Electronic mechanism of critical temperature variation in RBa2Cu3O7-δ -: art. no. 094512

We have performed systematic studies of the trend of the critical temperature T-c due to both Madelung site potential difference between in-plane oxygen and copper sites Delta V-M and interlayer effect in the optimally doped 123 superconductors RBa2Cu3O7-delta Delta V-M is found to decrease with the increase of the trivalent rare-earth ionic radius r(R3+). This change enhances the next-nearest-neighbor hopping integral t', which results in the experimentally observed increase of T-c with r(R3+). The coherent interlayer single-particle hopping t(perpendicular to) has a more profound effect than t' on the nearly linear trend of T-c as a function of r(R3+). These results reveal the importance of the electronic origin of the rare-earth ionic size effect on T-c in this family.