Abstract

Graphene’s band structure and established device fabrication methods make it an ideal starting point for investigating Dirac physics in a range of materials, notably the surface states of bulk topological insulators. A better understanding of phenomena related to the Dirac cone is required, particularly in devices with superconducting contacts.

In graphene driven superconducting by the proximity effect, zero energy modes are predicted in vortex cores. To explore whether the presence of such modes can be detected solely through charge transport, we have fabricated Josephson junction arrays on graphene. We find that the mean conductance and universal conductance fluctuations are enhanced below the critical temperature and field of the superconductor, with greater enhancement away from the graphene Dirac point. We also observe features in the magnetoconductance at rational fractions of flux quanta per array unit cell, which we attribute to the formation of vortices in the arrays.