Two-orbital view on the origin of the material dependence of Tc in the single-layer cuprates

TL;DR

This paper uses a two-orbital model derived from first-principles calculations to explain how the mixture of dx2-y2 and dz2 orbitals influences the Fermi surface shape and the material dependence of the critical temperature in single-layer cuprates.

Contribution

It introduces a two-orbital model to clarify the relationship between orbital mixing, Fermi surface shape, and Tc in high-temperature cuprates.

Findings

Fermi surface shape varies with orbital mixture.

Material dependence of Tc correlates with Fermi surface curvature.

Square vs. rounded Fermi surfaces explained by tight-binding parameters.

Abstract

Using the dx2-y2+dz2 two orbital model of the high Tc cuprates obtained from the first-principle calculation, we show that the material dependence of the Fermi surface shape can be understood by the degree of the mixture between the dx2-y2$ and the dz2 orbitals. We explain, through investigating the tightbinding hopping integrals, why some cuprates have square shaped Fermi surface, while others have more rounded ones. From this viewpoint, we explain the experimentally observed correlation between the curvature of the Fermi surface and Tc.