Electronic Structure of Copper Oxide Superconductors

In what follows we should bear in mind that the generation of a diamagnetic metallic state (irrespective of whether it is a superconductor or not) will not be favored by a half-filled band of electrons. Either a Peierls distortion or the generation of an antiferromagnetic insulating state will result, with a ferromagnet being less likely for the reasons discussed. Superconductivity in these materials is in fact only observed if electrons are removed, or (less commonly to date) added to the half-filled band. Considerable effort is underway to theoreti- 

System Stability Stability relative to Metallic State 

The electronic properties should depend crucially on the details of the local geometry on this model, via the relative location of the two bands concerned. We see this in the dependence of Tc on 6, which measures the oxygen stoichiometry in the 1-2-3 compound, shown in 

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