Renormalization of electrons in bilayer cuprate superconductors

Abstract

Cuprate superconductors have a layered structure, and then the physical properties are significantly enriched when two or more two copper-oxide layers are contained in a unit cell. Here the characteristic features of the renormalization of the electrons in the bilayer cuprate superconductors are investigated within the framework of the kinetic-energy driven superconducting mechanism. It is shown that the electron quasiparticle excitation spectrum is split into its bonding and antibonding components due to the presence of the bilayer coupling, with each component that is independent. However, in the underdoped and optimally doped regimes, although the bonding and antibonding electron Fermi surface contours deriving from the bonding and antibonding layers are truncated to form the disconnected bonding and antibonding Fermi arcs, almost all spectral weights in the bonding and antibonding Fermi arcs are reduced to the tips of the bonding and antibonding Fermi arcs, which in this case coincide with the bonding and antibonding hot spots. These hot spots connected by the scattering wave vectors qi construct an octet scattering model, and then the enhancement of the quasiparticle scattering processes with the scattering wave vectors qi is confirmed via the result of the autocorrelation of the electron quasiparticle excitation spectral intensities. Moreover, the peak-dip-hump structure developed in each component of the electron quasiparticle excitation spectrum along the corresponding electron Fermi surface is directly related with the peak structure in the quasiparticle scattering rate except for at around the hot spots, where the peak-dip-hump structure is caused mainly by the pure bilayer coupling. Although the kink in the electron quasiparticle dispersion is present all around the electron Fermi surface, when the momentum moves away from the node to the antinode, the kink energy smoothly decreases, while the dispersion kink becomes more pronounced, and in particular, near the cut close to the antinode, develops into a break separating of the fasting dispersing high-energy part of the electron quasiparticle excitation spectrum from the slower dispersing low-energy part. By comparing with the corresponding results in the single-layer case, the theory also indicates that the characteristic features of the renormalization of the electrons are particularly obvious due to the presence of the bilayer coupling.