Coupling of the orthorhombic distortion to the depression of the Tc's due to Zn2+ doping in the ''RE-123'' HTSC's: A (d + s)-wave picture

The depressions of the Tc's of the 123 REBa2Cu3O7 HTSC's due to the substitution of Zn2+ ions into the Cu(2) layer are studied. The orthorhombic distortion which occurs in the 123 ceramics is assumed to induce a modification to the spin-fluctuation (SF) mediated pairing interaction which in turn causes the order parameters of these HTSC's to be of mixed (d + s)-wave symmetry. It is shown that part of the rapid depression of the Tc's caused by Zn2+ substitution into the CuO2 is due to a reduction of the SF-mediated pairing interaction. The differences in the rates of suppression of Tc due to Zn2+ doping in the different RE-123 HTSC's are shown to be due to the changes in the orthorhombicity which depend on the size of the rare earth ions