Tunneling between Superconductors in the Vortex State

Superconductor-insulator-superconductor ($S-I-S$) and $S_1-I-S_2$ tunnel junctions have been studied with the thin-film electrodes in a dilute vortex state, at temperatures such that the tunneling is predominantly due to the vortex-core excitations. We conclude that the vortex cores in the upper film lie on top of those in the lower film, but that the net tunneling transition probability between vortex-core states is very much smaller than usual tunneling probabilities.