Long-range odd triplet order parameter with equal spin pairing in diffusive Co/In contacts

Abstract

We have measured the conductance of single, double, and multiple junction superconductor (S)/ferromagnet (F) devices made of Co and In. The contacts are created by pinholes in the CoO which prevent the local destruction of superconductivity. The conductance of the single junction has a V-shape cusp at zero bias typical of a nodal order parameter such as $p$ wave. In the double S/F device the nonlocal conductance at low energies is positive and larger in the parallel state than in the antiparallel state by 30%. The same effect was found in multiple S/F junctions in parallel. The results can be explained by an odd triplet order parameter inside S, up to a distance of 150 nm from the S/F interface.