We have calculated the optical spectra of NaxCoO2 for x=0.3, 0.5, and 0.7 within the LDA. We compare our results to available experimental data and show that the important features and trends are reproduced well, but there is a nearly uniform shift of peak positions and poor agreement in intensities. We show, through application of a simple model, that these differences can be attributed to overhybridization between Co and O orbitals and spin fluctuations which renormalize the bandwidth. Applying the LDA+U procedure shifts the optical peaks further from their experimental locations, indicating that this method of incorporating correlation effects is ill-suited for the case NaxCoO2.
@article{arxiv.cond-mat/0408696,
title = {Optical Properties and Correlation Effects in NaxCoO2},
author = {M. D. Johannes and I. I. Mazin and D. J. Singh},
journal= {arXiv preprint arXiv:cond-mat/0408696},
year = {2009}
}