Planar Aerogel and Superfluid $^3$He, Structure and Transitions
Abstract
Anisotropic aerogel possesses structure which exhibits a strong influence over the composition and orientation of the order parameter of imbibed superfluid He. Computational studies have identified stretched aerogel with plane-like structures and compressed aerogel with nematic-like structures. Studies of the B phase of superfluid He in stretched aerogel display an enhanced nuclear magnetic susceptibility likely caused by Andreev bound states near plane-like impurity sites. We report further details on the influence of these planar structures on both magnetic and orbital orientation transitions. The orbital orientation transitions appear in both the B and A phases of stretched and compressed aerogels. These transitions result from a crossover of the superfluid coherence length with long and short length scale structure with the coherence length and are consequently magnetic field independent. Additionally, the apparent temperature-independence of the susceptibility of the B phase equal to that of the A phase in stretched aerogel, is in marked contrast with the field dependence of the superfluid A to B phase transition, indicating that it is a near-isentropic transition.
Keywords
Cite
@article{arxiv.2311.00909,
title = {Planar Aerogel and Superfluid $^3$He, Structure and Transitions},
author = {J. W. Scott and M. D. Nguyen and D. Park and W. P. Halperin},
journal= {arXiv preprint arXiv:2311.00909},
year = {2024}
}