Optical conductivity and x-ray absorption spectra of the Mott-Hubbard compoundsRVO3(R=Sr, Ca, La, and Y)

Abstract

Core-level and valence-band optical spectra provide important information on highly correlated systems. The former corresponds to transitions from the core level to the conduction band, and it is usually related to the unoccupied electronic structure. The later corresponds to transitions from the valence band to the conduction band, and it is sometimes described in terms of the joint density of states. These spectra are usually treated separately due to the differences in the experimental and theoretical methods. We present here a combined description of the core-level and valence-level optical spectra of Mott-Hubbard compounds. In particular, we studied the $\text{O}\text{ }1s$ x-ray absorption and the optical-conductivity spectra of ${\text{SrVO}}_{3}{\text{-CaVO}}_{3}{\text{-LaVO}}_{3}{\text{-YVO}}_{3}$. The experimental data were analyzed using an extended $p\text{\ensuremath{-}}d$ cluster model solved by an exact diagonalization method. The results show that correlation effects alone cannot account for the experimental structures, and that crystal-field effects and exchange interactions are necessary to explain the spectra. We also show that there is a correspondence between the features in the charge-transfer region of both spectra.