Possible explanation for the absence of bilayer splitting in YBCO

TL;DR

This paper investigates the absence of bilayer splitting in YBCO by modeling two strongly correlated planes with dynamical mean-field theory, revealing that interplane coherence is linked to in-plane quasiparticle renormalization.

Contribution

It introduces a model of coupled strongly correlated planes analyzed via dynamical mean-field theory to explain experimental observations in YBCO.

Findings

Interplane coherence scales with in-plane quasiparticle renormalization.

Numerical spectral functions show the effect of interplane hopping.

Results suggest coherence is suppressed with strong correlations.

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.