Enhancement and deterioration of the critical current by defects in Josephson-junction arrays

We study how the addition of defects in an otherwise uniform Josehpson junction array modifies the critical current of the array, by numerically solving the system of coupled Josephson equations. Our results confirm the existence of two different regimes, depending on the normalized maximum Josephson current of each junction, $i_{\rm max}$: for large $i_{\rm max}$, the defects deteriorate partially the critical state of the uniform array and so decrease the critical current, while for low values of $i_{\rm max}$, the defects help the formation of the critical state, which leads to an enhancement of critical current. The results are discussed in comparison with the behavior of type-II superconductors, for which the inclusion of defects always results in an enhancement of the critical current.