Significance of delta in oxygen component of superconductors

[lordgord]

Various chemical formulae for the composition of superconductors quote the oxygen content, ie the number oxygen atoms present, as say Osub(10-delta). I would like to know the significance of delta.

 

[ZapperZ]

Assuming that you are talking about the cuprate superconductors, the oxygen content corresponds to the amount, or fraction, of holes doped into the compound. The holes are what turned the parent, insulating compound into a conductor (or bad metal in this case).

The amount of holes doped is what allows us to categorize the cuprate superconductor family into its phase diagram, from underdopped, optimally-doped, to overdoped.

Zz.