Cooperative effect of phonons and electronic correlations for superconductivity in cobaltates

TL;DR

This paper suggests that the superconductivity in hydrated sodium cobaltate arises from a cooperative effect between electronic correlations and electron-phonon interactions, explaining the observed dome-shaped phase diagram near a specific doping level.

Contribution

It introduces a model combining electronic correlations and phonons to explain unconventional superconductivity in cobaltates, highlighting the role of Coulomb interactions and charge density wave proximity.

Findings

Evidence for unconventional superconductivity in the model

Realistic critical temperature ($T_c$) values obtained

Dome-shaped phase diagram near doping level x ~ 0.35

Abstract

We propose that unconventional superconductivity in hydrated sodium cobaltate $Na_xCoO_2$ results from an interplay of electronic correlations and electron-phonon interactions. On the basis of the $t-V$ model plus phonons we found evidences for a) unconventional superconductivity, b) realistic values of $T_c$ and c) the dome shape existing near $x \sim 0.35$. This picture is obtained for $V$ close to the critical Coulomb repulsion $V_c$ which separates the uniform Fermi liquid from $\sqrt{3} \times \sqrt{3}$ CDW ordered phase.