Fluctuation Exchange Analysis of Superconductivity in the Standard Three-Band CuO2 Model

TL;DR

This paper uses the FLEX approximation to analyze superconductivity in a three-band CuO2 model, revealing good agreement with experiments and emphasizing the role of orbital antiferromagnetic order in underdoped regimes.

Contribution

It applies the FLEX method to a realistic three-band model, incorporating Coulomb interactions, and provides detailed doping-dependent insights into superconductivity and competing orders.

Findings

Transition temperatures match experimental values in overdoped regime.

Orbital antiferromagnetic order is significant in underdoped regime.

Doping dependence of superconductivity is characterized with no free parameters.

Abstract

The fluctuation exchange, or FLEX, approximation for interacting electrons is applied to study instabilities in the standard three-band model for CuO2 layers in the high-temperature superconductors. Both intra-orbital and near-neigbor Coulomb interactions are retained. The filling dependence of the d(x2-y2) transition temperature is studied in both the "hole-doped" and "electron-doped" regimes using parameters derived from constrained-occupancy density-functional theory for La2CuO4. The agreement with experiment on the overdoped hole side of the phase diagram is remarkably good, i.e., transitions emerge in the 40 K range with no free parameters. In addition the importance of the "orbital antiferromagnetic," or flux phase, charge density channel is emphasized for an understanding of the underdoped regime.