Comment on "Relevance of Cu-3d multiplet structure in models of high Tc cuprates''

TL;DR

This paper critiques a recent model of cuprates, clarifying that the ground-state overlap with Zhang-Rice singlets is approximately 94%, challenging previous claims of only 50% overlap based on a different representation.

Contribution

It clarifies the correct interpretation of the ground-state overlap in cuprate models, emphasizing the importance of proper low-energy reduction procedures.

Findings

Ground-state overlap with ZRS is near 94%

Previous 50% estimate was based on a different representation

Correct interpretation aligns with known reduction procedures

Abstract

In a recent work [M. Jiang, M. Moeller, M. Berciu, and G. A. Sawatzky, Phys. Rev. B \textbf{101}, 035151 (2020)], the authors solved a model with a Cu impurity in an O-2p band as an approximation to the local electronic structure of a hole doped cuprate. One of their conclusions is that the ground-state has only $\sim 50$ \% overlap with a Zhang-Rice singlet (ZRS). This claim is based on the definition of the ZRS in a different representation, in which the charge fluctuations at the Cu site have been eliminated by a canonical transformation. The correct interpretation of the results, based on known low-energy reduction procedures for a multiband model including 3d$^8$ and 3d$^{10}$ configurations of Cu, indicates that this overlap is near 94 \%.