First-principles study of the Kondo physics of a single Pu impurity in a Th host

TL;DR

This study uses first-principles calculations to explore the Kondo effect in a single plutonium impurity within a thorium host, revealing how surface effects influence electronic correlations.

Contribution

It provides the first detailed theoretical analysis of Kondo physics for a Pu impurity in Th, highlighting surface versus bulk differences in electronic structure.

Findings

Kondo resonance peak observed in Pu impurity's local density of states

Surface Pu atoms exhibit narrower Kondo peaks than bulk atoms

Electronic correlations are sensitive to local environment and hybridization

Abstract

Based on its condensed-matter properties, crystal structure, and metallurgy, which includes a phase diagram with six allotropic phases, plutonium is one of the most complicated pure elements in its solid state. Its anomalous properties, which are indicative of a very strongly correlated state, are related to its special position in the periodic table, which is at the boundary between the light actinides that have itinerant 5$f$ electrons and the heavy actinides that have localized 5$f$ electrons. As a foundational study to probe the role of local electronic correlations in Pu, we use the local-density approximation together with a continuous-time quantum Monte Carlo simulation to investigate the electronic structure of a single Pu atom that is either substitutionally embedded in the bulk and or adsorbed on the surface of a Th host. This is a simpler case than the solid phases of Pu metal, which must also include the interactions between Pu 5$f$ electrons on different Pu atoms. For the Pu impurity atom we have found a Kondo resonance peak, which is an important signature of electronic correlations, in the local density of states around the Fermi energy. Furthermore, we show that the peak width of this resonance is narrower for Pu atoms at the surface of Th than for those in the bulk due to a weakened Pu 5$f$-ligand hybridization at the surface.