Relation between Tc and hole concentration in superconducting cuprates

The superconducting transition temperature, T c, of several series of cuprates shows a nonlinear dependence on the hole concentration, n h, determined by chemical titrations. The t c becomes maximum when n h is in the 0.12-0.15 range in cuprates containing a single Cu-O layer and around 0.2 in cuprates containing two Cu-O layers.