Momentum distributions in liquid helium

Conference · Fri Jan 01 04:00:00 EST 1988

OSTI ID:6130846

Sokol, P E; Sosnick, T R; Snow, W M

The appearance of the superfluid phase, with its unique macroscopic properties, and the success of the 'two-fluid' model in describing the transport properties are intimately linked to the Bose statistics obeyed by /sup 4/He atoms. The most direct signature of the Bose condensate is in the single particle momentum distribution n(p). In the normal liquid the momentum distribution has a broad Gaussian shape, as predicted for classical systems, with a width determined by the quantum zero point motion. In the superfluid phase a new feature appears, the Bose condensate. The condensate appears as a delta-function singularity in n(p) with an intensity proportional to n/sub 0/, the condensate fraction. There has been extensive experimental work attempting to verify the existence of the condensate. Hohenberg and Platzman originally suggested that inelastic neutron scattering at high momentum transfer Q, where the Impulse Approximation IA can be used to directly relate the observed scattering to n(p), could provide a means of directly observing the condensate. In this review we will concentrate on recent experimental studies that utilize the large flux of high energy neutrons available at spallation neutron sources. These sources, which have become available only recently, have made it possible to make detailed measurements at large enough momentum transfers that the conditions for the Impulse Approximation are approximately satisfied. While deviations from the IA are still present at these higher Q's, they are more amenable to theoretical treatment and detailed predictions are available. Thus, even though no distinct condensate peak is observed, for the first time excellent agreement with the theoretical predictions for n(p) can be obtained. 50 refs., 12 figs.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6130846
• Report Number(s): CONF-8810118-9; ON: DE89014679
• Country of Publication: United States
• Language: English

Related Subjects

640450* -- Fluid Physics-- Superfluidity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COHERENT SCATTERING
DATA
DEEP INELASTIC SCATTERING
DIFFRACTION
DISTRIBUTION FUNCTIONS
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
FLUIDS
FUNCTIONS
HELIUM 4
HELIUM II
HELIUM ISOTOPES
IMPULSE APPROXIMATION
INELASTIC SCATTERING
INFORMATION
INTERACTIONS
ISOTOPES
LANDAU LIQUID HELIUM THEORY
LEPTON-BARYON INTERACTIONS
LEPTON-HADRON INTERACTIONS
LEPTON-NUCLEON INTERACTIONS
LIGHT NUCLEI
LINEAR MOMENTUM
NEUTRON DIFFRACTION
NUCLEI
NUMERICAL DATA
PARTICLE INTERACTIONS
QUANTUM FLUIDS
SCATTERING
STABLE ISOTOPES
SUPERFLUIDITY
TEMPERATURE DEPENDENCE