BEC-BCS crossover in neutron matter with renormalization-group-based effective interactions

We study pure neutron matter in the BEC-BCS crossover regime using renormalization-group-based low-momentum interactions within the Nozieres-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(0)V is diagonal, which proves to be an excellent choice that allows one to use nonlocal 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.