Coherent current states in a two-band superconductor

Homogeneous current states in thin films and Josephson current in superconducting microbridges are studied within the framework of a two-band Ginzburg-Landau theory. By solving the coupled system of equations for two order parameters the depairing current curves and Josephson current-phase relation are calculated for different values of phenomenological parameters gamma and eta. Coefficients gamma and eta describe the coupling of order parameters (proximity effect) and their gradients (drag effect), respectively. For definite parameter values the dependence of the current j on the superfluid momentum q contains local minima and corresponding bistable states. It is shown that a Josephson microbridge made from two-band superconductors can demonstrate pi-junction behavior. (c) 2007 American Institute of Physics.