The Valence-Fluctuating Ground State of Plutonium

TL;DR

This study uses neutron spectroscopy to reveal that plutonium's ground state involves valence fluctuations between localized and itinerant electrons, resolving longstanding experimental-theoretical discrepancies and advancing understanding of complex electronic correlations.

Contribution

It demonstrates that plutonium's ground state is governed by valence fluctuations, confirming dynamical mean field theory predictions and clarifying its magnetic properties.

Findings

Plutonium exhibits valence fluctuations between electronic configurations.

The ground state is a superposition of localized and itinerant states.

Results reconcile experimental observations with theoretical models.

Abstract

A central issue in material science is to obtain understanding of the electronic correlations that control complex materials. Such electronic correlations frequently arise due to the competition of localized and itinerant electronic degrees of freedom. While the respective limits of well-localized or entirely itinerant ground states are well-understood, the intermediate regime that controls the functional properties of complex materials continues to challenge theoretical understanding. We have used neutron spectroscopy to investigate plutonium, which is a prototypical material at the brink between bonding and non-bonding configurations. Our study reveals that the ground state of plutonium is governed by valence fluctuations, that is, a quantum-mechanical superposition of localized and itinerant electronic configurations as recently predicted by dynamical mean field theory. Our results not only resolve the long-standing controversy between experiment and theory on plutonium's magnetism, but also suggest an improved understanding of the effects of such electronic dichotomy in complex materials.