Abstract
We investigate hopping transport in granular superconductors in the weak-coupling insulating regime and find that it is governed by the interplay between the granule charging energy and the single granule superconducting gap . At , the transport is mediated by single electron hopping, while at , the transport is dominated by hopping of Cooper pairs. We show that in the former case and at low temperatures, , superconducting pairing suppresses inelastic cotunneling processes, giving rise to giant negative magnetoresistance. We find the range of intermediate temperatures where transport is dominated by inelastic cotunneling but having an activation temperature behavior; this regime is specific to granular superconductors. We investigate different conductivity regimes and construct a transport phase diagram.
- Received 18 October 2006
DOI:https://doi.org/10.1103/PhysRevB.75.092201
©2007 American Physical Society