Hybridization and Correlation between f- and d-orbital electrons in a valence fluctuating compound EuNi2P2

TL;DR

This study uses high-resolution photoemission spectroscopy to explore the complex interplay of f- and d-electrons in EuNi2P2, revealing temperature-dependent hybridization effects that influence its heavy fermion and valence fluctuation properties.

Contribution

It provides the first detailed experimental investigation of f-d hybridization and correlation effects in EuNi2P2, highlighting their roles in its electronic behavior beyond existing models.

Findings

Hybridization between Eu 4f and Ni 3d states at low temperatures.

Opposite temperature evolution of spectral functions above and below 110 K.

Deviation from periodic Anderson model predictions at higher temperatures.

Abstract

The interaction between localized f and itinerant conduction electrons is crucial in the electronic properties of heavy fermion and valence fluctuating compounds. Using high-resolution angle-resolved photoemission spectroscopy, we systematically investigate the electronic structure of the archetypical valence fluctuating compound EuNi2P2 that hosts multiple f electrons. At low temperatures, we reveal the hybridization between Eu 4f and Ni 3d states, which contributes to the electron mass enhancement, consistent with the periodic Anderson model. With increasing temperature, interestingly, we observe opposite temperature evolution of electron spectral function above and below the Kondo coherence temperature near 110 K, which is in contrast to the monotonic valence change and beyond the expectation of the periodic Anderson model. We argue that both f-d hybridization and correlation are imperative in the electronic properties of EuNi2P2. Our results shed light on the understanding of novel properties, such as heavy fermion behaviors and valence fluctuation, of rare-earth transition-metal intermetallic compounds with multiple f electrons.