Superfluid $^3$He aerogel experiments as a laboratory neutron star analogue

TL;DR

This paper explores superfluid helium-3 aerogel experiments as analogues for neutron star vortex dynamics, revealing regimes of vortex pinning and depinning that could inform astrophysical observations.

Contribution

It introduces a point-vortex simulation in aerogels that models different vortex pinning regimes, providing new insights into neutron star superfluid behavior.

Findings

Vortices depin at high superflow speeds in crust-like aerogels.

Pinned vortices in core-like aerogels are never released, leading to vortex production.

The concepts apply to neutron star physics, potentially transforming observational analysis.

Abstract

Neutron stars make a unique astrophysical test bench for our understanding of quantum physics at kilometre scales. The rotation of a neutron star features glitches, sudden spin-ups that interrupt the otherwise regular stellar spin-down, which are often attributed to the dynamics of pinned quantised vortices in one or several of the superfluid phases inside the star. Laboratory experiments probing superfluid vortices have inspired neutron star theory and simulations from the beginning. Here we argue that vortex experiments in superfluids contained in aerogels show phenomenology that offers a highly appealing but vastly unexplored analogue for neutron star physics. We build a point-vortex simulation that allows analysing experiments in a crust-like and a core-like aerogel, extracting two different regimes of pinned vortex (non-)dynamics and validating a microscopic picture of very strong vortex pinning. In the crust-like aerogel, vortices get depinned once the ambient superflow is fast enough, while in the core-like aerogel pinned vortices are never released and rotational velocity changes are accommodated by the avalanche-like production of new vortices instead. Finally, we show that these concepts should apply also in neutron stars and may thus revolutionise the analysis of neutron star observations.