Collapse of quasiparticle multiplets and 5f itinerant-localized crossovers in cubic phase Pu3Ga

The physical properties of plutonium and plutonium-based intermetallic compounds are extremely sensitive to temperature, pressure, and chemical alloying. A celebrated example is the high-temperature δ phase plutonium, which can be stabilized at room temperature by doping it with a few percent trivalent metal impurities, such as gallium or aluminum. The cubic phase Pu₃Ga, one of the plutonium-gallium intermetallic compounds, plays a key role in understanding the phase stability and phase transformation of the plutonium-gallium system. Its electronic structure might be essential to figure out the underlying mechanism that stabilizes the δ phase plutonium-gallium alloy. In the present work, we studied the temperature-dependent correlated electronic states of cubic phase Pu₃Ga by means of a combination of the density functional theory and the embedded dynamical mean-field theory. We identified orbital selective 5f itinerant-localized (coherent-incoherent) crossovers which could occur upon temperature. Actually, there exist two well-separated electronic coherent temperatures. The higher one is for the 5f5/2 state [Tcoh(5f5/2) ≈ 700 K], while the lower one is for the 5f7/2 state [Tcoh(5f7/2) ≈ 100 K]. In addition, the quasiparticle multiples which originate from the many-body transitions among the 5f⁴, 5f⁵, and 5f⁶ electronic configurations, decay gradually. The hybridizations between the localized 5f bands and conduction bands are subdued by high temperature. Consequently, the Fermi surface topology is changed, which signals a temperature-driven electronic Lifshitz transition. Finally, the calculated linear specific heat coefficient γ is approximately 112 mJ / (mol K²) at $T = 80$ K.