2006/09/20 by Souleymane Diallo, Diallo, S. O., Jonathan Pearce +9
Physics and Astronomy · #Atomic and Subatomic Physics Research #Cold Atom Physics and Bose-Einstein Condensates #FOS: Physical sciences #Quantum, superfluid, helium dynamics #Statistical Mechanics (cond-mat.stat-mech) #Superconductivity (cond-mat.supr-con) #cond-mat.stat-mech #cond-mat.supr-con
paper · pdf · doi:10.48550/arxiv.cond-mat/0609529
arxiv created 2006/09/20 · openalex publication_date 2006/09/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present neutron scattering measurements of the momentum distribution of liquid 3He-4He mixtures. The experiments were performed at wavevectors Q, 26 ≤ Q ≤ 29 Å-1, on the MARI time-of-flight spectrometer at the ISIS Facility, Rutherford Appleton Laboratory, a spallation neutron source. Mixtures with 3He 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 n0 and the momentum distributions of 3He and 4He atoms. We find that n0 increases somewhat above the pure 4He value when 3He is added; e.g from n0=(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 4He kinetic energy K4 for pure 4He that agrees with previous determinations. K4 decreases somewhat with increasing 3He concentration, less than observed previously and found in early calculations but in agreement with a more recent Monte Carlo calculation. The 3He response is not well reproduced by a Fermi gas momentum distribution, n(\bfk). Rather an n(\bfk) 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(\bfk) is consistent with calculated n(\bfk). Thus agreement between theory and experiment is obtained comparing n(\bfk) in contrast to earlier findings based on comparing calculated and observed 3He kinetic energies.