title: Macroscopic quantum tunnelling in spin filter ferromagnetic Josephson junctions.
abstract: The interfacial coupling of two materials with different ordered phases, such as a superconductor (S) and a ferromagnet (F), is driving new fundamental physics and innovative applications. For example, the creation of spin-filter Josephson junctions and the demonstration of triplet supercurrents have suggested the potential of a dissipationless version of spintronics based on unconventional superconductivity. Here we demonstrate evidence for active quantum applications of S-F-S junctions, through the observation of macroscopic quantum tunnelling in Josephson junctions with GdN ferromagnetic insulator barriers. We show a clear transition from thermal to quantum regime at a crossover temperature of about 100 mK at zero magnetic field in junctions, which present clear signatures of unconventional superconductivity. Following previous demonstration of passive S-F-S phase shifters in a phase qubit, our result paves the way to the active use of spin filter Josephson systems in quantum hybrid circuits.
authors.affiliation: 1] Dipartimento di Fisica, Università degli Studi di Napoli 'Federico II', Monte S.Angelo, I-80126 Napoli, Italy [2] CNR-SPIN UOS Napoli, Monte S.Angelo-via Cinthia, I-80126 Napoli, Italy.
authors.forename: D
authors.identifier: 0000000157400054
authors.initials: D
authors.lastname: Massarotti
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: A
authors.initials: A
authors.lastname: Pal
authors.affiliation: Dipartimento di Ingegneria Industriale e dell'Informazione, Seconda Università degli Studi di Napoli, I-81031 Aversa (Ce), Italy.
authors.forename: G
authors.initials: G
authors.lastname: Rotoli
authors.affiliation: 1] Dipartimento di Ingegneria Industriale e dell'Informazione, Seconda Università degli Studi di Napoli, I-81031 Aversa (Ce), Italy [2] American Physical Society, 1 Research Road, Ridge, New York 11961, USA.
authors.forename: L
authors.identifier: 0000000279666926
authors.initials: L
authors.lastname: Longobardi
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: M G
authors.initials: MG
authors.lastname: Blamire
authors.affiliation: 1] CNR-SPIN UOS Napoli, Monte S.Angelo-via Cinthia, I-80126 Napoli, Italy [2] Dipartimento di Ingegneria Industriale e dell'Informazione, Seconda Università degli Studi di Napoli, I-81031 Aversa (Ce), Italy.
authors.forename: F
authors.initials: F
authors.lastname: Tafuri