Nesting, spin-fluctuations, and odd-gap superconductivity in NaxCoO2 yH2O

TL;DR

This paper investigates the electronic properties of hydrated NaxCoO2, revealing strong nesting and spin-fluctuations that suggest a potential mechanism for odd-gap triplet superconductivity.

Contribution

It provides the first detailed calculation of the one-electron susceptibility in hydrated NaxCoO2, linking nesting and spin-fluctuations to the possibility of odd-gap triplet superconductivity.

Findings

Strong nesting involving 70% of electrons at the Fermi level.

Nesting is robust against doping.

Suggests odd-gap triplet s-wave superconductivity.

Abstract

We have calculated the one-electron susceptibility of hydrated NaxCoO2 and find strong nesting nearly commensurate with a 2X2 superstructure. The nesting involves about 70% of all electrons at the Fermi level and is robust with respect to doping. This nesting creates a tendency to a charge density wave compatible with the charge order often seen at x approx 0.5, which is usually ascribed to electrostatic repulsion of Na ions. In the spin channel, it gives rise to strong spin-fluctuations, which should be important for superconductivity. The superconducting state most compatible with this nesting structure is an odd-gap triplet s-wave state.