Spectroscopy measurements of superconductor-graphene-normal metal junctions

ORAL

Abstract

We discuss results on single layer graphene junctions made by a graphene sheet in contact with a superconducting tunnel probe and a normal ohmic contact. The superconducting gap of the tunnel probes is well formed at 250 mK. However, we observe an additional conductance gap at smaller biases (a ``subgap'' feature), which is symmetric in bias voltage and oscillates as function of the applied backgate voltage. Even though no supercurrent flow is observed, due to the large spacing of the leads, the observed effects may be due to Andreev bound states. We discuss the possible role of Andreev bound states in determining the inner subgap features of the conductance, and potential spectroscopic signatures arising from the ballistic transport of normal electrons in graphene that travel between the superconducting and the normal contacts.

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Authors

  • Travis Dirks

    University of Illinois at Urbana-Champaign

  • Yung-Fu Chen

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin-Madison

  • Cesar Chialvo

    University of Illinois at Urbana-Champaign, Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign

  • B. Uchoa

    University of Illinois at Urbana-Champaign, University of Illinois

  • Taylor Hughes

    University of Illinois at Urbana-Champaign

  • Siddhartha Lal

    University of Illinois at Urbana-Champaign, University of Illinois, Dept. of Physics, University of Illinois

  • Paul Goldbart

    University of Illinois at Urbana-Champaign, Universiy of Illinois, University of Illinois, UIUC, Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign

  • Nadya Mason

    University of Illinois at Urbana-Champaign, Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, University of Illinois Urbana-Champaign