Abstract
The temperature dependence of the dynamic structure factor S(Q, E) for superfluid and normal liquid 4 He at saturated vapor pressure has been measured by inelastic neutron scattering for wave vectors Q between 2.3 and 3.6 Å −1 in the temperature range 0.65<T<3 K. S(Q, E) has three components: A sharp peak at low energies whose dispersion flattens out and whose strength decreases with increasing Q, a broader peak at somewhat higher energies with a stronger dispersion, and a third broad and structureless contribution with a long high-energy tail. The main result is that the first two components disappear at Tλ , while the high-energy contribution broadens toward lower energies. The two-peak structure can be interpreted in terms of a Bose-condensate induced coupling of the two-particle spectrum to the one-particle response, which appears in S(Q, E) in the presence of the Bose condensate. This coupling is analyzed using the hybridization theory of Zawadowski, Ruvalds, and Solana.
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Fåk, B., Bossy, J. Temperature Dependence of S(Q, E) in Liquid 4He Beyond the Roton. Journal of Low Temperature Physics 112, 1–19 (1998). https://doi.org/10.1023/A:1022299227239
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DOI: https://doi.org/10.1023/A:1022299227239