CRITICAL CURRENT OF JOSEPHSON-COUPLED SYSTEMS IN PERPENDICULAR FIELDS

We calculate the magnetic field and temperature dependence of the critical current density j(c) along the c axis in Josephson-coupled layered systems when the applied magnetic field is parallel to the c axis. j(c) decreases with field and temperature because of the thermal fluctuations of the vortices which induce a phase difference across the junctions. The anisotropy ratio gamma is-proportional-to 1/square-root j(c) acquires a field and temperature dependence. The decoupling phase transition line above which the superconducting current along the c axis vanishes is determined.