2-HOLE QUASI-PARTICLES AND PAIRING IN THE HUBBARD-MODEL OF HIGH-T-C SUPERCONDUCTING CUPRATES

We propose a configuration interaction mechanism that leads to hole pa irs with zero repulsion energy which are exact eigenstates of the two- band Hubbard Hamiltonian. The two-hole pairs have B-1(2)(xy) symmetry and arise from degenerate states at the Fermi level; we show that they must exist independently of the band filling. To discuss the possible relevance of these states to the problem of pairing in high-T-c super conductors we solve five- and nine-site model clusters with four holes . The quasiparticles become dressed by the interaction with the backgr ound holes and get paired with a set of valence band parameters well e stablished for high-T-c cuprates. We predict a number of important exp erimental facts such as binding energies of the correct order of magni tude, the B-1(1)(x(2) - y(2)) symmetry of the order parameter and the singlet-tripler energy separation of the Cooper pairs.