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Persistent URL http://purl.org/net/epubs/work/37175
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Record Id 37175
Title Condensate fraction and atomic kinetic energy of liquid He-3-He-4 mixtures
Abstract We present neutron-scattering measurements of the momentum distribution of liquid He-3-He-4 mixtures. The experiments were performed at wave vectors Q, 26 <= Q <= 29 A(-1), on the MARI time-of-flight spectrometer at the ISIS Facility, Rutherford Appleton Laboratory, a spallation neutron source. Mixtures with He-3 concentrations x between 0 and 20% were investigated both in the superfluid and normal phases. From the data, we extract the Bose-Einstein condensate fraction n(0) and the momentum distributions of He-3 and He-4 atoms. We find that n(0) increases somewhat above the pure He-4 value when He-3 is added; e.g., from n(0)=(7.25 +/- 0.75)% at x=0 to (11 +/- 3)% at x=15-20 %. This agrees with predictions but is less than the only previous measurement. We find a He-4 kinetic energy K-4 for pure He-4 that agrees with previous determinations. K-4 decreases somewhat with increasing He-3 concentration, less than observed previously and found in early calculations but in agreement with a more recent Monte Carlo calculation. The He-3 response is not well reproduced by a Fermi-gas momentum distribution, n(k). Rather an n(k) having a small step height at the Fermi surface and a substantial high-momentum tail characteristic of a strongly interacting Fermi liquid provides a good fit. This n(k) is consistent with calculated n(k). Thus agreement between theory and experiment is obtained comparing n(k) in contrast to earlier findings based on comparing calculated and observed He-3 kinetic energies.
Organisation CCLRC , ISIS , ISIS-MARI
Keywords ISIS 2007
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Language English (EN)
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Journal Article Phys Rev B 74, no. 14 (2006): 144503. doi:10.1103/PhysRevB.74.144503 2006