Proximity superconductivity in ballistic graphene at high magnetic fields

ORAL

Abstract

We present measurements of the superconducting proximity effect in graphene-based Josephson junctions with a mean free path of several microns, which exceeds the junctions' length [1]. The junctions exhibit low contact resistance and large supercurrents. We observe Fabry-P\'{e}rot oscillations in the normal-state resistance and the critical current of the junctions. The proximity effect is mostly suppressed in magnetic fields of \textless 10 mT showing the conventional Fraunhofer interference pattern; however, unexpectedly, a weak proximity effect survives in magnetic fields as high as 1 T. Superconducting states randomly appear and disappear as a function of field and carrier concentration, and each exhibits a supercurrent carrying capacity close to the universal limit of e$\Delta $/h where $\Delta $ is the superconducting gap of the contacts. We attribute the high-field supercurrent to mesoscopic Andreev states that persist near graphene edges. Our work reveals new proximity regimes that can be controlled by quantum confinement and cyclotron motion. [1] Ben Shalom et al., arXiv:1504.03286 (2015)

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Authors

  • Jonathan Prance

    • Department of Physics, University of Lancaster, Lancaster, UK
    • Lancaster University
    • University of Lancaster, UK

  • M. Ben Shalom

    • School of Physics and Astronomy, University of Manchester, Oxford Road, M13 9PL Manchester, UK

  • M. J. Zhu

    • School of Physics and Astronomy, University of Manchester, Oxford Road, M13 9PL Manchester, UK

  • V. I. Fal’ko

    • School of Physics and Astronomy, University of Manchester, Oxford Road, M13 9PL Manchester, UK

  • A. Mishchenko

    • School of Physics and Astronomy, University of Manchester, Oxford Road, M13 9PL Manchester, UK

  • A. V. Kretinin

    • School of Physics and Astronomy, University of Manchester, Oxford Road, M13 9PL Manchester, UK

  • K. S. Novoselov

    • School of Physics and Astronomy, University of Manchester, Oxford Road, M13 9PL Manchester, UK

  • C. R. Woods

    • School of Physics and Astronomy, University of Manchester, Oxford Road, M13 9PL Manchester, UK

  • K. Watanabe

    • National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044 Japan

  • T. Taniguchi

    • National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044 Japan

  • A. K. Geim

    • School of Physics and Astronomy, University of Manchester, Oxford Road, M13 9PL Manchester, UK