Effect of Disorder on the Vortex Dynamics in Superconducting Josephson Junction Arrays and Clusters.

We have studied the effect of intrinsic disorder on the transport properties of large Josephson junction arrays and clusters. In large arrays, intrinsic random disorder results in the washing out of features in the magnetoresistance. It also gives rise to multiple onsets in the resistive transition as a function of temperature. Large arrays are difficult to model because of the large number of junctions involved, thus we have studied the effect of local (single junction) disorder in smaller arrays referred to as clusters. The transport measurements on clusters indicate that features due to disorder in the junction critical currents, dominate the properties. We have developed a simple model in real space to understand the static vortex configurations and the motion of the vortices.