d-wave peculiarities of YBCO-based Josephson junctions

Abstract

Several configurations of YBa2Cu3Ox (YBCO)-based Josephson junctions have been experimentally investigated. For symmetric 45° grain boundary Josephson junctions was found: (i) The critical current exhibits, as a function of temperature, a local minimum. (ii) The first harmonic of the current phase relationship I(φ) changes sign. For asymmetric 45° grain boundary junctions the current phase relation has been found to be close to sin(2φ). For Nb/Au/(0 0 1)YBCO heterojunctions formed along the c-axis, the finite amplitude of the second harmonic in the current phase relationship was found as well. The results are in good agreement with a microscopic model of Josephson junctions in the frame of the d-wave scenario. © 2002 Elsevier Science B.V. All rights reserved.