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Correlated disorder in the 3D XY model: a model for 4He in aerogel
2005 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The experimental results from inserting superfluid 4He in aerogel have been surprising. Most porous materials, with porosities down to as low as 30%, generally do not change the scaling properties of 4He at the superfluid phase transition. This is also supported by theoretical work about the nature of the disorder structure in most materials. However, when inserted in silica aerogels of various porosities, the superfluid density exponent is distinctly changed from the undisturbed value of 0.674 to approximately 0.75-0.81. This is surprising as these aerogels are extremely porous, effectively thread-like structures of Silica dioxide making up 0.1-10% of the material, with the rest being incipient voids of air or, in this case, Helium. The reason for the changes in scaling exponents is believed to be that the disorder structure of aerogel is correlated over certain length scales in the material. The scope of this thesis was to investigate a model for correlated aerogel disorder and its scaling properties via Monte Carlo simulations at the phase transition.

Place, publisher, year, edition, pages
2005.
Keyword [en]
Physics Chemistry Maths, statistical mechanics, correlated disorder, 3D XY model, aerogel, percolating clusters
Keyword [sv]
Fysik, Kemi, Matematik
Identifiers
URN: urn:nbn:se:ltu:diva-54642ISRN: LTU-EX--05/202--SELocal ID: b94c1ed9-75ac-44e0-b688-fb0f992a82a2OAI: oai:DiVA.org:ltu-54642DiVA: diva2:1028024
Subject / course
Student thesis, at least 30 credits
Educational program
Engineering Physics, master's level
Examiners
Note
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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CiteExportLink to record
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