JOSEPHSON PLASMA IN CUPRATE HIGH T-C SUPERCONDUCTORS

The nature of the I-V characteristics along the c axis of Bi2Sr2CaCu2O 8+delta is explained on a model in which the superconducting CuO2 laye rs are coupled by the Josephson effect through the block layers. In th is model the Josephson plasma is generated by the coupling between the Josephson current flowing along the c axis and the electromagnetic fi eld. The longitudinal and transverse plasma waves propagating along th e c axis and in the ab-plane respectively have quite different nature. The Josephson plasma waves in high T-c superconductors have been obse rved by reflectivity measurements of far infrared light and experiment s of microwave absorption. The Josephson plasma strongly interacts wit h the vortices introducted by an external magnetic field Therefore, th e plasma frequency strongly depends on the vortex states such as the v ortex liquid and solid states and on the vortex species like pancake a nd Josephson vortices.