The distorted axi-planar superfluid phase of $^3$He in the "nematically ordered" aerogel

TL;DR

This paper analyzes the stability of superfluid $^3$He phases in nematically ordered aerogel under uniaxial anisotropy, proposing a new order parameter for the experimentally observed ESP2 phase, which resembles the axi-planar phase.

Contribution

It introduces a phenomenological analysis of superfluid $^3$He phases in anisotropic aerogel and proposes a specific order parameter for the new ESP2 phase observed experimentally.

Findings

Proposed a form of the order parameter for the ESP2 phase.

Suggested that the order parameter approaches that of the axi-planar phase in the weak coupling limit.

Discussed experimental methods to verify the phase identification.

Abstract

Stimulated by the results of NMR experiments with superfluid $^3$He in "nematically ordered" aerogel [1] we report on the results of phenomenological analysis of stability of different phases of superfluid $^3$He subjected to a strong homogeneous uniaxial anisotropy. On a basis of this analysis we suggest a form of the order parameter for the new ESP2 phase observed in the quoted experiments. In the weak coupling limit the suggested order parameter approaches that of the axi-planar phase. We discuss a possible experimental check of the proposed identification of the new phase.