Electronic States in Two-Dimensional Triangular Cobalt Oxides: Role of Electronic Correlation

TL;DR

This study investigates the electronic structures of two-dimensional cobalt oxides using advanced computational methods, highlighting the effects of electronic correlations and the impact of water intercalation on superconductivity.

Contribution

The paper provides detailed electronic interaction parameters and compares LDA and LDA+U results, offering insights into the role of correlations and water intercalation in cobalt oxides.

Findings

Density of states at Fermi level decreases significantly with LDA+U.

Estimated Coulomb interaction parameters for different compositions.

Discusses the microscopic mechanism of superconductivity in hydrated cobalt oxides.

Abstract

We obtain the electronic states and structures of two-dimensional cobalt oxides, Na$_{x}$CoO$_{2}$ (x=0, 0.35, 0.5 and 0.75) by utilizing the full-potential linear muffin-tin orbitals (FP-LMTO) methods, from which some essential electronic interaction parameters are estimated: the bare on-site Coulomb interaction of cobalt U$_{dd}$=7.5 eV renormalizes to 5 eV for x=0.35, the $pd$ hybridizations t$_{pd\sigma}$ and t$_{pd\pi}$ are -1.40 and 0.70 eV, respectively. The density of states at E$_{F}$ decreases from 6-7 states/eV in the local density approximation (LDA) to about 1.0 states/eV in the LDA+U scheme. The role of the intercalation of water molecules and the microscopic mechanism of the superconductivity in Na$_{0.35}$CoO$_{2}$$\cdot$mH$_{2}$O is discussed.