New gap equation for strongly correlated metals

Assuming a phenomenological self-energy Im Sigma(omega) similar to \omega\( beta), (beta=1), which becomes gapped below T-c, we derived a new gap equat ion. The new gap equation contains the effect of the kinetic energy gain up on developing a superconducting order parameter. However, this new kinetic energy gain mechanism works only for a repulsive pairing potential leading to a s-wave state. In this case, compared to the usual potential energy gai n in the superconducting state as in the BCS gap equation, the kinetic ener gy gain is more effective to easily achieve a high critical temperature T-c since it is naturally Fermi energy scale. In view of the experimental evid ences of a d-wave pairing state in the hole-doped copper-oxide high-T-c sup erconductors, we discuss the implications of our results. (C) 1999 Elsevier Science B.V. All rights reserved.