FERMION CONDENSATION IN FERMI SYSTEMS WITH STRONGLY REPULSIVE INTERACTION

A new phenomenon, th, fermion condensation in Fermi systems with stron gly repulsive interaction, is analyzed. This phenomenon is shown to oc cur when the necessary stability condition of the normal ground-state quasiparticle distribution n(F)(p) = theta(p - p(F)) is violated and t he rearrangement of this distribution occurs. The presence of the ferm ion condensate means that a fraction of quasiparticles with different momenta p has the same single-particle energy epsilon(p) which is equa l to the chemical potential mu that results in the essential enhanceme nt of the density of states similar to that of a Bose liquid below the critical temperature T(c). The microscopic theory of the evaluation o f the critical point parameters is outlined. It is found that this pha se transition could occur in a low-density electron gas with r(s) = 10 -15. Various properties of the systems with the fermion condensate are investigated within simple solvable models. The superfluid correlatio ns in systems with the fermion condensate are also considered. The gap DELTA in the single-particle excitation spectra of such systems is sh own to have not the usual exponential BCS-smallness.