Electronic structure of cerium: A comprehensive first-principles study

TL;DR

This study uses advanced first-principles methods to thoroughly analyze cerium's electronic structure across its allotropes, revealing the correlated nature of 4f electrons and supporting the Kondo volume collapse model for phase transitions.

Contribution

It provides a comprehensive first-principles analysis of cerium's electronic structure, clarifying the behavior of 4f electrons and challenging previous site-selective localization predictions.

Findings

4f electrons are heavily renormalized and correlated in all phases.

The alpha phase exhibits itinerant 4f electrons with strong hybridization.

Results support the Kondo volume collapse scenario for alpha-gamma transition.

Abstract

Cerium, in which the 4$f$ valence electrons live at the brink between localized and itinerant characters, exhibits varying crystal structures and therefore anomalous physical properties with respect to temperature and pressure. Understanding its electronic structure and related lattice properties is one of the central topics in condensed matter theory. In the present work, we employed the state-of-the-art first-principles many-body approach (i.e., the density functional theory in combination with the single-site dynamical mean-field theory) to study its electronic structure thoroughly. The momentum-resolved spectral functions, total and $4f$ partial density of states, optical conductivities, self-energy functions, and atomic eigenstate histograms for cerium's four allotropes under ambient pressure were calculated and analyzed carefully. The calculated results demonstrate that the 4$f$ electrons in the $\alpha$, $\beta$, $\gamma$, and $\delta$ phases are all correlated with heavily remormalized electron masses. In the $\alpha$ phase, the 4$f$ electrons tend to be itinerant, which cause strong hybridization between the 4$f$ and $spd$ bands and remarkable 4$f$ valence state fluctuation. While for the other phases, the 4$f$ electrons are close to be localized. Our calculated results support the Kondo volume collapse scenario for the cerium $\alpha-\gamma$ transition. Finally, we examined the site dependence of $4f$ electronic structure in the $\beta$ phase. The calculated results suggest that it doesn't exhibit a site selective 4$f$ localized state, contrary to previous prediction.