"Fermion condensation" and the acoustic plasmon induced d-wave superconductivity in the layered cuprate high-T-c compounds

The model for the acoustic plasmon-induced d-wave superconductivity, enhanc ed by the effect of "fermion condensa- tion" in the vicinities of Van Hove saddle points is proposed for the cuprate high-T-c compounds. It is shown t hat the anisotropy of the bare electron spectrum due to the singularities l ying close to the Fermi level support long wavelength collective charge-den sity excitations with acoustic spectrum. These excitations provide attracti on in the d-wave Cooper channel as well as repulsion in the Fock channel in the vicinities of saddle points. The later effect may lead to the fermion condensation and to the self-consistent enhancement of the Cooper attractio n. (C) 2000 Elsevier Science B.V. All rights reserved.