Direct coupling between magnetism and superconducting current in Josephson φ0 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 non-sinusoidal current-phase relation. The ground state of this junction is caracterized by the finite phase difference φ 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 φ 0 junction formation gives a direct coupling between the superconducting current and the magnetic moment in the weak link. Therefore the φ 0 junctions open interesting perspectives for the superconducting spintronics. Usually the current-phase relations in Josephson junctions near the critical temperature are sinusoidal j(φ) = jc sin(φ) but with lowering temperature the contribution of the higher harmonic terms ∼ jn sin(nφ) can be observed. However if the time reversal symmetry is preserved the current-phase relation is always antisymmetric j(−φ) = −j(φ) [1]. Without this restriction a more general j(φ) = j0 sin(φ + φ0) dependence is also possible and the generic expression for the current in the pioneering work of Josephson [2] incorporates this possibility. In fact such current-phase relations have been predicted for Josephson coupling involving the unconventional superconductors [3],[4],[5],[6]. The experimental verification of these predictions are still lacking. In the present work we demonstrate that the Josephson superconductor/normal metal/superconductor junctions (S/N/S) provides the realization of such unusual current-phase relations j(φ) = j0 sin(φ+ φ0) for the case of conventional superconductors when the normal layer is a non-centrosymmetric, i. e. with broken inversion symmetry (BIS) magnetic metal. Further on we will call this