Condensate fraction and atomic kinetic energy of liquid {sup 3}He-{sup 4}He mixtures

Journal Article · Sun Oct 01 04:00:00 EDT 2006 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.74.144503· OSTI ID:20853757

Diallo, S O; Glyde, H R ^[1]; Pearce, J V ^[1]; Azuah, R T ^[2]; Albergamo, F ^[3]

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1. Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716-2570 (United States)
2. Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-2115 (United States)
3. European Synchrotron Radiation Facility, Boite Postale 220, 38043 Grenoble (France)

We present neutron-scattering measurements of the momentum distribution of liquid {sup 3}He-{sup 4}He mixtures. The experiments were performed at wave vectors Q, 26{<=}Q{<=}29 A {sup -1}, on the MARI time-of-flight spectrometer at the ISIS Facility, Rutherford Appleton Laboratory, a spallation neutron source. Mixtures with {sup 3}He 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{sub 0} and the momentum distributions of {sup 3}He and {sup 4}He atoms. We find that n{sub 0} increases somewhat above the pure {sup 4}He value when {sup 3}He is added; e.g., from n{sub 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 {sup 4}He kinetic energy K{sub 4} for pure {sup 4}He that agrees with previous determinations. K{sub 4} decreases somewhat with increasing {sup 3}He concentration, less than observed previously and found in early calculations but in agreement with a more recent Monte Carlo calculation. The {sup 3}He 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 {sup 3}He kinetic energies.

• OSTI ID: 20853757
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 14 Vol. 74; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ATOMS
BOSE-EINSTEIN CONDENSATION
DISTRIBUTION
FERMI GAS
FERMI LEVEL
HELIUM 3
HELIUM 4
KINETIC ENERGY
LIQUIDS
MIXTURES
MONTE CARLO METHOD
NEUTRON DIFFRACTION
NEUTRON SOURCES
SUPERFLUIDITY
TIME-OF-FLIGHT METHOD
TIME-OF-FLIGHT SPECTROMETERS