Density of states and magnetoconductance of disordered Au point contacts

We report low-temperature magnetotransport measurements on electrochemically fabricated atomic scale gold nanojunctions. As $\overrightarrow{T}0,$ the junctions exhibit nonperturbatively large zero bias anomalies (ZBA’s) in their differential conductance. We consider several explanations and find that the ZBA’s are consistent with a reduced local density of states in the disordered metal. We suggest that this is a result of Coulomb interactions in a granular metal with moderate intergrain coupling. Magnetoconductance of atomic scale junctions also differs significantly from that of less geometrically constrained devices, and supports this explanation.