Quasiparticle and spin excitations for two coupled Hubbard planes and comparison with experiments on bilayer YBa2CU3O6+x

We use the fluctuation-exchange approximation on the real-frequency axis to calculate the quasiparticle self-energies and dynamic spin susceptibilities for the bonding and antibonding bands of two Hubbard planes coupled by interlayer hopping t'. In the normal state we find that for increasing t' (greater than or similar to 0.3t) the interband spin susceptibility chi(-) becomes much larger than the intraband susceptibility chi(+). The (q) over right arrow, omega, and T dependence of Im chi(-) agrees qualitatively with magnetic neutron scattering data on YBa2Cu3O6+x The ratio of the interlayer and intralayer spin-echo decay rates, T-2/T-2*, becomes for t'=0.3t roughly equal to the recent data of nuclear-quadrupole-resonance spin-echo double resonance. The splitting of the renormalized Fermi lines has about the same magnitude as the splitting observed by angle-resolved photoemission spectroscopy. The superconducting transition temperature for d(x2-y2)-wave pairing decreases rapidly as t' increases above t'similar or equal to 0.3t. Our results for the reductions of intraplane magnetic correlations and pairing correlations by interlayer hopping are consistent with results of quantum Monte Carlo simulations.