ON A MODEL OF SUPERCONDUCTIVITY REALIZED IN THE METALLIC PHASE OF STRONGLY CORRELATED ELECTRONS REVEALING A FIRST-ORDER PHASE TRANSITION

Abstract

Model of superconductivity in the metallic phase of strongly correlated electrons in a half-filled narrow band forming a paramagnetic spin liquid is presented. A qualitatively new ground state and other eigenstates for the superconducting phase are found. Thermodynamic functions are derived within the Bogolubov method. Analytical formulae for the free energy as well as the gap equation and the equation for the chemical potential are presented. It is shown that the energy gap and the chemical potential are mutually correlated functions which must be simultaneously derived in a self-consistent manner. The gap equation and the equation for the chemical potential are numerically solved. The energy gap is doubly-valued in the subcritical temperature region, however only for the higher values of the gap the superconducting phase is stable. The phase transition between the superconducting and the normal phase is found to be of the first order with a conspicuous discontinuity in the entropy. Moreover it is shown that the derivation of the superconducting specific heat from the thermodynamic potential difference requires to include a chemical potential contribution.