Anisotropic aerogels for studying superfluid He-3

Abstract

It may be possible to stabilize new superfluid phases of He-3 with anisotropic silica aerogels. We discuss two methods that introduce anisotropy in the aerogel on length scales relevant to superfluid He-3. First, anisotropy can be induced with uniaxial strain. A second method generates anisotropy during the growth and drying stages. We have grown cylindrical similar to 98% aerogels with anisotropy indicated by preferential radial shrinkage after supercritical drying and find that this shrinkage correlates with small angle x-ray scattering (SAXS). The growth-induced anisotropy was found to be similar to 90 degrees out of phase relative to that induced by strain. This has implications for the possible stabilization of superfluid phases with specific symmetry.