The c-axis coherent response of Bi-2212 Josephson flux-flow junction to mm-wave radiation

Authors found a coherent response of Josephson flux-flow in a long Bi-2212 stacked junction to an external microwave field with E-component oriented parallel to the c-axis. The response appears as Shapiro steps on the flux-flow branch of the I-V characteristic. The steps appear only at high enough fields corresponding to the formation of a dense Josephson vortex lattice. The result implies coherency of the Josephson flux-flow in both directions, along the a- and the c-axis over the total thickness of the stack. 20 refs.