Giant photo-induced dielectricity in SrTiO3

Dielectric properties are studied in quantum paraelectric SrTiO3 under UV-light illumination from 100 Hz to 1 MHz at low temperatures. We demonstrate that the complex dielectric constant is strongly enhanced by interband photo-excitation. Dispersion measurements confirm that the photo-induced Debye-type relaxator enhances the dielectric constant. The anomalous temperature and excitation-density dependence of the relaxation time suggests that photo-induced polar domains with finite lifetime lead to the novel dielectric properties.