Size effects in sup 3 He films

Thesis/Dissertation · Fri Jan 01 00:00:00 EST 1988

OSTI ID:5041552

Freeman, M R

This thesis addresses two related problems. One is the effect of small geometries on the superfluid phases of {sup 3}He, and the other is the nature of the scattering of {sup 3}He quasiparticles at surfaces. The sample consists of 300 nm-thick films of {sup 3}He created by confining the liquid between closely spaced Mylar sheets. The fluid is probed simultaneously by two methods. Nuclear magnetic resonance monitors the spin dynamics of the system, yielding information with which I identify the superfluid phase. The hydrodynamic response of the fluid is determined from the period and damping of a torsion pendulum which generates oscillatory motion of the substrate. In the normal and superfluid phases alike, this response is strongly dependent on microscopic details of the quasiparticle interactions with the surface. I compare the superfluid measurements to the Ginzburg-Landau model in which the order parameter vanishes at the walls (the so-called diffusive boundary condition). Results for the superfluid transition temperature, the superfluid density and the NMR frequency shift are in good quantitative agreement. Also in accord with theory, I find that the superfluid A phase is stabilized by the walls over a wide range of pressures and temperatures at which the B phase is stable in bulk. In contrast with calculations, however, I do not observe the A-B phase boundary. I find other interesting boundary-related phenomena in the normal phase. For pure {sup 3}He, exchange averaging of the liquid and adsorbed surface layer NMR signals is seen. The torsion pendulum experiments reveal an apparent decrease in the friction between the {sup 3}He and the substrate occurring at the superfluid transition in the surface {sub 4}He layer. This slip signature is used in turn to track the evolution of a {sup 4}He film under {sup 3}He pressure.

• Research Organization: Cornell Univ., Ithaca, NY (USA)
• OSTI ID: 5041552
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
HELIUM 3
SURFACE PROPERTIES
EXPERIMENTAL DATA
MEASURING INSTRUMENTS
MEASURING METHODS
NUCLEAR MAGNETIC RESONANCE
SUPERFLUIDITY
DATA
EVEN-ODD NUCLEI
HELIUM ISOTOPES
INFORMATION
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
RESONANCE
STABLE ISOTOPES
400202* - Isotope Effects
Isotope Exchange
& Isotope Separation
640410 - Fluid Physics- General Fluid Dynamics