Spatial distribution of the maximum Josephson current in superconducting tunnel junctions

The distribution of the maximum Josephson current in two-dimensional tunnel junctions is investigated both theoretically and experimentally. Measurements of the Josephson current density are performed using low-temperature scanning electron microscopy. Josephson current densities are calculated by means of a numerical iteration procedure, which is presented in detail. These theoretical calculations are found to be essential for the correct interpretation of the measured Josephson current densities. Combining these experimental and theoretical methods, we investigate trapped transverse vortices. Further, the strength of the elementary pinning centers acting upon the trapped flux quanta is measured by recording the shift of the vortex position as a function of an applied Lorentz force. Ringlike vortices are also observed, and the influence of different current feed configurations on the Josephson current distribution is investigated.