INTRINSIC SURFACE DEPRESSION OF THE ORDER-PARAMETER UNDER MIXED (S-WAVE PAIR SYMMETRY AND ITS EFFECT ON THE CRITICAL-CURRENT OF HIGH-T-C SIS JOSEPHSON-JUNCTIONS(ID))

An intrinsic gap depression at the superconductor-insulator interface due to the very short value of the coherence length in high-T-c superc onductors [HTS] is considered in the framework of a mixed (s + id)-wav e pair symmetry for the order parameter ranging from pure s to pure d- wave. This gap depression acts as the main physical agent causing the relevant reduction of I-c(T)R-n(T) values with respect to BCS expectat ions in HTS SIS Josephson junctions. Good agreement with various exper imental data is obtained with both pure s-wave and pure d-wave symmetr ies of the order parameter, but with amounts of gap depression dependi ng on the pair symmetry adopted. Regardless of the pair symmetry consi dered, these results prove the importance of the surface order-paramet er depression in the correct interpretation of the I-c(T)R-n(T) data i n HTS SIS junctions. In the case of a planar YBCO-based junction the u se of the de Gennes condition allowed us to tentatively obtain an uppe r limit for the amount of d-wave present in the gap of YBCO.