Inelastic X-ray Scattering as a Probe of Terahertz Phonon Propagation in Nanoparticle Suspensions

This paper reviews recent inelastic X-ray scattering investigations of simple inhomogeneous materials, such as nanoparticle suspensions in liquids. All studies reported emphasize the ability of immersed nanoparticles to dampen or attenuate acoustic waves through the hosting medium, the effect becoming even more pronounced upon freezing. Additionally, the results show that suspended nanoparticles can cause the onset of non-acoustic modes in the system. Also, the crucial role of Bayesian analysis in guiding spectral line shape modeling and interpretation is discussed. In summary, the presented results demonstrate that the simple inclusion of a sparse amount of nanoparticles profoundly influences sound propagation through a medium. This finding can inspire new avenues in the emerging field of terahertz acoustic steering and manipulation.