Fermi systems with long scattering lengths - art. no. 043606

Ground-state energies and superfluid gaps are calculated for degenerate Fer mi systems interacting via long attractive scattering lengths such as cold atomic gases, neutron, and nuclear matter. In the intermediate region of de nsities, where the interparticle spacing (similar to1/k(F)) is longer than the range of the interaction but shorter than the scattering length, the su perfluid gaps and the energy per particle are found to be proportional to t he Fermi energy and thus differ from the dilute and high-density limits. Th e attractive potential increase linearly with the spin-isospin or hyperspin statistical factor such that, e.g., symmetric nuclear matter undergoes spi nodal decomposition and collapses whereas neutron matter and Fermionic atom ic gases with two hyperspin states are mechanically stable in the intermedi ate density region. The regions of spinodal instabilities in the resulting phase diagram are reduced and do not prevent a superfluid transition.