Temperature dependence of the phonon and roton excitations in liquid sup 4 He

Journal Article · Thu Mar 01 00:00:00 EST 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.41.4224· OSTI ID:6965524

Stirling, W G ^[1]; Glyde, H R ^[2]

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1. Department of Physics, School of Physical Science and Engineering, University of Keele, Keele ST5 5BG, United Kingdom (GB) Science and Engineering Research Council, Daresbury Laboratory, Warrington WA4 4AD, United Kingdom (GB)
2. Department of Physics, University of Delaware, Newark, Delaware 19716 (USA)

We report high-precision neutron scattering measurements of the temperature dependence of the phonon and roton excitations in liquid {sup 4}He at saturated vapor pressure in both the superfluid and normal-fluid phases. Two wave vectors were examined in detail: {ital Q}=0.4 A{sup {minus}1} in the phonon region and {ital Q}=1.925 A{sup {minus}1} at the roton minimum. The goal is to understand excitations in Bose liquids by determining the dynamic structure factor {ital S}({ital Q},{omega}) accurately in both phases. At {ital Q}=0.4 A{sup {minus}1} the sharp peak in {ital S}({ital Q},{omega}) broadens with temperature {ital T}, but remains sharp and well defined in the normal phase ({ital T}{gt}{ital T}{sub {lambda}}) up to {ital T}{approx}3 K. The rate of increase of the width of {ital S}({ital Q},{omega}) shows a break at {ital T}{sub {lambda}}, but otherwise {ital S}({ital Q},{omega}) is similar in the two phases and a transition could not be identified through {ital S}({ital Q},{omega}). In contrast at {ital Q}=1.925 A{sup {minus}1}, the sharp component of {ital S}({ital Q},{omega}) disappears at {ital T}{sub {lambda}} and {ital S}({ital Q},{omega}) is very different above and below {ital T}{sub {lambda}}. This behavior is documented and values of the frequencies and linewidths at several temperatures are reported.

• OSTI ID: 6965524
• Journal Information: Physical Review, B: Condensed Matter; (USA), Vol. 41:7; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
HELIUM II
QUASI PARTICLES
EXCITATION
NEUTRON DIFFRACTION
PHONONS
QUANTUM FLUIDS
ROTONS
STRUCTURE FACTORS
TEMPERATURE DEPENDENCE
COHERENT SCATTERING
DIFFRACTION
ENERGY-LEVEL TRANSITIONS
EVEN-EVEN NUCLEI
FLUIDS
HELIUM 4
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
NUCLEI
SCATTERING
STABLE ISOTOPES
640450* - Fluid Physics- Superfluidity