We derive an effective Hamiltonian for highly correlated t2g states centered at the Co sites of NaxCoO2. The essential ingredients of the model are an O mediated hopping, a trigonal crystal-field splitting, and on-site effective interactions derived from the exact solution of a multi-orbital model in a CoO6 cluster, with parameters determined previously. The effective model is solved by dynamical mean-field theory (DMFT). We obtain a Fermi surface (FS) and electronic dispersion that agrees well with angle-resolved photoemission spectra (ARPES). Our results also elucidate the origin of the "sinking-pockets" in different doping regimes.
@article{arxiv.0901.1834,
title = {Dynamical mean field theory of an effective three-band model for Na$_x$CoO$_2$},
author = {A. Bourgeois and A. A. Aligia and M. J Rozenberg},
journal= {arXiv preprint arXiv:0901.1834},
year = {2009}
}