Strong correlations enhanced by charge-ordering in highly doped cobaltates

TL;DR

This paper explains the unusual spectral and transport properties of highly doped layered cobaltates through charge ordering, revealing how it modifies electronic structure and enhances correlations, consistent with experimental observations.

Contribution

It introduces a charge-ordering mechanism that accounts for strong correlation effects in cobaltates near the band-insulator limit, supported by a theoretical extended Hubbard model study.

Findings

Charge ordering significantly alters the electronic structure.

The system exhibits high effective mass and strong quasiparticle scattering.

Results align with photoemission experiments.

Abstract

We present an explanation for the puzzling spectral and transport properties of layered cobaltates close to the band-insulator limit, which relies on the key effect of charge ordering. Blocking a significant fraction of the lattice sites deeply modifies the electronic structure in a way that is shown to be quantitatively consistent with photoemission experiments. It also makes the system highly sensitive to interactions (especially to intersite ones), hence accounting for the strong correlations effects observed in this regime, such as the high effective mass and quasiparticle scattering rate. These conclusions are supported by a theoretical study of an extended Hubbard model with a realistic band structure on an effective kagom\`e lattice.