Intrinsic Josephson pi-junctions for novel devices

Abstract

The properties of YBCO grain boundary Josephson junctions have been studied experimentally. Due to the d-wave symmetry of the order parameter of YBCO it is possible to have junctions with a 0-π phase discontinuity along the barrier profile. Such 0-π-junctions can have a ground state where spontaneous flux is generated at the discontinuity point. This work has been focused on understanding if it is possible to fabricate biepitaxial grain boundary 0-π-junctions that, despite the unavoidable faceting along the grain boundary line, can have a ground state with spontaneously generated flux. The interest in the biepitaxial technique lies in its flexibility for circuit design. The microstructure and transport properties of the grain boundary junctions have been studied in details. Scanning SQUID Microscope imaging has revealed the presence of spontaneous flux in our junctions. Finally the dynamics of 0-π-junctions compared to conventional 0-junctions have been studied and compared to simulation.