Theory of the optical and magneto-optical spectra of cerium and uranium compounds

The optical and magneto-optical (MO) spectra of cerium and uranium compounds are investigated theoretically, using an energy-band approach in combination with the linear-response formalism. The energy bands are obtained within the local-density approximation (LDA), as well as with its generalization in which explicit on-site Coulomb correlations are included (LDA+U). We find that for CeSb, CeSe, and CeTe the LDA+U approach gives an adequate description of the measured MO spectra. For CeSb we calculate a colossal MO Kerr rotation of about 60 degrees, which is in agreement with recent experiments. For the uranium compounds we find that the LDA gives a good description of the MO spectra, if the 5f-electrons are sufficiently delocalized, as is illustrated by e.g., UAsSe. The MO spectra of the uranium monochalcogenides US, USe, and UTe pose a challenge to present-day correlated band theory: it is shown that for UTe, where the 5f-electrons are quasilocalized, the LDA+U approach gives a reasonable result. For US, and also for USe, a better description is obtained if, as a correction beyond the on-site Coulomb interaction U, a screened hole in the 5f-shell is taken into account.