Superfluid $^3$He in Planar Aerogel

TL;DR

This study investigates superfluid $^3$He confined in a novel planar aerogel, revealing phase transitions and magnetic effects that enhance understanding of superfluid behavior in anisotropic nanostructures.

Contribution

It introduces experimental results on superfluid $^3$He in planar aerogel, highlighting the influence of anisotropy and magnetic scattering on superfluid phases.

Findings

Superfluid transition occurs into an equal spin pairing phase.

NMR properties align with the superfluid A phase in anisotropic conditions.

Presence of solid paramagnetic $^3$He affects superfluid properties.

Abstract

We report results of experiments with liquid $^3$He confined in a high porosity anisotropic nanostructure which we call planar aerogel. This aerogel consists of nanofibers (with diameters $\sim10$ nm) which are randomly oriented in the plane normal to the specific axis. We used two samples of planar aerogel prepared using different techniques. We have found that on cooling from the normal phase of $^3$He the superfluid transition in both samples occurs into an equal spin pairing superfluid phase. NMR properties of this phase qualitatively agree with the properties of the superfluid A phase in the anisotropic Larkin-Imry-Ma state. We have observed differences between results obtained in the presence and absence of solid paramagnetic $^3$He on the aerogel strands. We propose that these differences may be due, at least in part, to a magnetic scattering channel which appears in the presence of solid paramagnetic $^3$He.