Tunable energy gap and the transitions between the insulating phases in dual-gated hBN/bilayer graphene superlattices at the charge neutrality point

ORAL

Abstract

We report on the transport properties in hexagonal boron nitride (hBN)/bilayer graphene (BLG) moiré superlattice devices with top and bottom gates (dual gate) enabling individual modulation of the electric displacement field and the carrier density. By measuring the temperature and displacement field dependence of the resistivity at the charge neutrality point (CNP), we estimate the energy gap and demonstrate its tuning by the electric field. Even without an electric field, the alignment of BLG with hBN harbors an energy gap of ~1.4 meV in our device. It is found that the temperature dependence of the resistivity at moiré-induced satellite points is insensitive to an electric field, in contrast to that at the CNP. Under a perpendicular magnetic field, transitions between two insulating phases at the CNP are detected. In the phase diagram, there is no signature of a continuously vanishing gap even in the vicinity of the criticality. This result agrees with a scenario of the formation of a microscopic network of the two competing phases at the first-order transition.

*This work was partially supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number 21H01400, NIMS Nanofabrication Platform in Nanotechnology Platform Program Grant Number JPMXP09F22NM50132, and the World Premier International Research Center Initiative on Materials Nanoarchitectonics sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

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Publication: arXiv:2206.05401

Presenters

  • Takuya Iwasaki

    • National Institute for Materials Science

Authors

  • Takuya Iwasaki

    • National Institute for Materials Science

  • Yoshifumi Morita

    • Gunma University

  • Kenji Watanabe

    • National Institute for Materials Science
    • Research Center for Functional Materials, National Institute of Materials Science
    • Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-044, Japan
    • NIMS
    • Research Center for Functional Materials, National Institute for Materials Science
    • National Institute for Materials Science, Japan
    • Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
    • NIMS Japan

  • Takashi Taniguchi

    • National Institute for Materials Science
    • Kyoto Univ
    • International Center for Materials Nanoarchitectonics, National Institute of Materials Science
    • Kyoto University
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-044, Japan
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science
    • National Institute for Materials Science, Japan
    • National Institute For Materials Science
    • NIMS
    • National Institute for Material Science
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
    • NIMS Japan