Theory of quantum transport in Josephson junctions with a ferromagnetic insulator

We investigate Josephson transport through ferromagnetic insulators (FIs) taking the band structure of the FIs explicitly into account. Using a recursive Green function method, we find that a pi-junction is formed in this type of system. Moreover, an atomic-scale 0-pi oscillation is induced by increasing the thickness of an FI and its oscillation period is universal, exactly equal to a single atomic layer. Based on these results, we show that a stable pi-state can be realized in junctions based on high-T-c superconductors with a La2BaCuO5 barrier. Such FI-based Josephson junctions may become an element in the architecture of future quantum computers. (C) 2010 American Institute of Physics. [doi:10.1063/1.3515524]