Electrodynamics and intrinsic Josephson effects in multi-gap superconductors

Koyama, Tomio*; Ota, Yukihiro; Machida, Masahiko  

We develop a theory for the Josephson effects in 2-gap intrinsic Josephson junctions stacks (IJJs). The coupled dynamical equations for the phase differences are derived from the low-energy effective Lagrangian. The equations describe the longitudinal Josephson plasma and the Josephson-Leggett (JL) mode propagating in the direction perpendicular to the junctions. Numerical results for the - characteristics are presented. The - characteristics shows multiple-branch structures similar to that in Bi-2212 IJJ's. When the Josephson frequency is approached to the JL mode frequency in non-uniform voltage branches, the JL mode is resonantly exited. At the resonant voltage a step-like structure appears in the - curves in low-voltage branches.