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

The magnetic field dependence of the maximum dc Josephson current Iₘₐₓ of wide Pb-PbOₓ-Pb Josephson junctions, for which the junction length L was about 10 times the Josephson penetration depth λJ, has been measured. The experimental data are in excellent agreement with a theoretical prediction by Owen and Scalapino, who have numerically calculated Iₘₐₓ versus Hₑ for a Josephson junction with L=10λJ, and who have also shown that the Meissner region and the vortex structure are reflected in the Iₘₐₓ versus-Hₑ 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 PbOₓ tunneling barrier layers were fairly uniform.