The superconducting properties of the highly anisotropic cuprate-supercon-ductors Tl_2Ba_2Ca_2Cu_3O_(10+δ) (TBCCO) and Bi_2Sr_2CaCu_2O_(8+δ) (BSCCO) are well described by a stack of Josephson junctions coupling the superconducting CuO_2 layers in c-direction. In particular the multiple branch structure observed in the current-voltage characteristics by several groups can be explained by this model. Due to the low value of the critical current in c-direction the system has a small Josephson plasma frequency ω_p and a large value of the McCumber parameter ω_c. Therefore the current-voltage characteristics are highly hysteretic. The low value of the Josephson plasma frequency manifests itself in the transparency of the stack with respect to THz radiation polarized in c-direction. The longitudinal and transversal plasma oscillations have also been observed directly.
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