Reduction of the Superfluid Fraction of ³He in Sintered Silver

Abstract

We have measured the superfluid density of 3He liquid confined within the pores of a silver sinter plug. The silver was of nominal 70 nm size, and was packed to 54% of solid density. The mean pore size as measured was ∼200 nm. The plug was mounted on a torsional oscillator, and the superfluid density can be measured by studying the decrease of the resonant period. We have measured the pressure and temperature dependence of the period shift and find that the superfluid density is suppressed to ∼14% at 0 bar and is ∼53% of its bulk value at 29 bar. There is substantial temperature dependence even at the lowest values of T/T c (∼0.25) achieved in these experiments.

Hysteretic solidification of surfaceHe4measured by the modification of the specularity ofSm1, Jm2 1992Phys. Rev. Lett.Self Cite351150View full textAdd to dashboardCite

“…The 3 He functions as both a hydrostatic medium to generate pressure as well as a detector of specular scattering of 3 He quasiparticles at the surfaces. The 4 He, which is preferentially plated onto the surfaces, serves as the agent to induce specularity as well as the material whose solidification is studied in this experiment.The breaking of superfluid pairs of 3 He by a diffusely scattering surface produces a reduction in superfluid density and transition temperature which were predicted [1,2] and observed in a number of experiments [3][4][5][6][7][8]. Freeman et ai [7] observed that the transition temperature and superfluid fraction were restored to bulk values by the addition of 4 He, as is expected for a specularly scattering surface.…”

“…The superfluid fraction, which is suppressed by confinement, increases with pressure due to the decreasing coherence length. Coating the surfaces with a thin film of 4 He partially restores the suppressed superfluidity, but above 17 bars this effect diminishes as the 4 He film solidifies. This solidification occurs over a range of about 9 bars and is hysteretic.…”

“…This solidification occurs over a range of about 9 bars and is hysteretic. With a slightly thicker 4 He film, solidification occurs at pressures greater than that required for bulk (25 bars).…”

“…PACS numbers: 67.50.Fi, 67.40.Hf This Letter describes a series of experiments on 4 He and 3 He confined within the pores of sintered silver. The 3 He functions as both a hydrostatic medium to generate pressure as well as a detector of specular scattering of 3 He quasiparticles at the surfaces.…”

“…The 3 He functions as both a hydrostatic medium to generate pressure as well as a detector of specular scattering of 3 He quasiparticles at the surfaces. The 4 He, which is preferentially plated onto the surfaces, serves as the agent to induce specularity as well as the material whose solidification is studied in this experiment.…”