2. Josephson effect; Josephson junction model

The Josephson junction consists of a thin insulating barrier separating two superconductors. As long as the applied current I does not exceed a critical current I _c , the Cooper pairs can tunnel through the insulating barrier without developing a voltage across it. The macroscopic wave function undergoes, across the junction, a phase difference θ given by (first Josephson relation):

By interrupting a superconducting ring with one or two Josephson junctions, it is possible to visualize a radio-frequency...