Coulomb correlations do not fill the e<Superscript>′</Superscript> <Subscript>g</Subscript> hole pockets in Na<Subscript>0.3</Subscript>CoO<Subscript>2</Subscript>

There exists presently considerable debate over the question whether local Coulomb interactions can explain the absence of the small e<Superscript>′</Superscript> <Subscript>g</Subscript> Fermi surface hole pockets in photoemission studies of Na<Subscript>0.3</Subscript>CoO<Subscript>2</Subscript>. By comparing dynamical mean field results for different single particle Hamiltonians and exact diagonalization as well as quantum Monte Carlo treatments, we show that, for realistic values of the Coulomb energy U and Hund exchange J, the e<Superscript>′</Superscript> <Subscript>g</Subscript> pockets can be slightly enhanced or reduced compared to band structure predictions, but they do not disappear. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2008