Type-I and Type-II Superconductivity in Wide Josephson Junctions

Abstract

The magnetic field dependence of the maximum dc Josephson current ${I}_{max}$ of wide $\mathrm{P}\mathrm{b}\ensuremath{-}{\mathrm{PbO}}_{x}\ensuremath{-}\mathrm{P}\mathrm{b}$ Josephson junctions, for which the junction length $L$ was about 10 times the Josephson penetration depth ${\ensuremath{\lambda}}_{J}$, has been measured. The experimental data are in excellent agreement with a theoretical prediction by Owen and Scalapino, who have numerically calculated ${I}_{max}$ versus ${H}_{e}$ for a Josephson junction with $L=10{\ensuremath{\lambda}}_{J}$, and who have also shown that the Meissner region and the vortex structure are reflected in the ${I}_{max}$ versus-${H}_{e}$ curve in a very characteristic way. It is shown that the boundary conditions of Owen and Scalapino's model can be most conveniently fulfilled with a crosstype junction configuration, and that the ${\mathrm{PbO}}_{x}$ tunneling barrier layers were fairly uniform.