metadata only access
We investigate the effect of Ca doping on the electronic transport properties and superconductivity of Pr1−xCaxBa1.8Sr0.2Cu3Oy and Pr1−xCaxSr2Cu2.7Mo0.3Oy systems. It is found that when PrBa2Cu3Oy (Pr123) is in a highly localized state, the Ca doping mainly decreases the 4f-2p hybridized states and thus releases the holes into the CuO2 planes. Whereas when Pr123 is in a less localized state, the Ca doping not only introduces holes into the CuO2 planes, but also induces dramatic charge transfer. Our results suggest that only when the hole concentration in both the CuO chain and the CuO2 planes reaches a proper value, can the superconductivity be restored in the Pr123 system.