A 59Co NMR study of CoO2, the x=0 end member of AxCoO2 (A = Na, Li...) cobaltates, reveals a metallic ground state, though with clear signs of strong electron correlations: low-energy spin fluctuations develop at wave vectors q different from 0 and a crossover to a Fermi-liquid regime occurs below a characteristic temperature T*~7 K. Despite some uncertainty over the exact cobalt oxidation state n this material, the results show that electronic correlations are revealed as x is reduced below 0.3. The data are consistent with NaxCoO2 being close to the Mott transition in the x -> 0 limit.
Cite
@article{arxiv.cond-mat/0701595,
title = {Electronic Correlations in CoO2, the Parent Compound of Triangular Cobaltates},
author = {C. de Vaulx and M. -H. Julien and C. Berthier and S. Hebert and V. Pralong and A. Maignan},
journal= {arXiv preprint arXiv:cond-mat/0701595},
year = {2009}
}