Electronic structure and resonant inelastic x-ray scattering in Ca3Ru2O7

TL;DR

This study combines density functional theory and resonant inelastic x-ray scattering to analyze the electronic structure of Ca3Ru2O7, revealing its Mott insulator nature and detailed excitation features at various edges.

Contribution

It provides a comprehensive analysis of Ca3Ru2O7's electronic structure using advanced theoretical calculations and experimental RIXS measurements, highlighting the material's Mott insulating behavior.

Findings

Ca3Ru2O7 is a Mott insulator despite band theory predictions.

RIXS spectra show distinct features corresponding to intra-t2g and t2g to eg transitions.

Differences in spectra at Ca sites are due to core-level width variations.

Abstract

We have investigated the electronic structure of the transition metal oxide Ca3Ru2O7 within density functional theory using the generalized gradient approximation while considering strong Coulomb correlations in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. Ca3Ru2O7 can be classified as a Mott insulator since it was expected to be metallic from band structure calculations. We have investigated the resonant inelastic x-ray scattering spectra at the Ru and Ca K, L3, and M3 edges as well as at the O K edge. The experimentally measured resonance inelastic x-ray spectrum of Ca3Ru2O7 at the Ru L3 edge possesses a sharp feature below 2 electron-volts corresponding to transitions within the Ru t_2g levels. The excitation located from 2 to 4 electron-volts is due to t2g -> e_g transitions. The third wide structure situated at 4.5-11 electron-volts appears due to transitions between the Ru 4dO states derived from the tails of oxygen 2p states and t_2g and e_g states. The measured resonance inelastic x-ray spectra at the Ru L3 and M3 edges are very similar. However, the corresponding measured resonance inelastic x-ray spectra at the Ca site quite differ from each other due to the significant difference in the widths of core-levels.