Band structure renormalization and weak pseudogap behavior in Na_{0.33}CoO_2: Fluctuation exchange study based on a single band model

TL;DR

This study uses a single band Hubbard model and fluctuation exchange approximation to analyze band structure renormalization and weak pseudogap behavior in Na_{0.33}CoO_2, aligning with experimental ARPES data.

Contribution

It provides a theoretical analysis of anisotropic band renormalization and pseudogap phenomena in Na_{0.33}CoO_2 using a single band model and fluctuation exchange approximation.

Findings

Anisotropic band renormalization consistent with ARPES measurements

Observation of weak pseudogap behavior due to strong Coulomb correlations

Large Fermi surface associated with the a_{1g} band influences charge dynamics

Abstract

Based on a single band Hubbard model and the fluctuation exchange approximation, the effective mass and the energy band renormalization in Na$_{0.33}$CoO$_2$ is elaborated. The renormalization is observed to exhibit certain kind of anisotropy, which agrees qualitatively with the angle-resolved photoemission spectroscopy (ARPES) measurements. Moreover, the spectral function and density of states (DOS) 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 (FS) associated with the $a_{1g}$ band plays likely a central role in the charge dynamics.