Dichotomy of Thermodynamic and Transport Properties in Twisted Double-Bilayer Graphene

ORAL

Abstract

The emergence of controlled, two-dimensional moiré materials has uncovered a new platform for investigating topological physics. Twisted double bilayer graphene has been predicted to host a topologically non-trivial gapped phase with Chern number equal to two at charge neutrality, when half the flat bands are filled. However, it can be difficult to diagnose topological states using a single measurement. The challenge lies in probing the bulk and edge properties at the same time. A combination of chemical potential measurements, transport measurements, and theoretical calculations provides insight to the band topology of twisted double bilayer graphene. The thermodynamic gap extracted from chemical potential measurements shows that twisted double bilayer graphene is a bulk insulator under an applied transverse electric field, while transport measurements show metallic edge transport. A Landauer-Büttiker analysis of measurements on multi-terminal samples allows us to quantitatively assess edge state scattering. We interpret these results as signatures of the predicted topological phase at charge neutrality.

*The work at The University of Texas was supported by the National Science Foundation Grant MRSEC DMR-1720595, and Army Research Office under Grant No. W911NF-17-1-0312. The work at Princeton University was supported by the Office of Naval Research under Grant No. N00014-20-1-2303.

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Publication: Bulk and Edge Properties of Twisted Double-Bilayer Graphene. Nat. Phys. -- in press. Preprint at http://arxiv.org/abs/2101.03621 (2021).

Presenters

  • Yimeng Wang

    • The University of Texas at Austin

Authors

  • Yimeng Wang

    • The University of Texas at Austin

  • Jonah Herzog-Arbeitman

    • Princeton University

  • G W Burg

    • University of Texas at Austin

  • Jihang Zhu

    • Max Planck Institute for the Physics of Complex Systems

  • Kenji Watanabe

    • NIMS
    • Research Center for Functional Materials, National Institute for Materials Science
    • National Institute of Materials Science
    • National Institue for Materials Science
    • National Institute for Materials Science, Japan
    • National Institute for Materials Science (NIMS)
    • National Institute of Materials Science, Tsukuba, Japan
    • National Institute for Materials Science
    • NIMS, Japan

  • Takashi Taniguchi

    • National Institute for Materials Science, Tsukuba, Japan
    • National Institute for Materials Science
    • NIMS
    • Kyoto Univ
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Ibaraki 305-0044, Japan.
    • 3 National Institute for Materials Science, Tsukuba, Japan
    • National Institute for Materials Science; 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
    • National Institute of Materials Science, Tsukuba, Japan
    • National Institute of Materials Science
    • Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
    • National Institute for Materials Science (Japan)
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
    • Kyoto University
    • International Center for Materials Nanoarchitectonics
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Japan
    • International Center for Materials Nanoarchitectonics, National Institute for MaterialsScience, 1-1 Namiki, Tsukuba 305-0044, Japan
    • National Institute for Material Science, Japan
    • National Institute for Material Science
    • National Institute of Material Sciences, Japan
    • NIMS, Tsukuba
    • 2National Institute for Materials Science, Namiki 1-1, Ibaraki 305-0044, Japan.
    • National Institute of Materials Science, Tsukuba, Ibaraki 305-0044, Japan
    • National Institute for Materials Science, Japan
    • International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki Tsukuba, Ibaraki 305-0044, Japan.
    • NIMS, Japan
    • National Institute for Materials Science (NIMS)
    • NIMS. Japan
    • International Center for Material Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
    • International Center for Material Nanoarchitectonics, National Institute for Materials Science
    • National Institute for Materials Science Tsukuba
    • National Institute for Materials Science, 1-1 Namiki
    • National Institute for Materials Science of Japan
    • National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
    • NIMS - National Institute for Material Science, Japan
    • International Center for Materials Nanoarchitectonics, National Institute for Material Science, Tsukuba, Ibaraki 305-0044, Japan.
    • National Institute for Material Science, Tsukuba
    • National Institute for Materials Science, International Center for Materials Nanoarchitectonics
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
    • National Institute of Material Science
    • National Institute for Materials Science,1-1 Namiki, Tsukuba, 305-0044, Japan

  • Allan H MacDonald

    • University of Texas at Austin

  • Andrei B Bernevig

    • Princeton University

  • Emanuel Tutuc

    • University of Texas at Austin