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A Theoretical Investigation of Bound Roton Pairs in Superfluid Helium-4

The Bogoliubov theory of excitations in superfluid helium is used to study collective modes at zero temperature. A repulsive delta function shell potential is used in the quasiparticle excitation energy spectrum to fit the observed elementary excitation spectrum, except in the plateau region. The linearized equation of motion method is used to obtain the secular equation for a collective mode consisting of a linear combination of one and two free quasiparticles of zero total momentum. It is shown that in this case for high-lying collective modes, vertices involving three quasiparticles cancel, and only vertices involving four quasiparticles are important. A decomposition into various angular momentum states is then made. Bound roton pairs in the angular momentum D-state observed in light-scattering experiments exist only for an attractive coupling between helium atoms in this oversimplified model. Thus, the interaction between particles can be reinterpreted as a phenomenological attractive coupling between quasiparticles, in order to explain the Raman scattering from bound roton pairs in superfluid helium.

Identiferoai:union.ndltd.org:unt.edu/info:ark/67531/metadc501017
Date08 1900
CreatorsCheng, Shih-ta
ContributorsKobe, Donald Holm, Sears, Raymond E., Mackey, H. J., McIntyre, Bernard, Krishnan, Raj Muthu
PublisherNorth Texas State University
Source SetsUniversity of North Texas
LanguageEnglish
Detected LanguageEnglish
TypeThesis or Dissertation
Formatvii, 167 leaves: ill., Text
RightsPublic, Cheng, Shih-ta, Copyright, Copyright is held by the author, unless otherwise noted. All rights reserved.

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