On the metallic conductivity of the delafossites PdCoO2 and PtCoO2

TL;DR

This paper investigates the electronic structure of PdCoO2 and PtCoO2, revealing that their metallic conductivity is mainly due to in-plane d orbitals and that their layered structure causes high anisotropy in conductivity.

Contribution

It provides a detailed electronic structure analysis explaining the quasi-two-dimensional conductivity and weak interlayer coupling in PdCoO2 and PtCoO2.

Findings

Conductivity is mainly due to in-plane Pd and Pt d orbitals.

CoO2 layers act as charge reservoirs with weak interlayer coupling.

Fermi surface is nearly cylindrical, causing high anisotropy.

Abstract

The origin of the quasi two-dimensional behavior of PdCoO2 and PtCoO2 is investigated by means of electronic structure calculations. They are performed using density functional theory in the generalized gradient approximation as well as the new full-potential augmented spherical wave method. We show that the electric conductivity is carried almost exclusively by the in-plane Pd (Pt) d orbitals. In contrast, the insulating CoO2 sandwich layers of octahedrally coordinated Co atoms may be regarded as charge carrier reservoirs. This leads to a weak electronic coupling of the Pd (Pt) layers. The obtained nearly cylindrical Fermi surface causes the strong anisotropy of the electric conductivity.