Thermally modulated infrared-reflectivity spectra in ${\mathrm{BaBiO}}_3$ are measured. The observation of an infrared-active vibrational mode at ∼500 ${\mathrm{cm}}^{\mathrm{-}1}$ and an associated electronic excitation at ∼1.4 eV is consistent with the conjecture of self-localized polarons. However, the estimated polaron mass is anomalously small, suggesting that oscillator strength has transferred from the optical phonons to the infrared-active vibrational mode.

• Received 10 December 1990

DOI:https://doi.org/10.1103/PhysRevB.43.8617