BEC-BCS Crossover in Neutron Matter with Renormalization Group based Effective Interactions

Abstract

We study pure neutron matter in the BEC-BCS crossover regime using renormalization group based low-momentum interactions within the Nozi\`eres-Schmitt-Rink framework. This is an attempt to go beyond the mean field description for low-density matter. We work in the basis of so-called Weinberg eigenvectors where the operator $G_0V$ is diagonal, which proves to be an excellent choice that allows one to use non-local interactions in a very convenient way. We study the importance of correlations as a function of density. We notice that there is a significant reduction of the BCS critical temperature at low-densities as the neutron matter approaches the unitary limit.Comment: 10 pages and 8 figures, Figs 6 and 7 now includes higher cut-offs, discussion of the cut-off dependence improved, new Summary and Outlook section and new references adde