High temperature superfluidity with abnormal fermionic occupancy

Abstract

We examine a Lipkin based two-level pairing model at finite temperature and in the thermodynamic limit. Whereas at T=0 the model exhibits a superconducting ground state for sufficiently high values of the coupling constant, a partially superconducting phase in whichsome of the particles are paired, is found to survive at high temperatures in a special treatment. This phase is a mixture of “abnormally-occupied” eigenstates, which lie at higher energy, of the interactionless model Hamiltonian.