PUB - Publikationen an der Universität Bielefeld

For a bilayer model of the high-T-c cuprates consisting of two coupled Hubbard planes we calculate within the FLEX (fluctuation exchange) approximation the quasiparticle self-energies and dynamic spin susceptibilities. We consider a Fermi surface similar to those of the YBaCuO cuprates, an on-site Coulomb repulsion U = 6 t (where t is the intraplane hopping), and interplane hoppings t' up to t' = 0.7 t. For sufficiently large t' (greater than or similar to 0.3 t) the spin susceptibility chi(-) due to transitions between the bonding and antibonding states becomes much larger than the susceptibility chi(+) for transitions within the same band. The spectral density Im chi(-)(q,omega) exhibits a peak centered at the antiferromagnetic wavevector q = Q = (pi, pi) and at the antiparamagnon frequency omega = omega(sf). For decreasing temperature T and increasing t' the peak becomes more and more pronounced. We calculate the Fermi lines of the bonding and antibonding bands for different t'. The superconducting transition temperature T-c for d(x2-y2)-wave pairing decreases as t' increases. Our results are in qualitative agreement with magnetic neutron scattering, magnetic resonance, and photoemission experiments on bilayer YBaCuO cuprates. They are also consistent with the results of quantum Monte Carlo simulations.