The continuous displacive phase transition in SrTiO3 near Tc≈105 K features a central elastic peak in neutron scattering investigations at temperatures above Tc, i.e., before the corresponding soft phonon mode is overdamped upon cooling. The origin of this central peak is still not understood. Here, we report an inelastic x-ray scattering investigation of the cubic-to-tetragonal phase transition in SrTiO3. We compare quantitatively measurements of the soft phonon mode on two differently grown samples and discuss the findings regarding results from thermodynamic and transport probes such as specific heat and thermal conductivity. Furthermore, we use inelastic x-ray scattering to perform elastic scans with both high momentum- and milli-electronvolt energy-resolution and, thus, be able to separate elastic intensities of the central peak from low-energy quasielastic phonon scattering. Our results indicate that the evolution of the soft mode is similar in both samples though the intensities of the central peak differ by a factor of four. Measurements revealing anisotropic correlation lengths on cooling towards Tc, indicate that local properties of the crystals to which collective lattice excitations are insensitive are likely at the origin of the central elastic line in SrTiO3.
@article{arxiv.2502.15088,
title = {Soft phonon and the central peak at the cubic-to-tetragonal phase transition in SrTiO$_3$},
author = {Avishek Maity and Klaus Habicht and Michael Merz and Ayman H. Said and Christo Guguschev and Danny Kojda and Britta Ryll and Jan-Ekkehard Hoffmann and Andrea Dittmar and Thomas Keller and Frank Weber},
journal= {arXiv preprint arXiv:2502.15088},
year = {2025}
}