A systematic solution of a general model for Copper-Oxides reveals a line of transitions T=Tp(x) for x, the doping away from half-filling less than a critical value, to a phase with broken time reversal and rotational symmetry but with translational symmetry preserved. The single-particle spectrum in this phase is calculated to have a gap of dx2−y2 symmetry. The properties in this phase are compared to the properties of the so called ''pseudo-gap phase'' in the Copper-Oxides. The fluctuations towards this phase promote superconductivity which is either of the dx2−y2 or the generalised s-symmetry depending on whether the projected density of states at the chemical potential is larger in the dx2−y2 channel, as in the hole-doped copper-oxides, or in the s-wave channel.
Cite
@article{arxiv.cond-mat/9905100,
title = {Pseudo-Gap Phase, the Quantum-Critical Point and superconductivity in Copper-Oxide Metals},
author = {C. M. Varma},
journal= {arXiv preprint arXiv:cond-mat/9905100},
year = {2009}
}