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

The magnetic field dependence of the maximum dc Josephson current $I_{max}$ of wide $\mathrm{P}\mathrm{b}-{\mathrm{PbO}}_x-\mathrm{P}\mathrm{b}$ Josephson junctions, for which the junction length $L$ was about 10 times the Josephson penetration depth ${\lambda }_J$, 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 $L=10\mathrm{}{\lambda }_J$, 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.