Ultrafast Photoresponse of Superconductor/Ferromagnet Nano-Layered Hybrids

Interactions of superconducting nanostructures with external optical radiation represent a very interesting topic in both the framework of nonequilibrium physics and photodetector applications. Heterogeneous nano-layers, such as proximized superconductor/normal metal and superconductor/ferromagnet (S/F) bilayers, are very promising since they exhibit the ultrafast Cooper-pair and quasiparticle dynamics. We have characterized Nb/NiCu, NbN/NiCu, YBaCuO/Au/NiCu, and YBaCuO/LaSrMnO proximized S/F nano-bilayers, using time-resolved, all-optical, femtosecond pump-probe spectroscopy measurements down to 4 K. Our experiments demonstrate that these bilayers are very promising for novel, ultrafast photodetection and spintronics device applications. Moreover, our time-resolved studies of the carrier dynamics in oxide-based S/F structures open the way to novel basic-physics investigations of nonequilibrium effects in correlated systems.