Thermally triggered phononic gaps in liquids at THz scale

In this study 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....

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Bibliographic Details
Published in:Scientific reports 2016-01, Vol.6 (108)
Main Authors: Bolmatov, Dima, Zhernenkov, Mikhail, Zavyalov, Dmitry, Stoupin, Stanislav, Cunsolo, Alessandro, Cai, Yong Q.
Format: Article
Language:English
Subjects:
acoustics
MATERIALS SCIENCE
structure of solids and liquids
thermodynamics
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Summary:In this study 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.
ISSN:2045-2322
2045-2322