Sub-THz Raman response and soft phonon in tetragonal BaTiO₃

ABSTRACT

The sub-THz polarized Raman response was measured along the [100] direction in the tetragonal BaTiO₃ single crystal. The soft phonon was detected as a resonance peak for the first time by Raman spectroscopy, thanks to the use of notch filters that suppressed elastic scattering. No relaxation peak was observed and we demonstrated that, contrary to the situation along the ferroelectric c-axis, the soft phonon is sufficient to describe the dielectric response of BaTiO₃ along the a-axis, except in close vicinity of the tetragonal-cubic phase transition.

KEYWORDS:

• Polarized Raman spectroscopy
• structural phase transitions
• BaTiO₃
• soft phonon
• low wavenumber

Acknowledgements

We thank Thomas Kauffmann for his expertise during Raman measurements carried out in the spectroscopy platform of LMOPS.

Disclosure statement

No potential conflict of interest was reported by the author(s).