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.