Hybridization and electron-phonon coupling in ferroelectricBaTiO3probed by resonant inelastic x-ray scattering

Abstract

We investigated the ferroelectric perovskite material ${\mathrm{BaTiO}}_{3}$ by resonant inelastic x-ray scattering (RIXS) at the Ti ${\mathrm{L}}_{3}$ edge. We observe with decreasing temperature a transfer of spectral weight from the elastic to the charge-transfer spectral features, indicative of increasing Ti $3d$-O $2p$ hybridization. When the incident photon energy selects transitions to the Ti $3d\phantom{\rule{4pt}{0ex}}{e}_{g}$ manifold, the quasielastic RIXS response exhibits a tail indicative of phonon excitations. A fit of the spectral line shape by a theoretical model allows us to estimate the electron-phonon coupling strength $M\ensuremath{\sim}0.25$ eV, which places ${\mathrm{BaTiO}}_{3}$ in the intermediate coupling regime.