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Project Summary: The presence of a Weyl semimetal state in the spin-aligned phase of intrinsic antiferromagnetic topological
Insulator MnBi2Te4 (MBT) makes them intriguing candidates for higher Chern numbers (C). Most existing research on the n = 0 Landau Level (LL) has focused on the C = 1 Chern insulator state. However, limited research efforts have been made to understand the quantum states associated with higher C, and the nature and origin of the states leading to these plateaus remain unresolved. Recently, by fabricating high-quality MBT devices with mobility exceeding 6000 cm2/Vs, the Wang group at UCLA demonstrated that the C = 2 state strongly relies on the exchange coupling (Js), consistent with the theoretical models based on the coupled Dirac cone tight binding model. This C = 2 Chern state is distinct from the conventional filling factor v = 2 state originating from the band LLs, as the latter does not depend on the exchange coupling. Moreover, they also observed the breaking of LL degeneracy, leading to the appearance of odd and even sequences that vary with magnetic fields and are strongly correlated with Js. These findings highlight the significance of the exchange coupling in understanding the behavior of Chern states and LLs in magnetic quantum systems.
Publication: Su Kong Chong et al., Phys. Rev. Lett. 132, 146601 (2024). Cover Image. DOI: 10.1103/PhysRevLett.132.146601
2DCC Role:This research resulted from a close collaboration between 2DCC and Prof. Wang. The 2DCCâs unique ability of growing high-quality MnBi2Te4 single crystals made this impactful work possible