Superconductivity and macroscopic quantum effects in superconducting/ferromagnetic hybrid nanostructures

Abstract

Hybrid nanostructures not only open new routes for studying the coexistence of superconductivity and ferromagnetism, but they also provide new insights into the fundamentals of quantum electronics. We have investigated, by a series of experiments, the change in the superconducting wavefunction resulting from the interaction between the spins of a Cooper pair and the exchange field. Tunneling spectroscopy reveals an inhomogeneous Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) superconducting state induced in a ferromagnetic thin film by the proximity effect. As a consequence, critical current and macroscopic quantum interference (SQUID) experiments show π-coupling between two superconductors coupled through a ferromagnetic thin film. π-coupling originates a spontaneous half quantum flux in a superconducting ring. This phase transition has been observed by Josephson and Hall magnetometry. To cite this article: M. Aprili et al., C. R. Physique 7 (2006).