Raman spectroscopic study of phonon dynamics and structural evolution in BaBiO3

In the present study, we explore the phonon dynamics of barium bismuthate (BaBiO3) in a broad temperature range of 5–300 K using Raman spectroscopy. Thereby, the interaction between lattice vibrations, electronic behavior, and the structural phase transition of BaBiO3 is studied, issues of considerable interest due to the material’s relevance for high-temperature superconductivity. We notice an anomalous change in the phonon spectra induced by the structural phase transition from long-range monoclinic I2/m to P21/n symmetry at approximately 140 K. Local structural fluctuations within the I2/m phase have been identified, which could be linked to the P21/n phase. Additionally, strong polarization-dependent overtone bands were detected, which are linked to pre-resonant laser excitation conditions and pronounced electron–phonon coupling. The spectra further reveal a polarization-dependent electronic background around 2.3 eV (measured at 5 K), influenced by the restructuring of the electronic band structure. Our findings provide fresh perspectives on the electronic and vibrational properties of BaBiO3, highlighting the importance of in-depth spectroscopic studies for a thorough understanding of this material’s intricate physics. This work not only enhances the fundamental knowledge of perovskite oxides but also lays the groundwork for exploring their potential in future technological applications.