Kinetic Inductance and Flat-Band Superconductivity in Magic-Angle Twisted Bilayer Graphene Probed by cQED

ORAL

Abstract

The physics of superconductivity in magic-angle twisted bilayer graphene (MATBG) is a topic of keen interest in moiré systems research, and it may provide insight into the pairing mechanism of other strongly correlated materials such as high-TCsuperconductors.

We use DC-transport and microwave circuit quantum electrodynamics (cQED) techniques to measure the superfluid stiffness of superconducting MATBG via its kinetic inductance. We find the superfluid stiffness to be much larger than expected from conventional single-band Fermi liquid theory; rather, it aligns well with theory involving quantum geometric effects that are dominant at the magic angle.

The temperature dependence of the superfluid stiffness exhibits a power-law behavior, which contraindicates an isotropic BCS model; instead, the extracted power-law exponents indicate an anisotropic superconducting gap, whether interpreted using the BCS Fermi liquid model or a quantum geometric theory of flat-band superconductivity. Taken together, these findings strongly suggest a connection between quantum geometry, superfluid stiffness, and unconventional superconductivity in MATBG. The combined DC-microwave measurement platform used here is applicable to the investigation of other atomically thin superconductors.

*This research was funded in part by the US Army Research Office grant no. W911NF-2210023, in part by the National Science Foundation QII-TAQS grant no. OMA-1936263, in part by the Air Force Office of Scientific Research under award number FA2386-21-1-4058, and in part under Air Force Contract No. FA8702-15-D-0001. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the US Government.

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Presenters

  • Joel I-Jan Wang

    • Massachusetts Institute of Technology

Authors

  • Joel I-Jan Wang

    • Massachusetts Institute of Technology

  • Miuko Tanaka

    • Univ of Tokyo
    • Institute for Solid State Physics, The University of Tokyo, Kashiwa

  • Thao H Dinh

    • Harvard University

  • Daniel Rodan-Legrain

    • Massachusetts Institute of Technology

  • Sameia Zaman

    • Massachusetts Institute of Technology

  • Max Hays

    • MIT
    • Massachusetts Institute of Technology (MIT)
    • Massachusetts Institute of Technology

  • Bharath Kannan

    • Atlantic Quantum

  • Aziza Almanakly

    • Massachusetts Institute of Technology

  • David K Kim

    • MIT Lincoln Lab
    • Lincoln Laboratory, Massachusetts Institute of Technology

  • Bethany M Niedzielski

    • MIT Lincoln Laboratory
    • Lincoln Laboratory, Massachusetts Institute of Technology

  • Kyle Serniak

    • MIT Lincoln Laboratory
    • Lincoln Laboratory, Massachusetts Institute of Technology

  • Mollie E Schwartz

    • MIT Lincoln Laboratory
    • Lincoln Laboratory, Massachusetts Institute of Technology

  • Kenji Watanabe

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

  • Takashi Taniguchi

    • National Institute for Materials Science
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science
    • Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
    • International Center for Materials Nanoarchitectonics, National Institute of Material Science, Tsukuba, Japan
    • Advanced Materials Laboratory, National Institute for Materials Science

  • Jeffrey A Grover

    • Massachusetts Institute of Technology (MIT)
    • Massachusetts Institute of Technology
    • MIT

  • Terry P Orlando

    • Massachusetts Institute of Technology

  • Simon Gustavsson

    • Massachusetts Institute of Technology

  • Pablo Jarillo-Herrero

    • Massachusetts Institute of Technology

  • William D Oliver

    • Massachusetts Institute of Technology
    • Massachusetts Institute of Technology (MIT)