The ground states of NaxCoO2 (0.0<x<1.0) is studied by the LDA+Gutzwiller approach, where charge transfer and orbital fluctuations are all self-consistently treated {\it ab-initio}. In contrast to previous studies, which are parameter-dependent, we characterized the phase diagram as: (1) Stoner magnetic metal for x>0.6 due to a1g van-Hove singularity near band top; (2) correlated non-magnetic metal without eg′ pockets for 0.3<x<0.6; (3) eg′ pockets appear for x<0.3, and additional magnetic instability involves. Experimental quasi-particle properties is well explained, and the a1g-eg′ anti-crossing is attributed to spin-orbital coupling.
@article{arxiv.0801.4184,
title = {Phase Diagram of Na$_x$CoO$_2$ Studied by Gutzwiller Density Functional Theory},
author = {Guangtao Wang and Xi Dai and Zhong Fang},
journal= {arXiv preprint arXiv:0801.4184},
year = {2009}
}