Anomalous peak in the superconducting condensate density of cuprate high-T-c superconductors at a unique doping state

The doping dependence of the ratio of the superconducting condensate densit y to the effective mass, n(s)(0)/m(ab)*, was studied in detail by muon-spin rotation for Y0.8Ca0.2Ba2(Cu1-2Zn2)(3)O7-delta and Tl0.5-yPb0.5+ySr2Ca1-xY xCu2O7. Our data show that n(s)(0)/m(ab)* exhibits a peak at a unique dopin g state in the overdoped regime. Its position coincides with the critical d oping state, where the normal state pseudogap was reported to appear and to deplete the electronic density of states, This finding implies that the ps eudogap primarily arises from a change in the electronic ground state rathe r than from thermal fluctuations.