QUANTITATIVE MODEL FOR THE SUPERCONDUCTIVITY SUPPRESSION IN R(1-X)PR(X)BA(2)CU(3)O(7) WITH DIFFERENT RARE

We report local density approximation plus Hubbard parameter U calculations of the electronic structure of ABa2Cu3O7 (A=Y,Pr,Nd) including Coulomb correlations in the f shell. For A=Pr (but not for A=Nd) an additional band crosses the Fermi level, grabbing holes from the (super)conducting pdσ band. On doping Y or Nd with Pr the position of the hole-depleting band depends on the atomic number of the host rare earth, through the position of its f level. This makes Tc suppression in doped compounds different for different hosts the stronger the smaller the atomic number of the host is, and also explains why an external pressure reduces Tc in doped compounds, opposite to the effect of the "chemical pressure" (substituting one rare earth by another with a smaller size). © 1995 The American Physical Society.