Correlation-induced suppression of bilayer splitting in high-T c cuprates: A variational cluster approach

We carry out a theoretical study of the bilayer single-band Hubbard model in the undoped and in the superconducting phases by means of the variational cluster approach. In particular, we focus on the splitting between the "bonding" and "antibonding" bands induced by the interlayer hopping, as well as its interplay with strong correlation effects. We find that the splitting is considerably suppressed in both the normal and superconducting phases, in qualitative agreement with experiments on Bi ₂Sr ₂CaCu ₂O _8+δ. In addition, in the superconducting phase, the shape of the splitting in k space is modified by correlations.