Intrinsic magnetic topological insulators: MnBi₂Te₄and beyond

Intrinsic magnetic topological insulators are novel states of quantum matter possessing both inherent magnetic order and topological electronic states, which offer a fertile playground to explore emergent quantum physics. The antiferromagnetic topological insulator MnBi₂Te₄ [1-4] is a rapidly rising star in the research field. The material is theoretically predicted to host rich topological quantum states (e.g., topological axion states, magnetic Weyl semimetal, and quantum anomalous Hall (QAH) effect). In addition to theoretical proposals, I will also introduce recent experimental findings, including the discoveries of antiferromagnetic topological insulator states [1,4], QAH effect [5], robust axion insulator and Chern insulator phases [6], high-Chern-number and high-temperature QAH effect [7], helical Chern insulator phase [8], etc. An outlook for future work will be given. Importantly, the working temperature of MnBi₂Te₄ is limited by its rather weak ferromagnetic exchange, making superior material candidates desirable. In this perspective, I will briefly report an unexpected theoretical finding of room-temperature ferromagnetism and large-gap QAH insulators in lithium-decorated iron-based superconductor materials LiFeX (X=S, Se, Te) [9], which is awaiting for experimental proof.
Reference:
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[5] Y. Deng, et al. Science, eaax8156 (2020).
[6] C. Liu, et al. Nature Mater. (2020).
[7] J. Ge, et al. arXiv:1907.09947.
[8] C. Liu, et al. arXiv:2001.08401.
[9] Y. Li, et al. arXiv:1912.07461.