Coherent current states in a two-band superconductor

TL;DR

This paper investigates homogeneous current states and Josephson effects in two-band superconductors using Ginzburg-Landau theory, revealing bi-stability and pi-junction behavior depending on coupling parameters.

Contribution

It introduces a detailed analysis of current-phase relations and depairing currents in two-band superconductors, highlighting the effects of coupling parameters on stability and junction behavior.

Findings

Current dependence on superfluid momentum shows local minima and bi-stability.

Josephson microbridge can exhibit pi-junction behavior.

Coupling parameters influence the current and stability of states.

Abstract

Homogeneous current states in thin films and Josephson current in superconducting microbridges are studied within the frame 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 values of parameters the dependence of current j on superfluid momentum contains local minimum and corresponding bi-stable states. It is shown that the Josephson microbridge from two-band superconductor can demonstrate pi-junction behaviour.