Phase separation in low-density neutron matter

Abstract

Low-density neutron matter has been studied extensively for many decades, with a view to better understanding the properties of neutron-star crusts and neutron-rich nuclei. Neutron matter is beyond experimental control, but in the past decade it has become possible to create systems of fermionic ultracold atomic gases in a regime close to low-density neutron matter. In both these contexts pairing is significant, making simple perturbative approaches impossible to apply and necessitating ab initio microscopic simulations. Atomic experiments have also probed polarized matter. In this work, we study population-imbalanced neutron matter (possibly relevant to magnetars and to density functionals of nuclei) arriving at the lowest-energy configuration to date. For small to intermediate relative fractions the system turns out to be fully normal, while beyond a critical polarization we find phase coexistence between a partially polarized normal neutron gas and a balanced superfluid gas. As in cold atoms, a homogeneous polarized superfluid is close to stability but not stable with respect to phase separation. We also study the dependence of the critical polarization on the density.

7 pages, 3 figures

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Cited by in corpus (9)

• Quantum Monte Carlo Calculations with Chiral Effective Field Theory Interactions
• Superfluidity in nuclear systems and neutron stars
• Symmetry energy, neutron skin, and neutron star radius from chiral effective field theory interactions
• Resummation of in-medium ladder diagrams: s-wave effective range and p-wave interaction
• The neutron polaron as a constraint on nuclear density functionals
• Pairing in Asymmetric Many-Fermion Systems: Functional Renormalisation Group Approach
• Fermi polaron in low-density spin-polarized neutron matter
• Neutron matter at the interface(s): static response and effective mass
• The normal state of attractive Fermi gases from coupled-cluster theory