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Séminaire MCBT

Mardi 13 septembre 2016 à 11h00,
Salle Louis Weil, E424

Orateur : Adib Tavakoli-Ghinani
"Conduction thermique des phonons dans le régime quantique"


The low temperature thermal properties of amorphous solids are known to be markedly different from their crystalline counterparts due to their low energy excitations. These excitations cause an excess of specific heat, and a quasi-quadratic variation of thermal conductivity at very low temperatures. The microscopic nature of these process is poorly understood, but many of these thermal properties has been explained by the Two-Level-Systems (TLS) model. This model assumes single atom or groups of atoms can have two equilibrium states, in which phonons will have a strong scattering. The qualitative and quantitative measurements brought the idea of universality in these properties in glassy materials. It suggests that these properties will be independent of materials or chemical composition, and will rise from the intrinsic aspect of being disorder. Our perspective is to verify the effects of spatial confinement on these universal properties at very low temperature where only the fundamental vibrational states are excited. When the phonon characteristic lengths such as mean free path (MFP) or phonon dominante wavelength become comparable or bigger than dimensions, then the whole properties will be governed by boundaries. We will analyse for very first time the dependency of fundamental localized excitation of glassy state face to lateral confined systems.

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