Electronic structure and Fermi-surface topology of NaxCoO2

A. BOURGEOIS, A A ALIGIA, T. KROLL AND M. D. NÚÑEZ REGUEIRO

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

APS

Año: 2007 vol. 75 p. 17 - 4518

0163-1829

   We construct an effective Hamiltonian for the motion of T2g highly correlated states in NaxCoO2. We solve exactly a multiband model in a CoO6 cluster with electronic occupation corresponding to a nominal Co valence of either +3 or +4. Using the ensuing ground states, we calculate the effective O mediated hopping t = 0.10 eV between many-body T2g states and estimate the direct hopping t´= 0.05 eV. The trigonal splitting 3D = 0.315 eV is taken from recent quantum chemistry calculations. The resulting effective Hamiltonian is solved using a generalized slave-boson mean-field approximation. The results show a significant band renormalization and a Fermi-surface topology that agrees with experiment, in contrast to predictions using the local-density approximation.