1 research outputs found
Thermally triggered phononic gaps in liquids at THz scale
In this paper we present inelastic X-ray scattering experiments in a diamond
anvil cell and molecular dynamic simulations to investigate the behavior of
phononic excitations in liquid Ar. The spectra calculated using molecular
dynamics were found to be in a good agreement with the experimental data.
Furthermore, we observe that, upon temperature increases, a low-frequency
transverse phononic gap emerges while high-frequency propagating modes become
evanescent at the THz scale. The effect of strong localization of a
longitudinal phononic mode in the supercritical phase is observed for the first
time. The evidence for the high-frequency transverse phononic gap due to the
transition from an oscillatory to a ballistic dynamic regimes of motion is
presented and supported by molecular dynamics simulations. This transition
takes place across the Frenkel line thermodynamic limit which demarcates
compressed liquid and non-compressed fluid domains on the phase diagram and is
supported by calculations within the Green-Kubo phenomenological formalism.
These results are crucial to advance the development of novel terahertz thermal
devices, phononic lenses, mirrors, and other THz metamaterials.Comment: 8 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1512.0720