Quantum crossover in moderately damped epitaxial NbN/MgO/NbN junctions   with low critical current density
  High quality epitaxial NbN/MgO/NbN Josephson junctions have been realized with MgO barriers up to a thickness of d=1 nm. The junction properties coherently scale with the size of barrier, and low critical current densities down to 3 A/cm$^2$ have been achieved for larger barriers. In this limit, junctions exhibit macroscopic quantum phenomena for temperatures lower than 90 mK. Measurements and junction parameters support the notion of a possible use of these devices for multiphoton quantum experiments, taking advantage of the fast non equilibrium electron-phonon relaxation times of NbN. 
Luigi Longobardi, Davide Massarotti, Giacomo Rotoli, Daniela   Stornaiuolo, Gianpaolo Papari, Akira Kawakami, Giovanni Piero...
cond-mat.supr-con