In globally isotropic aerogel, A-B phase separation of superfluid 3He in radial direction

Abstract

It is observed that the A-like phase and the B-like phase, which are superfluid phases of 3He in high porosity silica aerogel as an impurity, coexist stably [1]. In this coexisting state, we showed by NMR experiments with radial gradient magnetic field that the A-like phase is in the edge part of a cylindrical aerogel and the B-like phase is in the central part of that [2]. It is proposed that the A-like phase might be more stabilized in globally anisotropic aerogel. According to this proportion, the aerogel might be globally anisotropic in edge part. In order to study whether the aerogel is globally anisotropic, we have performed optical birefringence experiment on aerogel samples in the same batch. This optical method is a useful tool to characterize a global anisotropy of aerogel [3]. Then, we found that aerogel samples are not globally anisotropic. Therefore, there are another mechanism for the A-B phase separation in radial direction.