High pressure Brillouin study of incommensurate rubidium zinc chloride

The pressure dependence of the longitudinal acoustic modes, corresponding to the elastic constants C22 and C33, and the transverse acoustic modes, corresponding to the elastic constants C44 and C66, of Rb2ZnCl4 have been studied using Brillouin scattering. The normal (N) to incommensurate (IC) transition is reflected in the pressure dependence of the C22 and C44 modes. We find that the step in the temperature dependence of the C66 mode at the N-IC transition increases with increasing pressure, indicating a stronger coupling of the corresponding strain to other excitations in the material.