Numerical quantification of the vibronic broadening of the SrTiO3 Ti L-edge spectrum

The 2p(5)3d(1) excited state of the Ti4+ ion in SrTiO3 couples to e(g) distortions of the local oxygen cage, leading to a Jahn-Teller vibronic broadening of the excited states. We quantify this contribution to the broadening of the spectral features of the Ti L edge of SrTiO3 by solving a model Hamiltonian, taking parameters for the Hamiltonian from previous first-principles calculations. Evaluation of the model Hamiltonian indicates that vibronic coupling accounts for the majority of the broadening observed for the L-3 edge, but only a minority of the L-2-edge spectral width. The calculations reveal that, with increasing temperature, the spectral features become increasingly asymmetric and the amount of vibronic broadening grows approximately linearly.