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Theses

Mesure de la Viscosité dans l'Hélium 3 liquide fortement polarisé

Abstract : 3He at low temperature is a model system for interacting fermions. This thesis is an experimental study of the effect of nuclear polarization on the viscosity of liquid 3He, which is specifically a quantum effect. The same kind of effect has been shown theoretically and experimentally as well in gaseous 3He, but theoretical models disagree on the mechanism in the liquid phase. Experimentally, the main problem is to obtain strongly polarized liquid 3He. The technique used here is the rapid melting of a polarized solid. However, viscosity is strongly temperature dependent. A precise control of the temperature in the experimental cell is then needed to separate polarization effects from thermal effects linked to the rapid melting technique. We show that the viscosity is enhanced by nuclear polarization, in agreement with previous experiments. Thanks to an improved experimental device, our range of polarization extents up to 60\%. Moreover, experiments carried out at different temperatures shows that the polarization induced viscosity enhancement operates beyond the degenerate regime, disappearing only at 1K. Finally, the effect shows a weak pressure dependence. The persistence of an effect from quantum statistical origin beyond the degenerate regime is an open theoretical question. Moreover, we need to improve our understanding of liquid 3He at low temperature, in particular the weak pressure dependence of the polarization induced viscosity enhancement.
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https://tel.archives-ouvertes.fr/tel-00001789
Contributor : Pierre-Etienne Wolf <>
Submitted on : Tuesday, October 8, 2002 - 9:25:47 AM
Last modification on : Friday, December 18, 2020 - 1:34:03 PM
Long-term archiving on: : Friday, April 2, 2010 - 6:30:17 PM

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  • HAL Id : tel-00001789, version 1

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Olivier Buu. Mesure de la Viscosité dans l'Hélium 3 liquide fortement polarisé. Matière Condensée [cond-mat]. Université Joseph-Fourier - Grenoble I, 1998. Français. ⟨tel-00001789⟩

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