Restoration of Topological Surface State by Vacuum Annealing in Magnetically Doped Topological Insulator

TL;DR

This study demonstrates that vacuum annealing can restore the topological surface state in magnetically doped topological insulators, reversing surface gap effects caused by magnetic order.

Contribution

It introduces a novel method of using ultra-high vacuum annealing to recover topological surface states in magnetic topological insulators.

Findings

Surface state gap closes after annealing.

Typical topological surface state features reappear.

Atomic migration mechanism elucidated by microscopy and theory.

Abstract

The introduction of magnetic order on the surface of topological insulators in general breaks the two-dimensional character of topological surface state (TSS). Once the TSS disappears, it is improbable to restore the topological surface properties. In this report, we demonstrate that it is possible to restore the inherent TSS by ultra-high vacuum annealing. Starting from an antiferromagnetic Gd-doped Bi2Te3, that has surface state gap without TSS properties, after annealing we observed the gap closing as well as typical TSS features in physical properties. The microscopic mechanism of atomic migration and TSS restoration by annealing process is unraveled by the combination of scanning tunneling microscopy measurements and density functional theory calculations. This approach to control the surface of topological insulators and stabilize the TSS simply by vacuum annealing provides a new platform towards the exploitation of their topological properties.