ON THE BOSON-FERMION MODEL OF SUPERCONDUCTIVITY

The existence of pair excitations in a Fermi gas interacting via a sho rt-range attractive potential is investigated. Within the ladder appro ximation to the Bethe-Salpeter equation for the effective two-particle interaction, evidence of pair excitation is found at energies slightl y larger than the chemical potential. The link between those excitatio ns and a boson-fermion model of superconductivity (Phys. Lett. A, 196 (1995) 359) is discussed. In particular it is shown that the charge ca rrier density dependence of the pair excitation (boson) energy, assume d phenomenologically in the boson-fermion model, is consistent with th e properties of the interacting Fermi gas studied. These results give support to the microscopic origin of the phenomenological boson-fermio n model of superconductivity.