A POSSIBLE PAIRING MECHANISM FOR HTSC: TWO-DIMENSIONAL CONFINEMENT AND COULOMB OVER-SCREENING

Abstract

Among all the common properties of HTCS cuprates, we build our model on two of them: their high anisotropy, and their extremely low density of charge carriers. The intra-layer pairing mechanism is provided by the two-dimensional over-screening of Coulomb repulsion.1,2 The c-axis zero point energy restricts this pairing to a low carrier density region. Below a critical density, the system behaves as a two-dimensional confined jellium where the energy gain due to charge pairing is larger than the c-axis localization energy. In the high density region, where the pairing energy cannot compensate the localization energy, the system delocalizes and crosses over to a three-dimensional regime. This competition between binding and confinement energies implies a monotonic decrease of mass anisotropy with doping. Pre-formed pairs which exist below a Mean Field (MF) temperature defined by the binding energy, account for pseudo-gap observations.3,4 The superconducting critical temperature T c is given by the Beresinskii–Kosterlitz–Thouless (BKT) transition of the two-dimensional layer, renormalized by quantum phase fluctuations (QPF).5 QPF account for the metal-insulator transition at very low doping.