Optical Study of the Electronic Structure and Correlation Effects in K0.49RhO2

TL;DR

This study investigates the optical properties of K0.49RhO2, revealing larger crystal-field splitting and a smaller effective mass compared to NaxCoO2, highlighting differences in electronic structure and correlation effects due to Rh 4d orbitals.

Contribution

It provides the first detailed optical analysis of K0.49RhO2, comparing its electronic structure and correlation effects with NaxCoO2, emphasizing the role of Rh 4d orbitals.

Findings

Optical peaks shift to higher energies in K0.49RhO2.

Effective mass in K0.49RhO2 is nearly half that of NaxCoO2.

Larger crystal-field splitting observed in K0.49RhO2.

Abstract

We study the optical properties of the layered rhodium oxide K0.49RhO2, which is isostructural to the thermoelectric material NaxCoO2. The optical conductivity shows broad interband transition peaks as well as a low-energy Drude-like upturn, reminiscent of the optical spectra of NaxCoO2. We find that the peaks clearly shift to higher energies with respect to those of NaxCoO2, indicating a larger crystal-field splitting between eg and t2g bands in K0.49RhO2. The Drude weights suggest that the effective mass of K0.49RhO2 is almost two times smaller than that of NaxCoO2. These differences in electronic structures and correlation effects between NaxCoO2 and K0.49RhO2 are discussed in terms of the difference between Co 3d and Rh 4d orbitals.