Pseudogap in elemental plutonium

On cooling from the melt, plutonium (Pu) undergoes a series of structural transformations accompanied by a ≈ 28% reduction in volume from its δ phase to its α phase at low temperatures. While Pu’s partially filled 5 f -electron shells are known to be involved, their precise role in the transformations has remained unclear. By using calorimetry measurements on α -Pu and gallium-stabilized δ -Pu combined with resonant ultrasound and X-ray scattering data to account for the anomalously large softening of the lattice with temperature, we show here that the difference in electronic entropy between the α and δ phases dominates over the difference in phonon entropy. Rather than finding an electronic specific heat characteristic of broad f -electron bands in α -Pu, as might be expected to occur within a Kondo collapsed phase in analogy with cerium, we find it to be indicative of flatter subbands. An important role played by Pu’s 5 f electrons in the formation of its larger unit cell α phase comprising inequivalent lattice sites and varying bond lengths is therefore suggested.

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Anderson impurity mechanism for a multi-level model in δ-Pu

Muñoz,

Jones

2024

Electron. Struct.

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Electronic correlations and spin-orbit interactions in plutonium create variations in the bonding behavior of each of its allotropes. In δ-Pu, the 5f electrons lie at the tipping point between itinerant and localized behavior which has made the use of mixed-level models successful in describing its mechanical properties. The mechanism for the emergence of a mixed-level model has not yet been understood. We use a series of density functional theory approximations to understand the interactions that create a mixed-level description of δ-Pu which leads to accurate physical properties. With the intersite interactions present in the hybrid functional, we show that a single 5f electron engages in orbital-selective bonding that can be understood with an Anderson impurity picture. The Anderson model gives us a mechanism to understand how the bonding in δ-Pu evolves as a function of the interactions in the material such that we obtain both the accuracy and physics of the multi-level models from ab initio theory.

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Pseudogap in elemental plutonium

Cited by 4 publications

References 57 publications

Thermodynamic evidence for electron correlation-driven flattening of the quasiparticle bands in the high-Tc cuprates

Thermodynamic evidence for electron correlation-driven flattening of the quasiparticle bands in the high-Tc cuprates

Indications of flat bands driving the δ to α volume collapse of plutonium

Anderson impurity mechanism for a multi-level model in δ-Pu

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