High-T_c Superconductivity and Shadow State Formation in YBa_{2}Cu_{3}O_{6+\delta} and Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}

TL;DR

This study explores the normal and superconducting states of YBa2Cu3O6+δ and Bi2Sr2CaCu2O8+δ using Hubbard models, revealing how bilayer interactions enhance shadow states and confirming d-wave symmetry with inter-plane pairing.

Contribution

It provides a detailed theoretical analysis of shadow state formation and inter-layer effects in high-Tc cuprates using advanced Hubbard model techniques.

Findings

Shadow states are enhanced in bilayer systems.

Superconducting order parameter exhibits d_{x^2-y^2} symmetry.

Inter-plane Copper pairing is significant in superconductivity.

Abstract

The normal and superconducting state of YBa_{2}Cu_{3}O_{6+\delta} and Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} are investigated by using the mono- and bilayer Hubbard model within the fluctuation exchange approximation and a proper description of the Fermi surface topology. The inter- and intra-layer interactions, the renormalization of the bilayer splitting and the formation of shadow bands are investigated in detail. Although the shadow states are not visible in the monolayer, we find that the additional correlations in bilayers boost the shadow state intensity and will lead to their observability. In the superconducting state we find a $d_{x^2-y^2}$ symmetry of the order parameter and demonstrate the importance of inter-plane Copper pairing.