Findings

Impurity charge states depend on their crystallographic position.

Local environment influences impurity charging behavior.

Impurity effects are significant for electron scattering in topological insulators.

Abstract

The influence of individual impurities of Fe on the electronic properties of topological insulator Bi$_2$Se$_3$ is studied by Scanning Tunneling Microscopy. The microscope tip is used in order to remotely charge/discharge Fe impurities. The charging process is shown to depend on the impurity location in the crystallographic unit cell, on the presence of other Fe impurities in the close vicinity, as well as on the overall doping level of the crystal. We present a qualitative explanation of the observed phenomena in terms of tip-induced local band bending. Our observations evidence that the specific impurity neighborhood and the position of the Fermi energy with respect to the Dirac point and bulk bands have both to be taken into account when considering the electron scattering on the disorder in topological insulators.