The dispersion of [sup 3]He quasiparticles in He II from neutron scattering

Journal Article · Fri Oct 01 04:00:00 EDT 1993 · Journal of Low Temperature Physics; (United States)

DOI:https://doi.org/10.1007/BF00682281· OSTI ID:5538886

Scherm, R; Guckelsberger, K ^[1]; Szprynger, A ^[2]; Fak, B ^[3]

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1. Phys.-Tech, Bundesanstalt, Braunschweig (Germany)
2. W. Trzebiatowski Institute of Low Temperature and Structure Research, Wroclaw (Poland)
3. CENG, Grenoble-Cedex (France)

In an inelastic neutron scattering (INS) experiment on [sup 3]He-[sup 4]He mixtures one observes, besides the photon-roton mode which is barely modified by the admixture of [sup 3]He, an additional excitation at lower energies which is interpreted as quasi-particle-hole excitations of a nearly free Fermi gas. The authors reanalyse INS data of x[sub 3] = 1% and 4.5% mixtures at various pressures to extract the mean energy [cflx [omega]][sub q] of the fermions. In the momentum range 9 < q < 17 nm[sup [minus]1] (above 2k[sub F]) [cflx [omega]][sub q] follows very closely the relation [cflx [omega]][sub q] = A[sub 2]q[sup 2] + A[sub 4]q[sup 4] at all concentrations, pressures and temperatures observed. In a 4.5% mixture (T[sub F] [approximately] 0.3 K), measurements were performed for temperatures in the range 0.07 < T < 0.9 K. They find both A[sub 2] and A[sub 4] to be strongly temperature dependent. For the interpretation of thermodynamical properties, the single particle energy [epsilon][sub k] is parametrized as [epsilon][sub k] = [epsilon][sub 0] + 1/(2m[sup *]) [center dot] k[sub 2] [center dot] (1 + [gamma]k[sup 2]). Neglecting interactions between fermions, they calculate from the free-particle [epsilon][sub k] the scattering function S(q,[omega]) and the mean value of the fermion peak energy [omega][sub q] = [integral] [omega]S[sub 3](q,[omega]) d[omega]/[integral]S[sub 3](q,[omega]) d[omega]. They find that [cflx [omega]][sub q] follows closely [epsilon][sub q], deviating at most by 10%. A comparison to the measured A[sub 2] and A[sub 4] directly yields m[sup *](x[sub 3],p,T) and [gamma](x[sub 3],p,T). In the limit x[sub 3] = 0, p = 0, and T = 0, the density and concentration dependence of the inertial mass is in excellent agreement with values found by Sherlock and Edwards. The temperature dependence of the specific heat data from Greywall and Owers-Bradley et al. are well represented by our model at T<0,5 K.

• OSTI ID: 5538886
• Journal Information: Journal of Low Temperature Physics; (United States), Journal Name: Journal of Low Temperature Physics; (United States) Vol. 93:1-2; ISSN JLTPAC; ISSN 0022-2291
• Country of Publication: United States
• Language: English

Related Subjects

665411* -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BARYON REACTIONS
DISPERSIONS
ENERGY-LEVEL TRANSITIONS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXCITATION
FLUIDS
HADRON REACTIONS
HELIUM 3
HELIUM 4
HELIUM II
HELIUM ISOTOPES
HOLES
INELASTIC SCATTERING
ISOTOPES
LIGHT NUCLEI
MIXTURES
NEUTRON REACTIONS
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
PHYSICAL PROPERTIES
QUANTUM FLUIDS
QUASI PARTICLES
SCATTERING
SPECIFIC HEAT
STABLE ISOTOPES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
THERMODYNAMIC PROPERTIES