Doping dependence of the critical current in Bi2Sr2CaCu2Oy

The doping dependence of the critical current density, $J_{c}$, was measured in a series of high quality c-axis oriented ${\rm Bi_2Sr_2CaCu_2O_{8+\delta}}$ thin films. For each doping level we measured the temperature dependence of $J_{c}$. We find that all samples have the same temperature dependence, but the critical current at zero temperature, $J_{c}(0)$, has a non-trivial doping dependence with a maximum at a unique doping level in the overdoped side of the superconducting dome.