When Repulsion Creates Pairing: A New Perspective on Unconventional Superconductivity

Abstract

Despite the repulsive Coulomb law and the Pauli statistics that do not favor bound states, attraction between electrons or holes is nevertheless possible in the context of many body interaction and of valley potential landscapes, reminiscent of exotic superconducting materials. In particular, in 1965, Kohn and Luttinger published a note revealing that the dynamical screening of the repulsive Coulomb interaction leads, under certain conditions, to an effective attraction necessary for the formation of Cooper pairs. We propose such a formalism adapted to the cuprates, where the screening arises from the superexchange dynamics of virtual holes in the oxygen orbitals of the $Cu O_2$ plane. Inspired from the Bardeen-Copper-Schrieffer (BCS) theory, we can derive some predictions for the temperature-doping phase diagram (pseudo-gap, strange metal, antiferromagnetism, superconducting, and normal states) in semi-quantitative agreement with observations.