Band structure renormalization and weak pseudogap behavior in Na0.33CoO2:: Fluctuation exchange study based on a single-band model

Based on a single-band Hubbard model and the fluctuation exchange approximation, the effective mass and the energy band renormalization in Na0.33CoO2 is elaborated. The renormalization is observed to exhibit certain kind of anisotropy, which agrees qualitatively with the angle-resolved photoemission spectroscopy measurements. Moreover, the spectral function and density of states in the normal state are calculated, with a weak pseudogap behavior being seen, which is explained as a result of the strong Coulomb correlations. Our results suggest that the large Fermi surface associated with the a(1g) band plays likely a central role in the charge dynamics.