Electronic structure of the strongly correlated electron system plutonium hexaboride: A study from single-particle approximations and many-body calculations.

The electronic structure of the strongly correlated electron system plutonium hexaboride is studied by using single-particle approximations and a many-body approach. Imaginary components of impurity Green's functions show that 5f_j=5/2 and 5f_j=7/2 manifolds are in conducting and insulating regimes, respectively. Quasi-particle weights and their ratio suggest that the intermediate coupling mechanism is applicable for Pu 5f electrons, and PuB₆ might be in the orbital-selective localized state. The weighted summation of occupation probabilities yields the interconfiguration fluctuation and average occupation number of 5f electrons n_5f ~ 5.101. The interplay of 5f-5f correlation, spin-orbit coupling, Hund's exchange interaction, many-body transition of 5f configurations, and final state effects might be responsible for the quasiparticle multiplets in electronic spectrum functions. Prominent characters in the density of state, such as the coexistence of atomic multiplet peaks in the vicinity of the Fermi level and broad Hubbard bands in the high-lying regime, suggest that PuB₆ could be identified as a Racah material. Finally, the quasiparticle band structure is also presented.