Spatial Distribution of Topological Surface State Electrons in Bi$_2$Te$_3$ Probed by Low Energy Na$^+$ Ion Scattering

TL;DR

This study uses low energy Na+ ion scattering to directly probe the spatial distribution of topological surface state electrons in Bi2Te3, revealing dipole-induced inhomogeneities linked to the surface electronic structure.

Contribution

It introduces a novel application of alkali ion scattering to experimentally map the electron distribution in topological surface states of Bi2Te3.

Findings

Larger neutralization from Te sites indicates an upward dipole.

Smaller neutralization from Bi sites indicates a downward dipole.

Method provides direct evidence of electron spatial distribution in surface states.

Abstract

Bi$_2$Te$_3$ is a topological insulator whose unique properties result from topological surface states in the band gap. The neutralization of scattered low energy Na$^+$, which is sensitive to dipoles that induce inhomogeneities in the local surface potential, is larger when scattered from Te than from Bi, indicating an upwards dipole at the Te sites and a downwards dipole above Bi. These dipoles are caused by the spatial distribution of the conductive electrons in the topological surface states. This result demonstrates how this alkali ion scattering method can be applied to provide direct experimental evidence of the spatial distribution of electrons in filled surface states.