Superfluid fraction in the crystalline crust of a neutron star: role of quantum zero-point motion of ions

TL;DR

This study investigates how quantum zero-point motion affects the superfluid fraction and lattice dynamics in the inner crust of neutron stars using 3D band-structure calculations.

Contribution

It provides a self-consistent analysis of superfluid suppression and ion effective mass increase in neutron star crusts considering quantum effects.

Findings

Superfluid fraction remains strongly suppressed in the inner crust.

Ion effective mass is significantly increased due to quantum zero-point motion.

Crustal dynamics are altered by the presence of superfluid and quantum effects.

Abstract

The suppression of the neutron superfluid fraction in the inner crust of a cold neutron star is mitigated by the quantum zero-point motion of ions about their equilibrium position. In turn, the crustal dynamics is altered by the presence of the neutron superfluid. These effects are studied self-consistently to assess the validity of the usual assumption of a perfect rigid lattice. To this end, fully three-dimensional band-structure calculations of the superfluid fraction are carried out in the weak-coupling approximation, considering body- and face-centered cubic lattices. In both cases, the superfluid fraction is still found to be strongly suppressed in the intermediate region of the inner crust. In turn, the effective mass of the ions is dramatically increased, thus further damping the ion fluctuations. These results are of relevance for the rotational and thermal evolutions of neutron stars.