Enhanced Superconductivity in Spin-Orbit Proximitized Bernal Bilayer Graphene

ORAL

Abstract

In the presence of a large electric field, Bernal bilayer graphene (BLG) features several broken-symmetry phases and magnetic-field-induced superconductivity with a critical temperature T≈ 30 mK. Here, we show that placing monolayer tungsten diselenide (WSe2) on BLG promotes Cooper pairing in several ways: superconductivity appears at zero magnetic field, exhibits an order of magnitude enhancement in Tc, and occurs over a wide density range. By mapping quantum oscillations, we establish that superconductivity emerges from a polarized normal state, with two out of four spin-valley flavors predominantly populated. For BLG-WSe2 with moderate Ising spin-orbit coupling, in-plane magnetic field measurements reveal that the critical field roughly obeys the Pauli limit on one end of the superconducting dome yet sharply violates on the other. Moreover, the superconductivity arises only for electric fields that push BLG hole wavefunctions towards WSe2—suggesting that proximity-induced Ising spin-orbit coupling plays a key role in stabilizing the pairing. These results provide an essential step towards engineering robust, highly tunable, and ultra-clean graphene-based superconductors.

*This work has been primarily supported by NSF-CAREER award (DMR-1753306), and Office of Naval Research (grant no. N142112635), and Army Research Office under Grant Award W911NF17-1-0323. Nanofabrication efforts have been in part supported by Department of Energy DOE-QIS program (DE-SC0019166). S.N-P. acknowledges support from the Sloan Foundation (grant no. FG-2020-13716). J.A. and S.N.-P. also acknowledge support of the Institute for Quantum Information and Matter, an NSF Physics Frontiers Center with support of the Gordon and Betty Moore Foundation through Grant GBMF1250.

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Publication: Spin-Orbit Enhanced Superconductivity in Bernal Bilayer Graphene, arXiv:2205.05087

Presenters

  • Yiran Zhang

    • California Institute of Technology

Authors

  • Yiran Zhang

    • California Institute of Technology

  • Robert M Polski

    • Caltech

  • Alex R Thomson

    • Caltech

  • Etienne Lantagne-Hurtubise

    • California Institute of Technology
    • Caltech

  • Cyprian K Lewandowski

    • Florida State University

  • Haoxin Zhou

    • Department of Applied Physics and Material Science, California Institute of Technology; Department of Physics, University of California at Santa Barbara
    • California Institute of Technology

  • 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

  • Jason F Alicea

    • Caltech
    • California Institute of Technology

  • Stevan Nadj-Perge

    • Caltech