Development of a Nanocluster-Graphene Proximity Device

The study of metal clusters has revealed quantum nanoscale effects unique to the fully size-resolved regime. A highly notable example is electronic shell structure, akin to that in atoms and nuclei, which arises when confined conduction electrons organize into discrete energy levels. One consequence is the possibility of dramatic enhancement in electron Cooper pairing. Recent research from our group has provided evidence of this enhancement in certain free Al clusters, with the electronic transition taking place at a temperature two orders of magnitude above that of bulk aluminum. We now aim to take advantage of this phenomenon by exploring the pairing transition in size-selected nanoclusters soft-landed on an appropriate substrate. For example, a network of such superconducting nanoislands will induce superconductivity in graphene even at low coverages. Theory predicts that an array of clusters will not only support, but even enhance the Josephson current by 2-3 orders of magnitude. We will report on our progress toward the fabrication and characterization of a graphene-nanocluster device for displaying enhanced superconducting transport.