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NMR measurements of the evolution of helium-3 liquid from two dimensions to three dimensions in helium-3-helium-4 mixture films
Abstract
NMR measurements of $\sp3$He- $\sp4$He mixture films adsorbed on a Nuclepore substrate in a 2 Tesla field over 30 $< T <$ 250 mK are reported as a function of $\sp3$He coverage varied over the range 0.011 $<$ $d\sb3$ $<$ 4 layers for each of three $\sp4$He coverages $d\sb4$ = 1.77, 2.14, and 2.91 layers (40, 44, and 54 $\mu$mols/m$\sp2$). The evolution of the liquid $\sp3$He film from 2-D to 3-D behavior as a function of increasing $d\sb3$ is observed by spin-echo measurements of magnetization calibrated by Curie law magnetization at the lowest $\sp3$He coverage. The degenerate magnetization versus $d\sb3$ shows a positive-sloping plateau of increasingly dense 2-D Fermi liquid (2DFL) for $d\sb3$ $<$ 0.6 layers. The plateau is followed by a step-like doubling of magnetization, then by another sloping plateau. The second plateau is interpreted as showing the magnification of a 2-level 2DFL, where each level corresponds to a discrete state for the $\sp3$He in the mixture film. The step in magnetization is preceded by positive $dM/dT$, indicating thermal excitation into the second level. A second step appears faintly at $d\sb3 \approx$ 1.4 layers. For $d\sb3 >$ 2 layers, the magnetization increases with the same slope as would that of bulk liquid $\sp3$He. The step structure is parameterized as a function of $d\sb3$ for each $d\sb4$, and a 2-level 2DFL model is applied to the $d\sb3 <$ 1.4 layer data. The results and relevant theories of Guyer, Krotscheck, and Treiner are discussed. Structure in the relaxation times $T\sb1 \approx$ 1.5 sec, $T\sb2 \approx$ 7 msec occurs at the same $\sp3$He coverages as the steps in magnetization.
Subject Area
Plasma physics|Physics
Recommended Citation
Higley, Robert Hawley, "NMR measurements of the evolution of helium-3 liquid from two dimensions to three dimensions in helium-3-helium-4 mixture films" (1991). Doctoral Dissertations Available from Proquest. AAI9120891.
https://scholarworks.umass.edu/dissertations/AAI9120891