Topological magnetoelectric response in ferromagnetic axion insulators

Yuhao Wan; Jiayu Li; Qihang Liu

doi:10.1093/nsr/nwac138

Topological magnetoelectric response in ferromagnetic axion insulators

Natl Sci Rev. 2022 Jul 22;11(2):nwac138. doi: 10.1093/nsr/nwac138. eCollection 2024 Feb.

Authors

Yuhao Wan¹, Jiayu Li¹, Qihang Liu^{1

2

3}

Affiliations

¹ Department of Physics and Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, China.
² Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, China.
³ Guangdong Provincial Key Laboratory for Computational Science and Material Design, Southern University of Science and Technology, Shenzhen 518055, China.

Abstract

The topological magnetoelectric effect (TME) is a hallmark response of the topological field theory, which provides a paradigm shift in the study of emergent topological phenomena. However, its direct observation is yet to be realized due to the demanding magnetic configuration required to gap all surface states. Here, we theoretically propose that axion insulators with a simple ferromagnetic configuration, such as the MnBi₂Te₄/(Bi₂Te₃)_n family, provide an ideal playground to realize the TME. In the designed triangular prism geometry, all the surface states are magnetically gapped. Under a vertical electric field, the surface Hall currents give rise to a nearly half-quantized orbital moment, accompanied by a gapless chiral hinge mode circulating in parallel. Thus, the orbital magnetization from the two topological origins can be easily distinguished by reversing the electric field. Our work paves the way for direct observation of the TME in realistic axion-insulator materials.

Keywords: axion insulator; magnetic topological materials; topological magnetoelectric effect.