Phases of a fermionic model with chiral condensates and Cooper pairs in   1+1 dimensions
  We study the phase structure of a 4-fermi model with three bare coupling constants, which potentially has three types of bound states. This model is a generalization of the model discussed previously by A. Chodos et al. [Phys. Rev. D 61, 045011 (2000)], which contained both chiral condensates and Cooper pairs. For this generalization we find that there are two independent renormalized coupling constants which determine the phase structure at finite density and temperature. We find that the vacuum can be in one of three distinct phases depending on the value of these two renormalized coupling constants. 
Bogdan Mihaila, Krastan B. Blagoev, and Fred Cooper