Combining semi-local exchange with dynamical mean-field theory: electronic structure and optical response of rare-earth sesquioxides

Abstract

In rare-earth semiconductors, wide ligand $p$ and rare-earth 5$d$ bands coexist with localized, partially filled 4$f$ shells. A simultaneous description for both extended and localized states represents a significant challenge for first-principles theories. Here, we combine an {\it ab initio} dynamical mean-field theory approach to strong local correlations with a perturbative application of the semi-local modified Becke-Johnson exchange potential to correct the semiconducting gap. We apply this method to calculate the electronic structure and optical response of the light rare-earth sesquioxides RE${}_2$O${}_3$ (RE= La, Ce, Pr and Nd). Our calculations correctly capture a non-trivial evolution of the optical gap in RE${}_2$O${}_3$ due to a progressive lowering of the 4$f$ states along the series and their multiplet structure. 2$p$ $-$ 4$f$ hybridization is found to induce a substantial upward shift for the occupied 4$f$ states occurring within the $p-d$ gap, thus reducing the magnitude of the optical gap. We show that a characteristic plateau observed in the optical conductivity in the Pr and Nd sequioxides right above their absorption edge is a fingerprint of 4$f$ states located within the $p-d$ gap.

9 pages, 4 figures

References in corpus (6)

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Cited by in corpus (3)

• Electronic structure of rare-earth mononitrides: quasiatomic excitations and semiconducting bands
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• Relation between crystal structure and optical properties in the correlated blue pigment YIn${}_{1-x}$Mn${}_x$O${}_3$