Simulations of topological defects and impurities in superfluid 3He

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.author Hänninen, Risto
dc.date.accessioned 2012-02-10T08:55:47Z
dc.date.available 2012-02-10T08:55:47Z
dc.date.issued 2003-10-03
dc.identifier.isbn 951-22-6606-7
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/2109
dc.description.abstract The less common helium isotope, 3He, becomes superfluid when the temperature falls below 1 mK. Superfluidity is one indication of a condensation into the same quantum mechanical state. For 3He the condensation into a single state occurs by forming Cooper pairs. In the superfluid state 3He is an ideal substance to study a non-conventional p-wave spin-triplet pairing. This dissertation considers theoretically different topological defects that appear in the superfluid state and the effect of impurities. Vortices and solitons are the most common topological defects that appear in superfluid 3He. They may be observed in both A and B phases by using nuclear magnetic resonance (NMR). Here we consider the A phase vortex texture in the presence of a stable A-B phase boundary. As a result two new possible vortex textures were obtained to exist at the A-B boundary. Both of these surface sheet textures differ from the vortex sheet that appears in the bulk A phase. Different dissipation mechanisms are analyzed by calculating the NMR absorption spectrum caused by solitons. The normal-superfluid relaxation causes only line broadening, but the spin diffusion, which results from the inhomogeneous texture, also shifts the soliton peak to higher frequencies. Typically helium is an ultra-pure liquid without any impurities. Experimentally the effect of impurities on the superfluid state can be investigated by using a very porous aerogel. When the empty space inside aerogel is filled with liquid helium, the aerogel strands act as an impurity and scatter the helium quasiparticles. In this thesis the effect of impurities on superfluid 3He is analyzed by using the quasiclassical theory and by considering two simple scattering models. In the homogeneous scattering model the impurities are assumed to be evenly distributed, the assumption that is often used for superconductors. In the inhomogeneous model the impurity density is allowed to depend on location. Using these models the critical temperature, pair amplitude, and superfluid density for 3He are determined numerically. en
dc.format.extent 35, [45]
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher Helsinki University of Technology en
dc.publisher Teknillinen korkeakoulu fi
dc.relation.haspart Hänninen R., Blaauwgeers R., Eltsov V. B., Finne A. P., Krusius M., Thuneberg E. V. and Volovik G. E., 2003. Structure of the surface vortex sheet between two rotating 3He superfluids. Physical Review Letters 90, pages 225301 : 1-4. [article1.pdf] © 2003 American Physical Society. By permission.
dc.relation.haspart Kopu J., Hänninen R. and Thuneberg E. V., 2000. One-dimensional textures and critical velocity in superfluid 3He-A. Physical Review B 62, pages 12374-12380. [article2.pdf] © 2000 American Physical Society. By permission.
dc.relation.haspart Hänninen R. and Thuneberg E. V., 2003. Calculation of NMR properties of solitons in superfluid 3He-A. Physical Review B 68, pages 094504 : 1-11. [article3.pdf] © 2003 American Physical Society. By permission.
dc.relation.haspart Hänninen R., Setälä T. and Thuneberg E. V., 1998. Homogeneous scattering model for impure superfluid 3He. Physica B 255, pages 11-18. [article4.pdf] © 1998 Elsevier Science. By permission.
dc.relation.haspart Hänninen R. and Thuneberg E. V., 2000. Superfluid density for 3He in aerogel assuming inhomogeneous scattering. Physica B 284-288, pages 303-304. [article5.pdf] © 2000 Elsevier Science. By permission.
dc.relation.haspart Hänninen R. and Thuneberg E. V., 2003. Model of inhomogeneous impurity distribution in Fermi superfluids. Physical Review B 67, pages 214507 : 1-11. [article6.pdf] © 2003 American Physical Society. By permission.
dc.subject.other Physics en
dc.title Simulations of topological defects and impurities in superfluid 3He en
dc.type G5 Artikkeliväitöskirja fi
dc.description.version reviewed en
dc.contributor.department Department of Engineering Physics and Mathematics en
dc.contributor.department Teknillisen fysiikan ja matematiikan osasto fi
dc.subject.keyword helium-3 en
dc.subject.keyword superfluidity en
dc.subject.keyword texture en
dc.subject.keyword vortex en
dc.subject.keyword soliton en
dc.subject.keyword impurity en
dc.subject.keyword hydrodynamic theory en
dc.subject.keyword quasiclassical theory en
dc.identifier.urn urn:nbn:fi:tkk-000773
dc.type.dcmitype text en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.type.ontasot Doctoral dissertation (article-based) en
dc.contributor.lab Low Temperature Laboratory en
dc.contributor.lab Kylmälaboratorio fi


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