Abstract
In order to understand the material dependence of within the single-layered cuprates, we study a two-orbital model that considers both and orbitals. We reveal that a hybridization of on the Fermi surface substantially affects in the cuprates, where the energy difference between the and the orbitals is identified to be the key parameter that governs both the hybridization and the shape of the Fermi surface. A smaller tends to suppress through a larger hybridization, whose effect supersedes the effect of diamond-shaped (better-nested) Fermi surface. The mechanism of the suppression of -wave superconductivity due to orbital mixture is clarified from the viewpoint of the ingredients involved in the Eliashberg equation, that is, the Green's functions and the form of the pairing interaction described in the orbital representation. The conclusion remains qualitatively the same if we take a three-orbital model that incorporates the Cu orbital explicitly, where the orbital is shown to have an important effect of making the Fermi surface rounded. We have then identified the origin of the material and lattice-structure dependence of , which is shown to be determined by the energy difference between the two Cu orbitals (primarily governed by the apical oxygen height) and the energy difference between the in-plane and apical oxygens (primarily governed by the interlayer separation ).
6 More- Received 5 December 2011
DOI:https://doi.org/10.1103/PhysRevB.85.064501
©2012 American Physical Society