Physikalisches Kolloquium "Singlet-Triplet Mixing in Josephson Junctions with Rotating Magnetization"

Superconductivity and magnetism may coexist and intertwine in some systems. Known for a long time is the case of antiferromagnetic superconductors. There are other, less obvious situations where the superconducting state accommodates itself with the presence of magnetism. We discuss how the singlet-triplet mixing of the order parameter allows nanoscale magnetic junctions to carry a Josephson current through very wide ferromagnets with rotating magnetization.The effect is described in terms of a cascading of singlet and triplet components and illustrated with a magnetic multilayer. We show how the current can be tuned with the twisting of the magnetization. Finally, we also introduce a new kind of Josephson current reversal, the triplet 0 − π transition, that can be observed in one and the same system either by twisting the domain wall or by varying temperature.