Te-Vacancy-Induced Surface Collapse and Reconstruction in Antiferromagnetic Topological Insulator MnBi2Te4

Fuchen Hou; Qiushi Yao; Chun-Sheng Zhou; Xiao-Ming Ma; Mengjiao Han; Yu-Jie Hao; Xuefeng Wu; Yu Zhang; Hongyi Sun; Chang Liu; Yue Zhao; Qihang Liu; Junhao Lin

doi:10.1021/acsnano.0c03149

Te-Vacancy-Induced Surface Collapse and Reconstruction in Antiferromagnetic Topological Insulator MnBi₂Te₄

ACS Nano. 2020 Sep 22;14(9):11262-11272. doi: 10.1021/acsnano.0c03149. Epub 2020 Aug 27.

Authors

Fuchen Hou^{1

2}, Qiushi Yao¹, Chun-Sheng Zhou¹, Xiao-Ming Ma¹, Mengjiao Han^{1

2}, Yu-Jie Hao¹, Xuefeng Wu¹, Yu Zhang^{1

3}, Hongyi Sun¹, Chang Liu^{1

4}, Yue Zhao^{1

4}, Qihang Liu^{1

4

5

2}, Junhao Lin^{1

2}

Affiliations

¹ Department of Physics, Southern University of Science and Technology, Shenzhen 518055, Guangdong, P. R. China.
² Shenzhen Key Laboratory of for Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, China.
³ Department of Physics, University of Hong Kong, Hong Kong, P. R. China.
⁴ Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, P. R. China.
⁵ Guangdong Provincial Key Laboratory for Computational Science and Material Design, Southern University of Science and Technology, Shenzhen 518055, China.

PMID: 32813492
DOI: 10.1021/acsnano.0c03149

Abstract

MnBi₂Te₄ is an antiferromagnetic topological insulator that has stimulated intense interest due to its exotic quantum phenomena and promising device applications. The surface structure is a determinant factor to understand the magnetic and topological behavior of MnBi₂Te₄, yet its precise atomic structure remains elusive. Here we discovered a surface collapse and reconstruction of few-layer MnBi₂Te₄ exfoliated under delicate protection. Instead of the ideal septuple-layer structure in the bulk, the collapsed surface is shown to reconstruct as a Mn-doped Bi₂Te₃ quintuple layer and a Mn_xBi_yTe double layer with a clear van der Waals gap in between. Combined with first-principles calculations, such surface collapse is attributed to the abundant intrinsic Mn-Bi antisite defects and the tellurium vacancy in the exfoliated surface, which is further supported by in situ annealing and electron irradiation experiments. Our results shed light on the understanding of the intricate surface-bulk correspondence of MnBi₂Te₄ and provide an insightful perspective on the surface-related quantum measurements in MnBi₂Te₄ few-layer devices.

Keywords: MnBi2Te4; antisite defects; in situ surface dynamics; magnetic topological insulator; surface reconstruction; tellurium vacancy.