Density and quasiparticle excitations in liquid sup 4 He

Journal Article · Wed Apr 01 04:00:00 EST 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.45.7321· OSTI ID:7043217

Glyde, H R ^[1]

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1. Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2J1 (Canada)

The recent interpretation of the phonon-roton excitations in superfluid {sup 4}He as a density mode at low wave vector and a quasiparticle excitation at higher {ital Q} proposed by Glyde and Griffin is developed. When there is a condensate, {ital n}{sub 0}({ital T}), the quasiparticle response of liquid {sup 4}He, becomes a component of the observed density dynamic structure factor, {ital S}({ital Q},{omega}). The quasiparticle and density response functions also share a common denominator, due to a coupling via the condensate. At low {ital Q}, the observed {ital S}({ital Q},{omega}) is confined predominantly to a single peak. The peak broadens with temperature but remains well defined in normal {sup 4}He, where {ital n}{sub 0}({ital T})=0. This peak is interpreted as a density mode. At the maxon and higher {ital Q}, {ital S}({ital Q},{omega}) has a sharp peak plus a broad component. The sharp peak is interpreted as the quasiparticle component of {ital S}({ital Q},{omega}). As {ital T} is increased and {ital n}{sub 0}({ital T}) is decreased, the intensity in the sharp peak is reduced until it vanishes from {ital S}({ital Q},{omega}) at {ital T}{sub {lambda}}. A simple model based on uncoupled quasiparticle and density excitations with coupling via {ital n}{sub 0}({ital T}) is proposed. For simplicity, all model parameters are held independent of {ital T}. By allowing only {ital n}{sub 0}({ital T}) to vary with {ital T}, the temperature dependence of {ital S}({ital Q},{omega}) can be quite accurately reproduced.

• OSTI ID: 7043217
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 45:13; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

665420* -- Superfluidity-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
DENSITY
EVEN-EVEN NUCLEI
HELIUM 4
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
NUCLEI
PHONONS
PHYSICAL PROPERTIES
QUASI PARTICLES
ROTONS
STABLE ISOTOPES
STRUCTURE FACTORS
SUPERFLUIDITY
TEMPERATURE DEPENDENCE