DIELECTRIC-SPECTROSCOPY IN SRTIO3

Measurements of the complex dielectric permittivity in nominally pure SrTiO3 are reported for frequencies 10(-3) Hz less-than-or-equal-to nu less-than-or-equal-to 10(8) Hz and temperatures 0.1 K less-than-or-equal-to T-less-than-or-equal-to 300 K. The experiments reveal relaxation phenomena similar to those reported from elastic measurements. The onset of constant loss below 50 K and a low-temperature relaxation reveals characteristic features of a tunneling motion. These phenomena can be interpreted to be characteristic of a quantum phase transition into a coherent quantum state.