# Robust axion insulator and Chern insulator phases in a two-dimensional antiferromagnetic topological insulator

## Abstract

The intricate interplay between non-trivial topology and magnetism in two-dimensional materials can lead to the emergence of interesting phenomena such as the quantum anomalous Hall effect. Here we investigate the quantum transport of both bulk crystal and exfoliated MnBi2Te4 flakes in a field-effect transistor geometry. For the six septuple-layer device tuned into the insulating regime, we observe a large longitudinal resistance and zero Hall plateau, which are characteristics of an axion insulator state. The robust axion insulator state occurs in zero magnetic field, over a wide magnetic-field range and at relatively high temperatures. Moreover, a moderate magnetic field drives a quantum phase transition from the axion insulator phase to a Chern insulator phase with zero longitudinal resistance and quantized Hall resistance h/e2, where h is Planck’s constant and e is electron charge. Our results pave the way for using even-number septuple-layer MnBi2Te4 to realize the quantized topological magnetoelectric effect and axion electrodynamics in condensed matter systems.

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## Data availability

All raw and derived data used to support the findings of this work are available from the authors on request.

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## Acknowledgements

We thank W. Duan, S. Fan, X. Feng, Z. Hao, L. Yang and S. Ye for helpful discussions and technical supports. This work is supported by the Basic Science Centre Project of NSFC (grant no. 51788104), the National Key R&D Program of China (grant nos. 2018YFA0307100, 2017YFA0302900 and 2018YFA0305603), MOST of China (grant no. 2015CB921000) and Natural Science Foundation of China (grant nos. 51991343 and 21975140). This work is also partially supported by the Beijing Advanced Innovation Centre for Future Chip (ICFC).

## Author information

Y.Y.W., J.S.Z., Y.X. and K.H. proposed the research and Y.Y.W. supervised. C.L. and Y.X.L. carried out the transport measurements. Y.C.W. fabricated and characterized the devices. H.L. and Y.W. grew the MnBi2Te4 bulk crystals. Y.X. and J.H.L. performed first-principles calculations. Y.Y.W., J.S.Z., Y.X. and C.L. prepared the manuscript with comments from all authors.

Correspondence to Yong Xu or Jinsong Zhang or Yayu Wang.

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### Competing interests

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## Supplementary information

### Supplementary Information

Supplementary Figs. 1–5 and discussions.

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Liu, C., Wang, Y., Li, H. et al. Robust axion insulator and Chern insulator phases in a two-dimensional antiferromagnetic topological insulator. Nat. Mater. (2020). https://doi.org/10.1038/s41563-019-0573-3

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• Published:

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