Isotope effect on photoconductivity in quantum paraelectric SrTiO3

Photoconductivity and various photo-magnetotransport properties have been studied in quantum paraelectric SrTiO3 crystals. (SrTiO3)-O-16 shows giant photoconductivity, as reported before. The photodoped carrier in the O-16 system is of electron type and has high mobility beyond 10(4) cm(2) V-1 s(-1) at 5 K. Its number can reach the order of 10(15) cm(-3). In contrast, isotope-substituted (SrTiO3)-O-18 is not a good photoconductor. In addition, the photocarrier's mobility in the O-18 sample is negligibly small. These results suggest a strong correlation between the quantum fluctuation and the giant photoconductivity in this quantum paraelectric system. In other words, the study of photocarrier dynamics is a novel approach to the investigation of quantum fluctuation in dielectric materials.