Photoinduced Dynamics in Pure and Ca-Doped SrTiO3 Studied by Transient Birefringence and Absorption Measurements

• Published in: Journal of the Physical Society of Japan Vol. 80; no. 10; pp. 104605 - 104605-6
• Main Authors: Kohmoto, Toshiro, Koyama, Yuka, Moriyasu, Takeshi, Okamura, Hidekazu, Yamada, Yasuhiro, Tanaka, Koichiro
• Format: Journal Article
• Language: English
• Published: Tokyo The Physical Society of Japan 01-10-2011; Physical Society of Japan
• Subjects: Birefringence (including stress birefringence, flow birefringence, etc.); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Exact sciences and technology; Ferroelectricity and antiferroelectricity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Phase transitions and curie point; Physics; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter; Calcium additions; Lattice distortion; strontium titanate; Doping; Quantum paraelectricity; Photoinduced effect; Excited states; Cluster model; Pump probe spectrometry; Ferroelectric transitions; ferroelectrics; Ultraviolet radiation; Electric field effects; Strontium titanates; Birefringence; Illumination; quantum paraelectrics
• ISSN: 0031-9015; 1347-4073
• DOI: 10.1143/JPSJ.80.104605

The photoinduced dynamics of the lattice deformation and the relaxed excited state in SrTiO 3 is studied by stationary- and transient-birefringence and pump--probe measurements in comparison with the doping-induced ferroelectric lattice deformation in Ca-doped SrTiO 3 . Ca-doped SrTiO 3 is found to exhibit first-order-like structural deformation with a small threshold UV intensity (${\sim}10^{-3}$ mW/mm 2 ), and it is also found to exhibit a shift in the ferroelectric transition temperature under UV illumination. The photoinduced lattice deformation has the same order of magnitude as the ferroelectric lattice deformation, and it is not affected by the electric field. The occupation probability in the relaxed excited state is found to increase significantly at low temperatures. These experimental results suggest that the photoinduced giant dielectric response of SrTiO 3 is consistent with the conductive-region model rather than the ferroelectric cluster model. SrTiO 3 is a peculiar material in which dielectricity of the Maxwell--Wagner type appears in a stoichiometric material only under UV illumination.