THE SUPERCONDUCTING TRANSITION OF 2-D JOSEPHSON-JUNCTION ARRAYS IN A SMALL PERPENDICULAR MAGNETIC-FIELD

We have investigated in detail the influence of a small perpendicular field on the observation of the superconducting phase transition of Josephson-tunnel junction arrays with linear and nonlinear resistance measurements. We find that even a small residual field strongly enhances the crossing of single vortices. In the linear resistance these single-vortex processes dominate over the pairunbinding effects just above and below the Kosterlitz-Thouless temperature. Also, through single-vortex processes, the jump in the nonlinear resistance exponent can be washed out in a field, depending on the cell size and the array width. © 1990 Plenum Publishing Corporation.