ISSN:
1573-7357
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Physik
Notizen:
Abstract We describe new torsional oscillator experiments on 3 He confined in 98.2% open aerogel. In one, we monitored the superfluid fraction of pure 3 He at T 〈〈 T c while we gradually changed the sample pressure. The resulting change in density alters ξ 0 of the superfluid 3 He relative to the distribution of the length scales (correlations) of silica in the aerogel. We observed a T = 0 normal-to-super fluid transition at a pressure of about 6.5 bar, in marked contrast to the bulk where liquid 3 He is superfluid at all pressures. In the second experiment, we measured the temperature dependence of the 3 He ρ s at a pressure of 21.6 bar with different amounts of 4 He present in the cell. Adding 2-3% 4 He slightly increases both T c and ρ s . We found that for 4 He concentrations between 2% and 34%, the 3 He T c increases by a very small amount. However, ρ s , which for pure 3 He in aerogel at 0.5T c is no more than 11%, falls by another factor of 7. This behavior (constant T c , reduced ρ s ) is similar to that observed in granular superconducting films where the long-range order is controlled by phase coherence between adjacent grains.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1023/A:1022502715336
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