Investigations of solid-liquid interfaces in helium at ultralow temperatures

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Doctoral thesis (article-based)
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Date
2001-06-07
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Language
en
Pages
35, [57]
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Abstract
This Thesis describes ultralow temperature studies of helium quantum crystals. Owing to the surrounding superfluid, small latent heat of crystallization and correspondingly short relaxation times, which are unreachable in ordinary crystals, helium crystals offer a unique and clean modeling system to study surface phenomena in a solid. The measurements of the crystal shape and growth rates are essential in providing the microscopic understanding of crystal growth. Optical observations are probably the most direct way to quantify the surface of crystals. The results presented in this Thesis were obtained with the help of two very powerful experimental techniques that were successfully adopted for ultralow temperature applications: optical interferometry and high-precision pressure measurements. The optical investigations on 3He crystals revealed altogether eleven types of facets at temperatures well below 1 mK, while previously only three facet types have been seen. The growth rates of rough and smooth surface states were explored and show significant anisotropy. The measured growth velocities of different facet types indicate that the main growth mechanism is spiral growth in the regime of suppressed mobility. Important thermodynamic parameters of an interface such as the width of an elementary step and the step free energy were directly deduced from the observed growth kinetics. Results suggest that coupling of the interface to the underlying crystal lattice is relatively "strong" in 3He crystals. Measurements of the spiral growth of the c-facet on 4He crystals in the presence of a small number of 3He atoms were also conducted. They show suppression of the crystal growth velocity with the increase of the 3He atom concentration and indicate "weak" coupling of the interface to the crystal lattice in 4He.
Description
Keywords
interfacial phenomena, solid-liquid interface, helium crystals, morphology, roughening transitions, growth anisotropy, multiple-beam interferometry, phase-shift technique
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Parts
  • J. P. H. Härme, H. Alles, A. Babkin, R. Jochemsen, A. Ya. Parshin, V. Tsepelin, and G. Tvalashvili, Optical Observations of 3He Crystals at mK-Temperatures, Physica B 284-288, 349 (2000).
  • V. Tsepelin, H. Alles, A. Babkin, J. P. H. Härme, R. Jochemsen, A. Ya. Parshin, and G. Tvalashvili, Nucleation and Growth of 3He Crystals below 1 mK, Physica B 284-288, 351 (2000).
  • V. Tsepelin, H. Alles, A. Babkin, J. P. H. Härme, R. Jochemsen, A. Ya. Parshin, and G. Tvalashvili, Direct Observation of (110), (100) and (211) Facets on 3He Crystals, J. Low Temp. Phys. 121, 695 (2000).
  • V. Tsepelin, H. Alles, A. Babkin, J. P. H. Härme, R. Jochemsen, A. Ya. Parshin, and G. Tvalashvili, Observation of Higher Order Facets on 3He Crystals, Phys. Rev. Lett. 86, 1042 (2001).
  • V. Tsepelin, H. Alles, A. Babkin, R. Jochemsen, A. Ya. Parshin, I. Todoshchenko, and G. Tvalashvili, Morphology and Growth Kinetics of 3He Crystals below 1 mK, Report TKK-KYL-006 (2001), to be submitted to J. Low Temp. Phys. [article5.pdf] © 2001 by authors.
  • H. Alles, V. Tsepelin, A. Babkin, R. Jochemsen, A. Ya. Parshin and I. Todoshchenko, Observations on Faceting of 3He Crystals at T = 0.55 mK, accepted for publication in J. Low Temp. Phys. (2001).
  • V. Tsepelin, J. P. Saramäki, A. V. Babkin, P. J. Hakonen, J. J. Hyvönen, R. M. Luusalo, A. Ya. Parshin, and G. K. Tvalashvili, Elementary Steps on the 4He Crystal Interface Probed by 3He Atoms, Phys. Rev. Lett. 83, 4804 (1999).
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Permanent link to this item
https://urn.fi/urn:nbn:fi:tkk-002875