Electron-phonon interaction dressed by electronic correlations near charge ordering as the origin for superconductivity in cobaltates
Abstract
We consider possible routes to superconductivity in hydrated cobaltates Na_xCoO_2.yH_2O on the basis of the t-J-V model plus phonons on the triangular lattice. We studied the stability conditions for the homogeneous Fermi liquid (HFL) phase against different broken symmetry phases. Besides the sqrt(3)xsqrt(3)-CDW phase, triggered by the nearest-neighbour Coulomb interaction V, we have found that the HFL is unstable, at very low doping, against a bond-ordered phase due to J. We also discuss the occurrence of phase separation at low doping and V. The interplay between the electron-phonon interaction and correlations near the sqrt(3)xsqrt(3)-CDW leads to superconductivity in the unconventional next-nearest neighbour f-wave (NNN-f) channel with a dome shape for Tc around x ~ 0.35, and with values of a few Kelvin as seen in experiments. Near the bond-ordered phase at low doping we found tendencies to superconductivity with d-wave symmetry for finite J and x<0.15. Contact with experiments is given along the paper.
Keywords
Cite
@article{arxiv.cond-mat/0608428,
title = {Electron-phonon interaction dressed by electronic correlations near charge ordering as the origin for superconductivity in cobaltates},
author = {A. Foussats and A. Greco and M. Bejas and A. Muramatsu},
journal= {arXiv preprint arXiv:cond-mat/0608428},
year = {2009}
}
Comments
21 pages, 6 figures