Possible explanation for the absence of bilayer splitting in YBCO

Abstract

It has been claimed that the absence of the bilayer splitting in the high-temperature superconductor YBCO is a strong experimental indication that there are no coherent quasiparticles present in the CuO planes. We study a pair of strongly correlated planes which are connected by a hopping transfer integral $t_{\perp}$ in the limit of large in-plane coordination number. The effect of the correlation is incorporated in a dynamical mean-field theory, where the Weiss field is determined by a two-site Hubbard Hamiltonian. We have solved this problem by numerical techniques and present results for the spectral function $\rho$ for relevant parameters of the model. For small $t_{\perp}$ we find the coherent hoping between planes to be proportional to the in-plane quasiparticle renormalisation.