Soft phonon and the central peak at the cubic-to-tetragonal phase transition in SrTiO$_3$

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 SrTiO$_3$.

We compare quantitatively measurements of the soft phonon mode on two differently grown samples and discuss the findings regarding results from thermodynamic 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.