ABSTRACT
This chapter begins with a very general Hamiltonian that includes an interlayer Coulomb interaction. It deals with Green’s function formalism to derive the spectral function of the extended tight-binding Hamiltonian for model cuprates. By using many-body equations based on the interlayer Coulomb coupling, the chapter demonstrates that the pseudogap near the saddle point can be numerically accounted for. It shows how to derive the excitonic Coulomb (with attractive part) interaction from Coulomb repulsion among like charges and the Coulomb interaction with the ions. The instability results in the transfer of band electrons from one layer to the other, leaving band holes in the former and extra electrons in the latter. In summary, the logic for interlayer charge transfer is simple and clear: The anisotropic Coulomb repulsion is large, particularly in the interlayer part. To minimize it, electrons tend to segregate on one layer.
