Neutron studies of liquid and solid helium: Progress report, May 1, 1987-April 30, 1988

Technical Report · Fri Jan 01 04:00:00 EST 1988

OSTI ID:5120976

Glyde, H R

Liquid and solid helium are prototype simple and solids displaying a wide spectrum of quantum properties. Understanding gained in these simple systems can be readily applied to more complicated materials. Neutron scattering studies carried out at DOE supported national facilities and the associated development of theory and models continue to reveal new physics in these facinating materials. During the past year we have measured the dynamic for factor, S(Q,..omega..), in superfluid and normal liquid /sup 4/He accurately as a function of temperature. This shows that the sharp one-phonon excitation, which exists in the superfluid phase below T/sub lambda/, either disappears at or changes entirely in character at the transition to the normal phase. Thus the sharp one-phonon excitation can be associated with superfluidity (or a condensate). However, we find the weight of scattering in the one-phonon peak, Z(Q,T), is not porportional to the superfluid density, /rho//sub S/(T). We have also measured S(Q,..omega..) in the range 3 less than or equal to Q less than or equal to 15 /angstrom//sup /minus/1/ in order to obtain the width W(Q) and peak position, E(Q), of S(Q,..omega..) as a function of Q. We have made microscopic calculations of S(Q,..omega..) in the range 3 less than or equal to Q less than or equal to 15 /angstrom//sup /minus/1/ in both liquid /sup 3/He and /sup 4/He. The aim is a first principles evaluation of W(Q) and E(Q) as a function of Q for comparsion with experiments.

• Research Organization: Delaware Univ., Newark (USA). Dept. of Physics
• DOE Contract Number: FG02-84ER45082
• OSTI ID: 5120976
• Report Number(s): DOE/ER/45082-4; ON: DE88009096
• Country of Publication: United States
• Language: English

Related Subjects

640450 -- Fluid Physics-- Superfluidity
656003* -- Condensed Matter Physics-- Interactions between Beams & Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COHERENT SCATTERING
DIFFRACTION
DOCUMENT TYPES
ELEMENTS
FLUIDS
FORM FACTORS
GASES
HELIUM
LIQUIDS
MOMENTUM TRANSFER
NEUTRON DIFFRACTION
NONMETALS
ORIENTATION
PARTICLE PROPERTIES
PHONONS
PROGRESS REPORT
QUASI PARTICLES
RARE GASES
RESEARCH PROGRAMS
SCATTERING
SOLIDS
SPIN ORIENTATION
SUPERFLUIDITY
SURFACES
TEMPERATURE DEPENDENCE