High Temperature Superconductivity in an Exactly Solvable Model

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 which some of the particles are paired, is found to survive at arbitrarily high temperatures, providing the lowest free energy. Besides, we show explicitly a complete agreement between exact and mean field (BCS) results for intensive mean values in the thermodynamic limit.