Unified character of correlation effects in unconventional Pu-based superconductors and \delta-Pu

TL;DR

This paper investigates the electronic structure of Pu-based superconductors and Pu, revealing a common correlation effect mechanism involving 5f-electron valence states and magnetic fluctuations that influence superconductivity.

Contribution

It provides a unified understanding of correlation effects in Pu superconductors and Pu, highlighting the role of 5f-electron valence fluctuations and magnetic compensation.

Findings

PuCoGa_5 and Pu have complete magnetic moment compensation.

PuCoIn_5 exhibits partial compensation and magnetic ground state.

Superconductivity is likely mediated by magnetic or valence fluctuations depending on the compound.

Abstract

Electronic structure calculations combining the local-density approximation with an exact diagonalization of the Anderson impurity model show an intermediate 5f^5-5f^6-valence ground state and delocalization of the 5f^5 multiplet of the Pu atom 5f-shell in PuCoIn_5, PuCoGa_5, and \delta-Pu. The 5f-local magnetic moment is compensated by a moment formed in the surrounding cloud of conduction electrons. For PuCoGa_5 and \delta-Pu the compensation is complete and the Anderson impurity ground state is a singlet. For PuCoIn_5 the compensation is partial and the Pu ground state is magnetic. We suggest that the unconventional d-wave superconductivity is likely mediated by the 5f-states antiferromagnetic fluctuations in PuCoIn_5, and by valence fluctuations in PuCoGa_5.