Josephson plasma oscillation in high-Tc superconductors

Strongly anisotropic high-Tc superconductors (HTSC) behaves as stacks of superconductor-insulator-superconductor (SIS) tunnel junctions. This peculiar electronic structure is responsible for the unusual electrodynamic and magnetic properties in the superconducting state. To study the electromagnetic response in the c-axis of HTSC, the microwave response was measured in the frequency range from 30 GHz to 150 GHz. A sharp magnetoabsorption, which can be attributed to the collective longitudinal Josephson plasma resonance, is observed in the superconducting state of extremely anisotropic Bi2Sr2CaCu2O8+δ. We show that this resonance is a powerful means to prove the nature of the Josephson coupling and the nature of the vortex state. (author)