High Temperature Superconductivity in Strongly Correlated Electronic Systems

In this paper we give a selective review of our work on the role of electron correlation in the theory of high temperature superconductivity. The question of how electronic repulsions might give rise to off-diagonal long range order (ODLRO) in high temperature superconductors is currently one of the key questions in the theory of condensed matter. This paper argues that the key to understanding the occurrence of high temperature superconductivity (HTSC) in cuprates is to be found in the Bohm-Pines Hamiltonian modified to include a polarisable dielectric background. The approach uses reduced electronic density matrices and discusses how these can be used to understand whether ODLRO giving rise to superconductivity might arise from a Bohm-Pines type potential which is comprised of a weak long-range attractive tail and a much stronger short-range repulsive Coulomb interaction. This allows time-reversed electron pairs to undergo a superconducting condensation on alternant Cuprate lattices. Thus, a detailed summary is given of the arguments that such interacting electrons can cooperate to produce a superconducting state in which time-reversed pairs of electrons effectively avoid the repulsive hard-core of the inter-electronic Coulomb interaction but reside on average in