| Автор | K H Andersen |
| Автор | W G Stirling |
| Дата выпуска | 1994-07-25 |
| dc.description | For pt. I see ibid. vol. 6 p. 821, (1994). In a previous paper neutron inelastic scattering results were presented on the temperature dependence of the excitation spectrum of liquid <sup>4</sup>He in the phonon-roton region. This paper discusses these results in the light of different theoretical analysis procedures, namely the Woods-Svensson hypothesis, the multiphonon subtraction due to Miller et al, and the new Glyde-Griffin theory. The Woods-Svensson hypothesis that the scattering can be decomposed into normal and superfluid parts is examined in detail, but is found to be too simple to accurately describe the observed temperature dependence. This model is used, however, to extract one-phonon parameters, as is the simple multiphonon subtraction model. The data of Andersen et al show that S(Q, omega ) does indeed change character at or just below T<sub>lambda </sub>, the effect being particularly marked at the larger wavevectors considered. This behaviour is in agreement with a recent interpretation by Glyde and Griffin, in which the rotons are seen as single-particle excitations, coupled to the density fluctuations through the presence of a finite Bose condensate. The abrupt disappearance from the density fluctuation spectrum of this mode of excitation at T<sub>lambda </sub> gives rise to a sudden change in S(Q, omega ). A parametrization of the Glyde-Griffin model is compared with the data and provides qualitative agreement with the observed temperature dependence. |
| Формат | application.pdf |
| Издатель | Institute of Physics Publishing |
| Название | Collective excitations in liquid <sup>4</sup>He. II. Analysis and comparison with theory |
| Тип | paper |
| DOI | 10.1088/0953-8984/6/30/004 |
| Electronic ISSN | 1361-648X |
| Print ISSN | 0953-8984 |
| Журнал | Journal of Physics: Condensed Matter |
| Том | 6 |
| Первая страница | 5805 |
| Последняя страница | 5822 |
| Аффилиация | K H Andersen; Inst. Laue-Langevin, Grenoble, France |
| Аффилиация | W G Stirling; Inst. Laue-Langevin, Grenoble, France |
| Выпуск | 30 |
