UCd$_{11}$: A strongly localized 5$f^3$ material

TL;DR

This study combines DFT+DMFT calculations with PES data to show that UCd$_{11}$ is a highly localized 5$f^3$ uranium system, challenging the idea that satellite features indicate itinerancy.

Contribution

It provides a detailed theoretical analysis demonstrating the localized nature of uranium 5$f$ electrons in UCd$_{11}$, questioning the reliability of satellite features as correlation indicators.

Findings

UCd$_{11}$ exhibits strongly localized 5$f^3$ uranium electrons.

Core-level spectra show satellite features are not definitive indicators of itinerancy.

DFT+DMFT results align with PES data, confirming localization.

Abstract

UCd$_{11}$ is an antiferromagnetic uranium intermetallic compound ($T_{\rm N}$ = 5.3K) with enhanced electron mass and uranium-uranium spacings nearly twice the Hill limit, suggesting a weakly hybridized 5$f$ electronic character. Various x-ray spectroscopy techniques indicate that uranium in UCd$_{11}$ adopts the formal U$^{3+}$ 5$f^3$ configuration, while core-level photoemission spectroscopy (PES) data of UCd$_{11}$ reveal only a weak satellite feature, typically interpreted as a signature of itinerancy. In this work, we present density functional theory (DFT) combined with dynamical mean-field theory (DMFT) calculations of UCd$_{11}$, using material-specific parameters tuned to reproduce valence-band PES spectra at different photon energies, thereby exploiting the energy dependence of photoionization cross sections. Our results demonstrate that UCd$_{11}$ is a highly localized uranium 5$f^3$ system. Furthermore, core-level spectra obtained from a DFT+DMFT Anderson impurity model reveal that, contrary to common assumptions, the presence or absence of satellite structures is not a reliable indicator of strong correlations or itinerant 5$f$ behavior.