Orbital Degeneracy, Orbital Polarization and X-ray Absorption Linear Dichroism in Transition-Metal Oxides

Abstract

On the basis of exact diagonalization of a single-ion Hamiltonian, we calculate Mn and Ti L 2,3 x-ray absorption linear dichroism (XLD) spectra for manganites with trivalent Mn ion and YTiO 3 , where antiferro-orbital ordering among the degenerate e g and t 2 g states, respectively, are reported. For the orbital polarization given by a superposition of the doubly degenerate e g states, the superposition is shown to be reflected in the integrated XLD intensity, while not in XLD spectral shape. In the case of the triply degenerate t 2 g states, on the other hand, the superposition is shown to be reflected in both the integrated intensity and the spectral shape. In both e g and t 2 g systems, XLD is shown to be a promising method in identifying orbital polarization.