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Permanent link (DOI): https://doi.org/10.7939/R34G9B

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Shear modulus of solid 4He confined in aerogel Open Access

Descriptions

Other title
Subject/Keyword
Solid helium
Order-disorder models
Solid helium -- Density -- Measurement
Superfluidity
Aerogels
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Rabbani, Arif
Supervisor and department
Beamish, John (Physics)
Examining committee member and department
Schmitt, Doug (Physics)
Freeman, Mark (Physics)
Adeeb, Samer (Civil and Environmental Engineering)
Department
Department of Physics
Specialization

Date accepted
2011-01-31T16:58:36Z
Graduation date
2011-06
Degree
Master of Science
Degree level
Master's
Abstract
Torsional oscillator experiments on solid 4He show supersolid behavior which appears to be associated with disorder. However, confining helium in the pores of an aerogel does not enhance the supersolid decoupling, even though x-ray measurements confirm that the crystals are highly disordered. Solid helium’s shear modulus also shows anomalous behavior below 150 mK, stiffening as mobile dislocations are pinned by 3He impurities at low temperatures. A highly porous material should also provide effective pinning sites for dislocations. We have made shear modulus measurements on solid 4He grown in a 95% porosity aerogel. We see large modulus decreases as the samples are warmed but at much higher temperatures and over a broader range than in bulk 4He. The frequency dependence of the modulus and dissipation are consistent with a thermally activated process. The activation energies are roughly 10 to 15 K and may be associated with vacancy motion.
Language
English
DOI
doi:10.7939/R34G9B
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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