5f band dispersion in epitaxial films of UO2 [electronic resource].

Published:: Washington, D.C. : United States. Dept. of Energy, 2009.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Additional Creators:: Los Alamos National Laboratory, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information

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Summary:

Polymer-assisted deposition of epitaxial films utilizes lattice pinning to produce films of very high stability and properties identical with bulk crystal. Dispersion of the 5f band is shown for the first time in a actinide Mott insulator system, which suggestes hybridization as a leading process in establishing the electronic structure. Hybrid density functional is succesfully employed to calculate the electronic structure of UO₂ in agreement with experiments. UO₂ continues to be a mysterious and elusive compound in terms of understanding the physical properties of a material. Most actinide oxides, including UO₂ are predicted to be metallic. However, UO₂ is an antiferromagnetic insulator with a relatively large gap of about 2eV. The f orbital charater of the excitations across the gap places UO₂ in a Mott insulator category, but no states at the gap center have ever been measured directly, in spite of intensive efforts. In this work we present the first results of the electronic structure investigation of a epitaxial film of UO₂, where we find even more unexpected properties, like the dispersive nature of 5f bands. We also demonstrate the unexpected, very high stability of the epitaxial film of UO₂. In the lattice-pinning scheme, the crystalline nature of the film is preserved all the way up to the topmost layers even after prolonged exposure to atmospheric conditions. Hybridized, dispersive bands are common in the itinerant uranium compounds. One usually finds hybridization of f-orbitals with conduction band to be quite common in f-electron systems at low temperatures. Such bands may reside in the vicinity of the Fermi level and participate in the construction of the Fermi surface. However, in the insulator like UO₂, one expects a more atomic band nature, where f-bands are relatively flat and shifted away from the Fermi level by the gap energy scale. Precise location of UO₂ on the localization-delocalization axis could be pinned down by measurements of band dispersion.

Report Numbers:

E 1.99:la-ur-09-06320
E 1.99: la-ur-09-6320
la-ur-09-6320
la-ur-09-06320

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Note:

Published through SciTech Connect.
01/01/2009.
"la-ur-09-06320"
" la-ur-09-6320"
Vacuum ISSN 0042-207X; VACUAV FT
Martin, Richard L; Jia, Quanxi; Joyce, John J; Roy, Lindsay E; Durakiewicz, Tomasz.

Funding Information:

AC52-06NA25396

View MARC record | catkey: 14445162