Observation of Restored Topological Surface States in Magnetically Doped Topological Insulator

Jinsu Kim,Miyoung Kim,Myung-Hwa Jung,Kyuwook Ihm,Manoj K Sharma,Kyung-Tae Ko,Otgonbayar Dugerjav,Jae-Hoon Park,Hanchul Kim,Eun-Ha Shin,Chanyong Hwang,Hwangho Lee

doi:10.1038/s41598-018-37663-8

Abstract

The introduction of ferromagnetic order in topological insulators in general breaks the time-reversal symmetry and a gap is opened in topological surface bands. Various studies have focused on gap-opened magnetic topological insulators, because such modified band structures provide a promising platform for observing exotic quantum physics. However, the role of antiferromagnetic order in topological insulators is still controversial. In this report, we demonstrate that it is possible to restore the topological surface states by effectively reducing the antiferromagnetic ordering in Gd-substituted Bi2Te3. We successfully control the magnetic impurities via thermal treatments in ultra-high vacuum condition and observe apparent restoration of topological surface band dispersions. The microscopic mechanism of atomic rearrangements and the restoration process of topological surface states are unraveled by the combination of scanning tunneling microscopy measurements and density functional theory calculations. This work provides an effective way to control the magnetic impurities which is strongly correlated with topological surface states.

Highlights

Were observed near the magnetic phase transition at xc = 0.09 from paramagnetic (PM) to antiferromagnetic (AFM) phase[18]
We have successfully controlled the magnetic impurity populations by thermal treatments in ultra-high vacuum (UHV) condition, and have observed the improvement of 2D TSS characteristics such as large linear magnetoresistance, Shubnikov-de Haas (SdH) oscillations with 1/2 offset, and multiband Hall behavior. These results are clearly explained by the restoration of TSS band dispersion, which is detected in angle-resolved photoemission spectroscopy (ARPES) measurements
The detailed dynamics of the TSS restoration are discussed with the combination of scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations

Summary

Introduction

We expect the non-trivial topological features after annealing, as observed at xc in the previous work[18], so that we check this scenario by measuring the magneto-transport properties such as the magnetoresistance (MR) ratio and Hall resistivity ρxy. For the c-annealed sample, the MR curve in Fig. 2c shows SdH oscillations at high magnetic fields.

Results

Conclusion