Superfluid 3He in Aerogel

Abstract

Superfluid 3He is an unconventional neutral superfluid in a p-wave state with three different superfluid phases, each identified by a unique set of characteristic broken symmetries and nontrivial topology. Despite natural immunity of 3He from defects and impurity of any kind, it has been found that they can be artificially introduced with high-porosity silica aerogel. Furthermore, it has been shown that this modified quantum liquid becomes a superfluid with remarkably sharp thermodynamic transitions from the normal state and between its various phases. These phases include new superfluid phases that are stabilized by anisotropy from uniform strain imposed on the silica aerogel framework, and they include new phenomena in a new class of anisotropic aerogels consisting of nematically ordered alumina strands. The study of superfluid 3He in the presence of correlated, quenched disorder from aerogel serves as a model for understanding the effect of impurities on the symmetry and topology of unconventional superconductors.