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 tunneling in Josephson junctions with GdN ferromagnetic insulator barriers. We prove a clear transition from thermal to quantum regime at a crossover temperature of about 100 mK at zero magnetic field in junctions which demonstrate a clear signature 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.
@article{arxiv.1506.08108,
title = {Macroscopic quantum tunneling in spin filter ferromagnetic Josephson junctions},
author = {D. Massarotti and A. Pal and G. Rotoli and L. Longobardi and M. G. Blamire and F. Tafuri},
journal= {arXiv preprint arXiv:1506.08108},
year = {2015}
}