Field-theoretical description of the crossover between BCS and BEC in a non-Fermi superconductor Original Research Article

Using the field-theoretical methods we studied the evolution from BCS description of a non-Fermi superconductor to that of Bose–Einstein condensation (BEC) in one loop approximation. We showed that the repulsive interaction between quasi-particles is determined by the exponent α of the Anderson propagator in a 2D model. For α≠0 the crossover is also continuous and for α=0 we obtain the case of the Fermi liquid. We analyzed the weak coupling regime which is characterized by a weak interaction between quasi-particles as well as the strong coupling regime where the interaction potential is strong. Numerical methods were used for studying the intermediate regime. It was also shown that the transition which is driven by the coupling strength can also be induced by the exponent α.