SIMPLE-MODEL FOR THE DC FLUX TRANSFORMER IN LAYERED SUPERCONDUCTORS WITH JOSEPHSON COUPLING

We present a model for the dc flux transformer configuration in layered superconductors with Josephson coupling. It consists of a simple extension of a model introduced by Clem for the traditional dc flux transformer, but including Josephson coupling and dissipation between planes. We calculate the nonlinear current-voltage characteristics for different cases. We find two kinds of behavior. For weak pinning or strong interplane coupling (both due to magnetic forces and Josephson effect) there is an onset of dissipation with the same voltages in both the top and the bottom faces of the sample, at a given critical current. At a higher current there is a decoupling of the two faces where they have different voltages. This corresponds to a cutting of the vortices that occurs between the first (top) and the second planes. The decoupling current is independent of pinning and vanishes linearly with temperature close to Tc. For strong pinning or weak interplane coupling, each face behaves independently with corresponding different critical currents for the onset of dissipation and different voltages. © 1995 The American Physical Society.