Orientation of the Angular Momentum in Superfluid 3He-A in a Stretched Aerogel

TL;DR

This study investigates the orientation of orbital angular momentum in superfluid 3He-A within a stretched aerogel, confirming theoretical predictions about its alignment due to anisotropy and providing experimental insights into its magnetic properties.

Contribution

The paper experimentally determines the orientation of the orbital angular momentum in superfluid 3He-A in a stretched aerogel, confirming the axial state alignment predicted by Sauls.

Findings

Orbital angular momentum l aligns parallel to the strain axis in the axial state.

Equal spin pairing state (ESP) persists down to the lowest temperatures.

Experimental results support Sauls' theoretical model over Volovik's prediction.

Abstract

Superfluid 3He-A in a fully characterized stretched aerogel, used in previous work [1], has been studied for parallel and perpendicular orientations of the magnetic field relative to the anisotropy axis of the aerogel. Consistently, we find that an equal spin pairing state (ESP) is stabilized down to the lowest temperature. From our pulsed NMR frequency shifts as a function of temperature and tip angle, the orientation of the orbital angular momentum l has been determined. The aerogel anisotropy introduced by uniaxial stretching tends to align l in the axial state parallel to the strain axis, confirming the theory proposed by Sauls [2] and contrary to the prediction of Volovik [3] based on an impurity calculation of Rainer and Vuorio [4].