CURRENT STEPS INDUCED BY VORTEX MOTION IN LONG JOSEPHSON TUNNEL-JUNCTIONS

Current-voltage characteristics of a long Josephson tunnel junction in a flux-flow state are studied theoretically as well as experimentally. A general analysis is made of the coupling of junction propagation modes due to the nonlinearity of the Josephson tunneling current which forms vortices. It is shown that a moving vortex array may induce a new type of current steps due to the parametric coupling between electromagnetic waves when the velocity of the moving vortex array coincides with a fraction of the characteristic velocity of the junction propagation modes. It is also shown that the height of the current step which arises when the velocities of moving vortices and electromagnetic waves coincide with each other may be two orders of magnitude smaller than that given by Eck et al. These theoretical results are well demonstrated by the experiment with long Pb–PbOx–Pb Josephson tunnel junctions. © 1979 The Japan Society of Applied Physics.