The electronic structure of Pu materials is directly tied to the details of the 5f electron bonding and hybridization. In compounds where direct 5f-5f bonding is negligible due to crystal structure and wavefunction overlap, hybridization is the key component for 5f electron influence on electronic properties. We examine two strongly correlated materials, PuCoGa5 and PuO2 that span the range of interesting materials from Mott insulator to heavy fermion superconductor. The synergy between synthesis, spectroscopy and modeling has provided a unique opportunity to explore details of the energy and crystal momentum dependence of Pu compound electronic structure through angle-resolved photoemission on single crystal samples and advanced modeling based on theories beyond density functional theory.

The strength of the 5f electron hybridization may be quantified through dispersion in 5f electron peaks from the angle-resolved photoemission. In the case of PuO2, we see over two eV of dispersion in the hybridized (O 2p - Pu 5f) valence band. For PuCoGa5, the quasiparticle peak at the Fermi energy shows 50 meV or more of dispersion in reciprocal space over a range covering slightly less than half the zone center to zone boundary. We are unable to follow the peak dispersion beyond this point as it crosses above the Fermi energy. These energy dispersions place significant constraints on models, which might be used to describe the electronic structure of these strongly correlated materials. For PuCoGa5, models, which place the 5f electrons in a localized configuration without significant hybridization, would not agree with the experimental results. In the case of PuO2, the dispersion measured in photoemission agrees well with the hybrid functional calculations for PuO2 and further support the increase in hybridization moving from ionic UO2 to covalent PuO2.