Strongly paired fermions: Cold atoms and neutron matter

TL;DR

This paper compares cold atom experiments and neutron matter, showing they share similar equations of state and highlighting the effects of finite interaction range on neutron pairing gaps.

Contribution

It provides quantum Monte Carlo calculations of the equation of state and pairing gap for both systems, revealing their similarities and differences at low densities.

Findings

Equations of state for cold atoms and neutron matter are very similar.

Neutron matter pairing gaps are large but suppressed compared to cold atoms.

Finite effective range reduces neutron pairing gaps at low densities.

Abstract

Experiments with cold Fermi atoms can be tuned to probe strongly interacting fluids that are very similar to the low-density neutron matter found in the crusts of neutron stars. In contrast to traditional superfluids and superconductors, matter in this regime is very strongly paired, with gaps of the order of the Fermi energy. We compute the T=0 equation of state and pairing gap for cold atoms and low-density neutron matter as a function of the Fermi momentum times the scattering length. Results of quantum Monte Carlo calculations show that the equations of state are very similar. The neutron matter pairing gap at low densities is found to be very large but, except at the smallest densities, significantly suppressed relative to cold atoms because of the finite effective range in the neutron-neutron interaction.