dc Josephson effect in a junction between two ferromagnetic superconductors

By using the Furusaki–Tsukada formula, we calculate Josephson current in a junction between two ferromagnetic superconductors (FSs) as a function of temperature, exchange field and insulator barrier strength of interface between FSs. We consider FSs in three different Cooper pairing states: spin singlet s-wave pairing (SWP) state, spin triplet opposite spin pairing (OSP) state and spin triplet equal spin pairing (ESP) state. It is found that the FS exchange field suppresses dc Josephson current for SWP and OSP states while it does not show any sensitivity to exchange field in the case of ESP state. Also, at low temperature and high barrier strength, dc Josephson current shows clearly different curves for SWP, OSP and ESP states. Therefore, our results can help to discriminate the kind of Cooper pair symmetry in ferromagnetic superconductors.