Superconducting via contacts to graphene

ORAL

Abstract

Highly transparent superconducting contacts is of great interest to research exploring the superconducting proximity effect in two-dimensional materials. In prior studies on NbSe2/graphene heterostructures [Li et al, Phys. Rev. B 101, 195405 (2020)], Andreev reflections with efficiencies of 80% were demonstrated. This work suggests that a clean van der Waals interface facilitates the superconducting proximity coupling. Here we report on the fabrication and performance of superconducting NbN contacts to graphene, realized through transferred via contacts. The NbN via contacts are sputtered into etched pits of a h-BN sheet, and then transferred to graphene to form a van der Waals-like interface. Our NbN films have a superconducting transition temperature of Tc ~7 K, and an upper critical field of Hc2 > 9 T at 2K. Differential conductance measurements on NbN/graphene junctions show enhancement at small DC voltage biases, as a result of Andreev reflection occurring at the NbN/graphene interface. We characterize the performance of junctions fabricated using different processes. The large Hc2 of NbN will facilitate the studies of the superconducting proximity effect in the quantum Hall regime.

*Penn State MRSEC for Nanoscale Science (DMR-2011839)

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Presenters

  • Cequn Li

    • Pennsylvania State University

Authors

  • Cequn Li

    • Pennsylvania State University

  • Ke Huang

    • Pennsylvania State 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

  • Jun Zhu

    • Pennsylvania State University