Experimental study of multilayer solid epitaxy: two-dimensional critical behavior of a quantum solid/superfluid interface

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:7019372

Ramesh, S

This thesis constitutes the first precise, quantitative experimental study of layering transitions, two-dimensional critical temperatures, and their relation to surface roughening. The experiments used superfluid fourth sound to probe the liquid solid /sup 4/He interface, by coupling with surface waves unique to this interface. An annular resonator with electric transducers was used to measure the fourth sound velocity c/sub 4/ in an exfoliated graphite (Grafoil) superleak. Measurements of the pressure dependence of the fourth sound resonance frequencies (and attenuation) from approx.6 bar to approx.26 bar were made along eight isotherms from 1.0 K to 1.7 K. Plots of fourth sound resonance frequency versus coverage clearly indicate layer-by-layer solid nucleation and epitaxal growth of hcp solid /sup 4/He on the basal plane of graphite. Further analysis yielded solid adsorption isotherms and a kinetic growth coefficient for the /sup 4/He crystal surface and also indicated the existence of a critical temperature region and also indicated the existence of a critical temperature region around 1.0-1.2 K (the region of a bulk roughening transition). The acoustical theory for the experimental system was worked out using a parallel waveguide model; Landau's thermohydrodynamic equations were reformulated by including the mass- and heat-exchange effects occurring in the system; the equations were solved to obtain expressions for the velocity of sound propagation and attenuation.

• Research Organization: Pennsylvania State Univ., University Park (USA)
• OSTI ID: 7019372
• Country of Publication: United States
• Language: English

Related Subjects

640450* -- Fluid Physics-- Superfluidity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ADSORPTION ISOTHERMS
EPITAXY
EVEN-EVEN NUCLEI
FLUIDS
FOURTH SOUND
HELIUM 4
HELIUM ISOTOPES
INTERFACES
ISOTHERMS
ISOTOPES
LAYERS
LIGHT NUCLEI
LIQUIDS
MEASURING METHODS
NUCLEI
SOLIDS
STABLE ISOTOPES
SUPERFLUIDITY
VELOCITY