Phonon-modulated x-ray absorption in SrTiO3

Abstract: The aim of this work is to predict the influence of phonon modulations (Kozina et al. 2019 [1]) on the x-ray absorption near-edge fine structure of the Ti-L2,3-edge (Yamaguchi et al. 1982 [2], Thole et al. 1985 [3], De Groot 1990 [4]) in cubic SrTiO3. Employing Density Functional Theory in combination with Multiplet Ligand Field Theory (Haverkort et al. 2012 [5], Luder et al. 2017 [6]), previous experimental and theoretical data on the octahedrally symmetric structure are reproduced with good agreement. Phonon modulations with a maximum atomic displacement of 5% of the lattice parameter are shown to cause polarization-dependent changes in the x-ray absorption spectra just within reach of experimental resolution. This is suggested to reflect the strong susceptibility of the electronic structure to collective lattice excitations in SrTiO3.