Anomalous zero-point motion inSrTiO3: Results from γ-ray diffraction

Abstract

Bragg scattering of γ radiation at 316.5 keV was used to collect high-resolution structure-factor data sets on ${\mathrm{SrTiO}}_3$ above and below the cubic-to-tetragonal transition temperature $T_c.$ Moderate uniaxial pressure was applied to force a single domain sample in the low-temperature phase. Well below $T_c$ an anomaly in the vibrational amplitudes is found which is a signature of the incipient ferroelectric transition. The magnitude of zero-point motion of the Ti atoms is substantially larger than the predicted static displacement. The oxygen atoms exhibit enhanced vibrations along all Ti-O bonds.