Exchange Biased Anomalous Hall Effect in Chern Insulators

ORAL

Abstract

A central theme in condensed matter physics is the interplay between magnetism and topology, which gives rise to many exciting quantum phenomena, including the quantum anomalous Hall (QAH) state and axion insulator state. Over the past five years, the intrinsic antiferromagnetic (AFM) topological insulator (TI) MnBi2Te4 has attracted much attention, primarily due to the realization of the QAH and axion insulator states in odd and even number layers, respectively. However, the existence of native defects in MnBi2Te4, such as Mn/Bi antisites and Te vacancies, has greatly hindered the realization of these two phenomena. In this work, based on the manually exfoliated MnBi2Te4 thin flakes, we fabricated a series of MnBi2Te4 devices with the thickness of 5 septuple layers (SLs) to 8SLs. We first demonstrated the presence of the Chern insulator state under high magnetic field (> 6T). We observed a large negative exchange bias effect in odd-number layer devices, while this effect is absent in the even-layer samples. Our theoretical calculations suggest that the layer-dependent exchange biased anomalous Hall effect is a result of the formation of the surface reconstruction in MnBi2Te4, particularly near zero magnetic field.

*This work is supported by the ARO Award (W911NF2210159), the NSF grant (DMR-2241327), and the Gordon and Betty Moore Foundation's EPiQS Initiative (GBMF9063 to C. -Z. C.)

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Presenters

  • Bo Chen

    • Pennsylvania State University

Authors

  • Bo Chen

    • Pennsylvania State University

  • Xiaoda Liu

    • Pennsylvania State University

  • Yuhang Li

    • University of California, Riverside

  • Han Tay

    • Pennsylvania State University

  • Takashi Taniguchi

    • Kyoto Univ
    • National Institute for Materials Science
    • Research Center for Materials Nanoarchitectonics
    • Research Center for Materials Nanoarchitectonics, National Institute for Materials Science
    • National Institute for Materials Sciences
    • NIMS
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
    • National Institute for Material Science
    • International Center for Materials Nanoarchitectonics, NIMS, Japan
    • International Center for Materials Nanoarchitectonics, Tsukuba
    • National Institue for Materials Science
    • Kyoto University
    • National Institute of Materials Science
    • International Center for Materials Nanoarchitectonics and National Institute for Materials Science

  • Kenji Watanabe

    • National Institute for Materials Science
    • NIMS
    • Research Center for Electronic and Optical Materials, National Institute for Materials Science
    • Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
    • National Institute for Material Science

  • Moses H Chan

    • Pennsylvania State University

  • Jiaqiang Yan

    • Oak Ridge National Laboratory

  • Fengqi Song

    • Nanjing Univ

  • Ran Cheng

    • UC Riverside

  • Cui-Zu Chang

    • Pennsylvania State University
    • The Pennsylvania State University