Pseudogap, quantum phase fluctuations and spectroscopy of HTCS cuprates

Superconducting critical temperatures T-c are calculated as a function of the doping parameter x for generic layered Cu oxide superconductors, within the framework of a 2D-XY model with quantum phase fluctuations. The model accounts for the lower doping threshold observed at x = 0.05, and allows for a simple interpretation of the ''pseudogap'' in terms of condensation of pre-formed pairs. On the other hand, a novel pairing mechanism, based on the 2D confinement of carriers and on the in-plane overscreening of long-range Coulomb repulsion, is proposed. A 2-3 D dimensional crossover which suppresses 2D pairing is considered in the overdoped regime. (C) 1998 Elsevier Science Ltd. All rights reserved.