Broad Doublet and Plasmon Peak in Perovskite-Type Oxides

Abstract

The 180° light scattering experiment has been performed in a Nb-doped SrTi ¹⁶ O ₃ sample. The spectral intensity of a broad doublet (BD) is found to be very weak, supporting the reported hypothesis that a partially softened transverse acoustic mode is the physical origin of the BD. In addition to the BD of weak intensity, two spectral peaks, which do not exist in pure SrTi ¹⁶ O ₃ , are found and assigned to “plasmon-LO phonon coupled modes”. The similar behavior between the BD and the coupled modes is discussed.

Keywords:

• Nb-doped SrTiO₃
• broad doublet
• plasmon
• quantum paraelectrics
• light scattering

Acknowledgments

The authors express their appreciation to Mr. Yasushi Hirata and Mr. Tatsuji Meike for their continual improvement of the sample cell, and Mr. Takao Ohta for his polishing the samples so as to have the optical grade surfaces. he 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. 19540325.