Evidence against strong correlation in 4d transition metal oxides, CaRuO3 and SrRuO3

TL;DR

This study shows that 4d transition metal oxides CaRuO3 and SrRuO3 exhibit weak electron correlations, challenging previous assumptions of strong correlations based on similar U/W ratios in 3d systems, and demonstrates that their properties can be explained with first-principles methods.

Contribution

The paper provides evidence that 4d oxides have weak electron correlations, resolving a long-standing debate and showing consistency with first-principles calculations.

Findings

Weak electron correlation strength (U/W ~ 0.2) in CaRuO3 and SrRuO3.

Bulk spectra and properties are well described by first-principles approaches.

Surface and bulk electronic structures differ significantly in these materials.

Abstract

We investigate the electronic structure of 4d transition metal oxides, CaRuO3 and SrRuO3. The analysis of the photoemission spectra reveals significantly weak electron correlation strength (U/W ~ 0.2) as expected in 4d systems and resolves the long standing issue that arose due to the prediction of large U/W similar to 3d-systems. It is shown that the bulk spectra, thermodynamic parameters and optical properties in these systems can consistently be described using first principle approaches. The observation of different surface and bulk electronic structures in these weakly correlated 4d systems is unusual.