Singlet-triplet conversion by tuning Rashba spin-orbit interaction and superconducting phase difference in a Josephson junction

Abstract

We theoretically study a supercurrent in a Josephson junction with a normal metal including Rashba spin-orbit interaction (RM) and ferromagnetic metals by solving Usadel equations. The supercurrent carried by the spin-singlet Cooper pair (SSC) shows a monotonic decrease as a function of the thickness of the RM. On the other hand, it is found that the supercurrent carried by the spin-triplet Cooper pair (STC) exhibits a damped oscillatory behavior as a function of the thickness and the Rashba spin-orbit interaction (RSOI) of RM. These results indicate that the direction of the supercurrent can be controlled by adjusting the thickness and the RSOI. We also reveal that the supercurrent carried by the STC is freely converted to the supercurrent carried by the SSC by tuning the RSOI and the superconducting phase difference. From these results, it is expected that the singlet-triplet conversion can be experimentally achieved, since the superconducting phase difference can be controlled by DC current bias between two superconductors and the RSOI can be adjusted by applying a gate voltage to the RM.