Broad Doublet Spectra in the Quantum Paraelectric State of SrTiO₃

Abstract

The 180° light scattering experiment has been performed in SrTiO₃ single crystal under uniaxial stress in order to clarify the physical origin of the Broad Doublet (BD). Especially, the polarization analyses of the BD are made in the stress-induced quantum ferroelectric state (the stress of σ = 19.4 kgf/mm² is applied along the [001]_c direction at T = 16.5 K). The analyses clearly show that the physical origin of the BD is “not” the second sound. The real physical origin of the BD is predicted to be a transverse acoustic mode propagating inside the ferroelectric regions.

Keywords:

• SrTiO₃
• broad doublet
• acoustic mode
• quantum paraelectric state
• stress induced quantum ferroelectric state
• light scattering

Acknowledgments

The authors express their appreciation to Mr. Takao Ohta for his polishing the sample so as to have the optical grade surfaces.

Funding

The present work has been supported in part by a Grant-in-Aid for Scientific Research (C) from the Ministry of Education, Science, Sports and Culture of Japan, No. 22540323.