Itinerant-localized crossover and orbital dependent correlations for 4$f$ electrons in cerium-based ternary 122 compounds

TL;DR

This study uses advanced theoretical methods to analyze the electronic structures of cerium-based 122 compounds, revealing an orbital-dependent crossover from itinerant to localized 4f electrons and identifying an unexpected orbital selective insulating state.

Contribution

It introduces a systematic theoretical investigation combining DFT and DMFT to uncover orbital-dependent correlations and a novel insulating state in CeAg2Si2.

Findings

4f electrons become more localized from Ru to Ag

An itinerant-localized crossover driven by chemical pressure

Identification of an orbital selective 4f insulating state in CeAg2Si2

Abstract

The electronic structures of cerium-based ternary 122 compounds Ce$M_{2}$Si$_{2}$, where $M =$ Ru, Rh, Pd, and Ag, are investigated systematically by using the density functional theory in combination with the single-site dynamical mean-field theory. The momentum-resolved spectral functions, total and 4$f$ partial density of states, self-energy functions, and valence state fluctuations are calculated. The obtained results are in good accord with the available experimental data. It is suggested that, upon increasing atomic number from Ru to Ag, the 4$f$ electrons should become increasingly localized. An itinerant-localized crossover for 4$f$ electrons driven by chemical pressure may emerge when $M$ changes from Pd to Ag. Particularly, according to the low-frequency behaviors of 4$f$ self-energy functions, we identify an orbital selective 4$f$ insulating state in CeAg$_{2}$Si$_{2}$, which is totally unexpected.