Properties of a quantum vortex in neutron matter

TL;DR

This paper investigates the microscopic properties of quantum vortices in neutron matter relevant to neutron star crusts, using advanced self-consistent calculations to analyze flow, specific heat, and vortex characteristics at various densities and temperatures.

Contribution

It provides the first detailed self-consistent 3D Hartree-Fock-Bogoliubov analysis of neutron vortices, including effective radius, specific heat, and vortex core states in neutron-star crust conditions.

Findings

Vortex effective radius determined for filament model

Specific heat significantly larger with vortices than uniform system

Identification of Andreev states and minigap in vortex cores

Abstract

We have studied systematically microscopic properties of a quantum vortex in neutron matter at finite temperatures and densities corresponding to different layers of the inner crust of a neutron star. To this end and in preparation of future simulations of the vortex dynamics, we have carried out fully self-consistent 3D Hartree-Fock-Bogoliubov calculations, using one of the latest nuclear energy-density functionals from the Brussels-Montreal family, which has been developed specifically for applications to neutron superfluidity in neutron-star crusts. By analyzing the flow around the vortex, we have determined the effective radius relevant for the vortex filament model. We have also calculated the specific heat in the presence of the quantum vortex and have shown that it is substantially larger than for a uniform system at low temperatures. The low temperature limit of the specific heat has been identified as being determined by Andreev states inside the vortex core. We have shown that the specific heat in this limit does not scale linearly with temperature. The typical energy scale associated with Andreev states is defined by the minigap, which we have extracted for various neutron-matter densities. Our results suggest that vortices may be spin-polarized in the crust of magnetars. Finally, we have obtained a lower bound for the specific heat of a collection of vortices with given surface density, taking into account both the contributions from the vortex core states and from the hydrodynamic flow.