Oxygen hole content, charge-transfer gap, covalency, and cuprate superconductivity

TL;DR

This paper demonstrates through modeling that high oxygen hole content and low charge-transfer gap are crucial for optimal superconductivity in cuprates, highlighting copper's unique covalency role.

Contribution

It provides a theoretical explanation linking experimental observations to the three-band Hubbard model, emphasizing copper's covalency in cuprate superconductivity.

Findings

Large oxygen hole content correlates with higher T_c.

Large charge-transfer gap suppresses superconductivity.

Cuprates' unique covalency is key to their superconducting properties.

Abstract

Experiments have shown that the families of cuprate superconductors that have the largest transition temperature at optimal doping also have the largest oxygen hole content at that doping. They have also shown that a large charge-transfer gap, a quantity accessible in the normal state, is detrimental to superconductivity. We solve the three-band Hubbard model with cellular dynamical mean-field theory and show that both of these observations follow from the model. Cuprates play a special role amongst doped charge-transfer insulators of transition metal oxides because copper has the largest covalent bonding with oxygen.