Anomalous quasiparticle renormalization in Na0.73CoO2: role of interorbital interactions and magnetic correlations

Phys Rev Lett. 2007 Jul 27;99(4):046403. doi: 10.1103/PhysRevLett.99.046403. Epub 2007 Jul 25.

Abstract

We report an angular resolved photoemission study of NaxCoO2 with x approximately 0.73 where it is found that the renormalization of the quasiparticle (QP) dispersion changes dramatically upon a rotation from GammaM to GammaK. The comparison of the experimental data to the calculated band structure reveals that the quasiparticle renormalization is most pronounced along the GammaK direction, while it is significantly weaker along the GammaM direction. We discuss the observed anisotropy in terms of multiorbital effects and point out the relevance of magnetic correlations for the band structure of NaxCoO2 with x approximately 0.75.