NUCLEATION, PINNING, AND FLOW OF VORTICES IN JOSEPHSON-JUNCTION ARRAYS WITH DEFECTS

We numerically study the properties of two-dimensional overdamped Jose phson-junction arrays containing defects. We employ fast algorithms ad apted to arrays with defects. In arrays as large as 128 x 256, we inve stigate the vortex pinning regime, the transition from the superconduc ting to the resistive state and various finite size effects. Owing to the highly anisotropic nature of the pinning potential in rectangular arrays, we observe pinned vortices in arrays much smaller than expecte d so far. The energy of the array changes discontinuously at transitio ns, cross vortex sectors thar are characterized by the number of pinne d vortices. These pinned vortices also cause hysteresis in the array w hich we investigate in some detail. The periodic regime reveals the na ture of waves which carry the vortices. Finally, an analysis of extend ed and distributed defect patterns affirms the analogy of current driv en arrays with hydrodynamic flows.