Similarities in electronic properties of organic charge-transfer solids and layered cobaltates

TL;DR

This paper compares the electronic properties of layered cobaltates and organic charge-transfer solids, highlighting their similar carrier concentration dependence and the role of the extended Hubbard model in understanding their normal and superconducting states.

Contribution

It reveals the commonality in electronic behavior between cobaltates and organic charge-transfer solids, emphasizing the significance of bandfilling of one-quarter and strong correlations in their superconductivity.

Findings

Both families exhibit similar carrier-concentration dependence in their normal states.

Superconductivity is limited to bandfilling of one-quarter in both materials.

Strong correlations and lattice frustration are key features in related unconventional superconductors.

Abstract

The apparently counterintuitive carrier concentration-dependent electronic properties of layered cobaltates have attracted wide interest. Here we point out that very similar carrier-concentration dependence has previously been noted in strongly correlated quasi-one dimensional (quasi-1D) organic charge-transfer solids. The normal states of both families can be understood, over the entire range of carrier concentration of interest, within the extended Hubbard Hamiltonian with significant intersite Coulomb interaction. As with the charge-transfer solids, superconductivity in the cobaltates appears to be limited to bandfilling of one-quarter. We point out further that there exist other families of correlated superconductors, such as spinels, where too strong correlations, geometric lattice frustration and bandfilling of one-quarter seem to be the essential features of the unconventional superconductors.