Comment on a Phys. Rev. Lett. paper: 94 (2005) 146402: Orbital symmetry and Electron Correlation in NaxCoO2

TL;DR

This paper critiques a previous study on NaxCoO2, emphasizing the importance of considering strong electron correlations and spin-orbit coupling for accurate electronic structure modeling.

Contribution

It highlights the necessity of incorporating intra-atomic electron correlations and spin-orbit effects in electronic structure calculations of Co3+ ions.

Findings

Previous model is incorrect without strong correlations.

15 low-lying states within 0.1 eV for Co3+ ions.

Many-electron CEF approach is essential.

Abstract

We argue that the electronic structure considered in a Phys. Rev. Lett. paper 94 (2005) 146402 of the Co3+ ion in the CoO6 octahedron of NaxCoO2 is completely wrong. The presented Fig. 1 is redrawn here as Fig. 1. For physically adequate electronic structure it is necessary to take into account strong intra-atomic electron correlations and spin-orbit coupling. For Co3+ ions there are 15 low lying many-electron states within 0.1 eV as can be obtained in the many-electron CEF approach.