Comment on "Quantum Monte Carlo Evidence for Superconductivity in the Three-Band Hubbard Model in Two Dimensions"

TL;DR

This comment critiques a recent QMC study on the three-band Hubbard model, arguing that the parameter choices are inappropriate and that the observed pairing correlations do not conclusively demonstrate superconductivity.

Contribution

It clarifies the limitations of previous QMC results by highlighting parameter issues and the interpretation of pairing correlations in the three-band Hubbard model.

Findings

Parameter set used is not suitable for high-T_c materials.

Observed pairing correlations are not definitive evidence of superconductivity.

The increase in correlations is due to non-vertex contributions.

Abstract

In a recent Letter, Kuroki and Aoki [Phys. Rev. Lett. 76, 440 (1996)] presented quantum Monte-Carlo (QMC) results for pairing correlations in the three-band Hubbard model, which describes the Cu-d_{x^2-y^2} and O-p_{x,y} orbitals present in the CuO_2 planes of high-T_c materials. In this comment we argue that (i) the used parameter set is not appropriate for the description of high-T_c materials since it does not satisfy the minimal requirement of a charge-transfer gap at half-filling, and (ii) the observed increase in the d_{x^2-y^2} channel is dominantly produced by the pair-field correlations without the vertex part. Hence, the claim of evidence of ODLRO is not justified.