Reentrance of Macroscopic Quantum Tunneling in Cuprate Superconductors
We present a theoretical analysis of the transition from thermal activation (TA) regime to the macroscopic quantum tunneling (MQT) regime of the decay from a metastable persistent current state in grain boundary junctions of cuprate superconductors. This transition is conventionally characterized by a single crossover temperature determined by the potential profile and dissipative mechanisms. It is shown that due to the existence of low energy bound states (mid-gap states) for various relative orientations of the crystal axes, there exists a window of parameters where one finds, with lowering temperature, an inverse crossover from MQT to TA, followed by a subsequent reentrance of MQT. It is shown that these predictions are in reasonable agreement with recent experiments.
Pietro VINCENZINI, David S. GINLEY, Giovanni BRUNO, Attilio RIGAMONTI and Nikolay ZHELUDEV
J. Michelsen and V. S. Shumeiko, "Reentrance of Macroscopic Quantum Tunneling in Cuprate Superconductors", Advances in Science and Technology, Vol. 75, pp. 155-160, 2010