title: Ballistic Josephson junctions in edge-contacted graphene.
abstract: Hybrid graphene-superconductor devices have attracted much attention since the early days of graphene research. So far, these studies have been limited to the case of diffusive transport through graphene with poorly defined and modest-quality graphene/superconductor interfaces, usually combined with small critical magnetic fields of the superconducting electrodes. Here, we report graphene-based Josephson junctions with one-dimensional edge contacts of molybdenum rhenium. The contacts exhibit a well-defined, transparent interface to the graphene, have a critical magnetic field of 8 T at 4 K, and the graphene has a high quality due to its encapsulation in hexagonal boron nitride. This allows us to study and exploit graphene Josephson junctions in a new regime, characterized by ballistic transport. We find that the critical current oscillates with the carrier density due to phase-coherent interference of the electrons and holes that carry the supercurrent caused by the formation of a Fabry-Pérot cavity. Furthermore, relatively large supercurrents are observed over unprecedented long distances of up to 1.5 μm. Finally, in the quantum Hall regime we observe broken symmetry states while the contacts remain superconducting. These achievements open up new avenues to exploit the Dirac nature of graphene in interaction with the superconducting state.
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, Delft, GA 2600, The Netherlands.
authors.forename: V E
authors.initials: VE
authors.lastname: Calado
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, Delft, GA 2600, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Goswami
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, Delft, GA 2600, The Netherlands.
authors.forename: G
authors.initials: G
authors.lastname: Nanda
authors.affiliation: Instituut-Lorentz, Universiteit Leiden, PO Box 9506, Leiden, RA 2300, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Diez
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, Delft, GA 2600, The Netherlands.
authors.forename: A R
authors.initials: AR
authors.lastname: Akhmerov
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: K
authors.identifier: http://orcid.org/0000-0003-3701-8119
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, Delft, GA 2600, The Netherlands.|Laboratory for Quantum Limited Devices, Physics Department, Moscow State Pedagogical University, 29 Malaya Pirogovskaya St., Moscow 119992, Russia.
authors.forename: T M
authors.initials: TM
authors.lastname: Klapwijk
authors.affiliation: Kavli Institute of Nanoscience, Delft University of Technology, Delft, GA 2600, The Netherlands.
authors.forename: L M K
authors.initials: LM
authors.lastname: Vandersypen