Theory of resonant x-ray emission spectra in compounds with localized f electrons

TL;DR

This paper presents a comprehensive theoretical framework for resonant x-ray emission spectroscopy (RXES) in compounds with localized f electrons, utilizing the Anderson impurity model and material-specific calculations, applicable across the entire f series.

Contribution

It introduces a novel theoretical approach based on the Anderson impurity model combined with LDA+DMFT calculations for RXES analysis in f-electron compounds, extending beyond traditional limits.

Findings

The theory applies across the entire f series, not just nearly empty or full shells.

Explicit calculations show hybridization effects significantly impact RXES interpretation.

Comparison with traditional superposition models highlights the importance of hybridization effects.

Abstract

I discuss a theoretical description of the resonant x-ray emission spectroscopy (RXES) that is based on the Anderson impurity model. The parameters entering the model are determined from material-specific LDA+DMFT calculations. The theory is applicable across the whole f series, not only in the limits of nearly empty (La, Ce) or nearly full (Yb) valence f shell. Its performance is illustrated on the pressure-enhanced intermediate valency of elemental praseodymium. The obtained results are compared to the usual interpretation of RXES, which assumes that the spectrum is a superposition of several signals, each corresponding to one configuration of the 4f shell. The present theory simplifies to such superposition only if nearly all effects of hybridization of the 4f shell with the surrounding states are neglected. Although the assumption of negligible hybridization sounds reasonable for lanthanides, the explicit calculations show that it substantially distorts the analysis of the RXES data.