Many-body theory for spectra of f-electron systems.

Gunnarsson O., Schonhammer K.

Spectroscopic and thermodynamic properties of some 4f and 5f compounds are studied using the Anderson impurity model. The large degeneracy of the f-level allows one to treat 1/Nf as a small parameter. Exact results are obtained for Nf= infinity and T=0, and even for Nf=1 or 2 accurate results are obtained if corrections of order 1/Nf are included. Comparison with experimental core level photoemission spectra determines the parameters of the model. With these parameters the model has been used to study other electron spectroscopies, such as M4,5 XAS, 4f PES and BIS, for Ce compounds. The model gives a fairly good description of these spectroscopies. The values of the parameters place the known Ce intermetallics in the Kondo limit, where the 4f spectral function has a narrow resonance at the Fermi energy, which has been spectroscopically. This narrow resonance is related to a large density of low-lying excitations, which explains the large low temperature susceptibility and specific heat. The model has also been applied to the 4f photoemission spectra of some Pr and Nd compounds. The agreement with experiment is satisfactory. Finally the model has been used to study the 4f core spectrum of some actinide dioxides. This determines the importance of the hybridization between the 5f state and the O 2p states, and provides an interpretation of a satellite as well as the photon energy dependence of the spectrum close to the 3d to 5f resonance.

Physica Scripta Volume T, 19A 273-81, 1987.

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