The doping phase diagram of Y1-xCaxBa2(Cu1-yZny)3O7-delta from transport measurements: tracking the pseudogap below Tc

The effects of planar hole concentration, p, and magnetic field on the resistivity, rho(T), of high-quality c-axis oriented crystalline thin films and sintered Y1-xCaxBa2(Cu1-yZny)3O7-delta samples were investigated over a wide range of Ca, Zn, and oxygen contents. Zn was used to suppress superconductivity and this enabled us to extract the characteristic pseudogap temperature, T*(p) below Tc0(p) [ = Tc (x =0, y = 0)]. We have also located the characteristic temperature, Tscf, marking the onset of significant superconducting fluctuations above Tc, from the analysis of rho(T,H,p) and rho(T,p) data. This enabled us to identify T*(p) near the optimum doping level where the values of T*(p) and Tscf(p) are very close and hard to distinguish. We again found that T*(p) depends only on the hole concentration p, and not on the level of disorder associated with Zn or Ca substitutions. We conclude that (i) T*(p) (and therefore, the pseudogap) persists below Tc0(p) on the overdoped side and does not merge with the Tc0(p) line and (ii) T*(p) and the pseudogap energy extrapolate to zero at the doping p = 0.19 +/- 0.01.