Direct Coupling Between Magnetism and Superconducting Current in the Josephson ${\phi }_0$ Junction

We study the proximity effect between conventional superconductor and magnetic normal metal with a spin-orbit interaction of the Rashba type. Using the phenomenological Ginzburg-Landau theory and the quasiclassical Eilenberger approach it is demonstrated that the Josephson junction with such a metal as a weak link has a special nonsinusoidal current-phase relation. The ground state of this junction is characterized by the finite phase difference ${\phi }_0$, which is proportional to the strength of the spin-orbit interaction and the exchange field in the normal metal. The proposed mechanism of the ${\phi }_0$ junction formation gives a direct coupling between the superconducting current and the magnetic moment in the weak link. Therefore the ${\phi }_0$ junctions open interesting perspectives for the superconducting spintronics.

Figure 1

Geometry of Josephson junction with BIS metal as a weak link. The exchange field is directed along the $z$ axis and the $\mathbf{n}$ vector is along the $y$ axis. The total length of the weak link is $2L$.