Pair symmetry and degree of gap depression at S-I interfaces in HTS Josephson junctions

A new possible indirect way of testing pair symmetry in high-Tc superconduc tors has been set up. The degree of intrinsic gap depression at Superconduc tor-Insulator [S-I] interfaces required to match I-c(T)R-n(T) data in I-ITS Josephson junctions depends on the pair symmetry of the material itself, s o that an higher fraction of d-wave symmetry for the order parameter requir es less gap depression, while an higher fraction of s-wave corresponds to a larger degree of gap depression. In order to obtain a general reference va lue for the intrinsic amount of gap depression at S-I interfaces the de Gen nes condition has been used, and resulting reduced Ic(T)Rn(T) data have bee n calculated in the framework of a mixed (s+id)-wave pair symmetry for the depressed order parameter ranging from pure s to pure d-wave. This model ha s been tentatively applied to two junctions' made of very different HTSs: Y BCO and BKBO, yielding a result of almost pure d-wave for YBCO and of pure s-wave for BKBO.