A diagrammatic approach for a clean double-barrier ferromagnetic Josephson junction

Abstract

We consider a double-barrier superconductor/ferromagnet/superconductor (S/I/F/I/S) ballistic junction with thin insulating layers at the interfaces. Using a diagrammatic approach we obtain the Andreev spectrum and the supercurrent in terms of the S/F interface scattering amplitudes. We use the rules devised for the summation of the multiple scattering diagrams. We especially concentrate on the strong interface scattering and consider the evolution of the supercurrent. We observe that in this case the normal spin-up and spin-down electron (hole) resonances determine well the supercurrent, except near the strong peaks, where the Andreev diagrams are also important. At lower Z ≈ 2 values we also need to keep other closed loops. We consider both the one- and three-dimensional cases. We also consider the case of strong band misfit. The current–phase relation shows a broad range of behavior with 0–π regions and transitions where higher harmonics in the phase contribute dominantly.