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MnBi₂Te₄, an intrinsic magnetic topological insulator, has recently been predicted to possess a variety of topological quantum states, including quantum anomalous Hall insulator, axion insulator in its 2D thin layers and an ideal Weyl semimetal state in its bulk ferromagnetic (FM) phase^1,2. Although several interesting properties, including Chern insulator, axion insulator, and anomalous Hall effect (AHE) in its canted antiferromagnetic phase have been observed, the predicted FM Weyl state remains elusive^3-5. In this talk, we will report our magnetotransport studies on MnSb_xBi_2-xTe₄. We will show when the Sb concentration is tuned to be close to a critical concentration where carrier density reaches a minimum, the FM phase under a high field range exhibits a large intrinsic AHE with the anomalous Hall angle reaching 5%. Moreover, the carrier mobility also reaches a maximum at the critical concentration. All these features are possibly associated with the long-sought ideal Weyl state.

¹D. Zhang et al., Phys. Rev. Lett. 122, 206401 (2019)
²J. Li et al., Sci. Adv. 5, eaaw5685 (2019)
³Y. Deng et al., arXiv:1904.11468
⁴C. Liu et al., arXiv:1905.00715
⁵S. H. Lee et al., Phys. Rev. Research 1, 012011 (2019)