Superfluid fraction and effective ion mass in the crystalline crust of a neutron star: role of interband response

Nicolas Chamel

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arXiv · 2605.25600

Superfluid fraction and effective ion mass in the crystalline crust of a neutron star: role of interband response

Nicolas Chamel

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Abstract

Neutron superfluidity in the inner crust of a neutron star is further investigated, focusing on the role of the interband response in the superfluid fraction and the effective mass of crustal ions induced by their motion through the superfluid. Calculations are performed within the linear response theory of the self-consistent time-dependent Hartree-Fock-Bogoliubov equations with Skyrme nuclear energy density functionals in the Bardeen-Cooper-Schrieffer approximation. The absence of interband response in previous analyses is clarified. The neutron superfluid density is formally shown to be consistent with the entrainment matrix derived earlier in homogeneous neutron-proton superfluid mixture, thus providing a unified description of entrainment effects in the inner crust and outer core of a neutron star within the same microscopic framework. The relative importance of the intraband and interband responses in different regions of the crust is numerically assessed from three-dimensional band-structure calculations, taking into account quantum zero-point motion of ions about their equilibrium position. The neutron superfluid fraction is found to be enhanced by the interband response, resulting in effective ion masses that remain close to the mass of quantum mechanically bound nucleons for realistic neutron pairing gaps. Results are compared to predictions from classical hydrodynamics with different prescriptions for the permeability of ions to superfluidity.

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astro-ph.HE cond-mat.supr-con nucl-th

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Nicolas Chamel. 2026-05-25. Superfluid fraction and effective ion mass in the crystalline crust of a neutron star: role of interband response. https://arxiv.org/abs/2605.25600

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