Elastic Anomalies in the Quantum Paraelectric Regime of SrTiO ₃

Abstract

Following the proposal by Muller, Berlinger and Tosatti on a possible coherent quantum regime in SrTiO3 below 40 K we have performed elastic measurements to look for possible related anomalies in a near-monodomain crystal. The known anomalies related to the 105 K structural transition were well reproduced. In addition, distinct anomalies were observed below 40 K, both in internal friction and in elastic compliance. The anomalies cannot be explained by phonon interaction with the soft TO mode. A different kind of excitation seems to be required. The features found bear some qualitative resemblance to what is observed in the superfluid phase of 4He.