Quasiparticle dispersion near the Fermi surface in Na$_x$CoO$_2$

TL;DR

This paper develops an effective three-band Hamiltonian for Na_xCoO_2 to accurately describe quasiparticle dispersion near the Fermi surface, aligning well with experimental ARPES data.

Contribution

It introduces a novel three-band model with parameters derived from cluster calculations, improving the understanding of correlated electron behavior in Na_xCoO_2.

Findings

Band renormalization is significant

Dispersion near the Fermi surface matches ARPES data

Contrasts with local-density approximation predictions

Abstract

We construct an effective Hamiltonian for the motion of t2g highly correlated states in NaxCoO2. This three-band model includes the indirect Co-O-Co hopping t and the crystal-field splitting 3D. Calculations in a CoO6 cluster give the effective parameters t=100 meV and 3D=315 meV. The Hamiltonian is solved using a generalized slave-boson mean-field approximation. The results show a significant band renormalization. Without any additional hypothesis, the dispersion of the bands near the Fermi energy and Fermi surface topology agrees with angle-resolved photoemission experiments, in contrast to predictions using the local-density approximation.