Electron Correlation and Fermi Surface Topology ofNaxCoO2

Abstract

The electronic structure of NaxCoO2 revealed by recent photoemission experiments shows important deviations from band theory predictions. The six small Fermi surface pockets predicted by local-density approximation calculations have not been observed as the associated e'(g) band fails to cross the Fermi level for a wide range of sodium doping concentration x. In addition, significant bandwidth renormalizations of the t(2g) complex have been observed. We show that these discrepancies are due to strong electronic correlations by studying the multiorbital Hubbard model in the Hartree-Fock and strong-coupling Gutzwiller approximation. The quasiparticle dispersion and the Fermi surface topology obtained in the presence of strong local Coulomb repulsion are in good agreement with experiments.

Magnetic phase transition at88KinNa0.5CoO2Pedrini1, Gavilano2, Felder3 et al. 2005Phys. Rev. B131140View full textAdd to dashboardCite

“…The calculations predict both the Fermi surface pocket cancellation and a band narrowing [21], again in good agreement with the results of ARPES measurements [22] at x = 0.5. With a similar approach, the authors of Ref.…”

“…At this point, we note that the substantial enhancement of the effective electron mass for Na 0.5 CoO 2 , evaluated from the high-temperature saturation value of χ and cited above in Eq. (15), is an order of magnitude larger with respect to the result of an LSDA+U calculation [21].…”

Self-energy corrections to anisotropic Fermi surfaces

“…9 However, the interpretation of the data obtained by different experimental techniques in anisotropic strongly correlated systems remains a complex task. 10 The Fermi surface depends on the self-energy corrections to the quasiparticle energies, which, in turn, depend on the shape of the Fermi surface. Hence, there is an interplay between the self-energy corrections and the Fermi surface topology.…”

Spin fluctuations, magnetic long-range order, and Fermi surface gapping inNaxCoO2

“…A second explanation would involve the e ′ g character hole pockets that were intensely sought for in numerous ARPES studies. In a rigid band picture these should rather disappear with increasing Fermi level which has also been predicted by numerous theoretical studies 14,37 and recently been claimed to be observed experimentally 38 . Even if the hole pockets were stabilized also for higher x as predicted by some models 13,39 , the DOS behaviour observed here could hardly be explained.…”