Electronic mechanism of critical temperature variation in RBa2Cu3O7−δ

We have performed systematic studies of the trend of the critical temperature Tc due to both Madelung site potential difference between in-plane oxygen and copper sites ΔVM and interlayer effect in the optimally doped 123 superconductors RBa2Cu3O7−δ. ΔVM is found to decrease with the increase of the trivalent rare-earth ionic radius rR3+. This change enhances the next-nearest-neighbor hopping integral t', which results in the experimentally observed increase of Tc with rR3+. The coherent interlayer single-particle hopping t⊥ has a more profound effect than t' on the nearly linear trend of Tc as a function of rR3+. These results reveal the importance of the electronic origin of the rare-earth ionic size effect on Tc in this family.Published versio