Superconductivity induced by current injection into non-superconducting Bi2Sr2CaCu2O8

Unlike doping by oxygen excess, we are able to change the carrier concentration of Bi2Sr2CaCu2O8+δ (Bi2212) single crystals by carrier injection. The electrons injected along c-axis of Bi2212 are trapped in BiO and SrO layers which increases the hole concentration in CuO layers. This method gives an opportunity to observe the evolution of c-axis transport properties of Bi2212 from the antiferromagnetic state to the superconducting overdoped phase on the same sample. In order to eliminate the contact resistance, we have fabricated double cross-bar crystal stacks on fully oxygen depleted Bi2212 single crystal which was not superconducting above 4.2 K. We have observed that by carrier injection the conductivity can be increased until superconductivity above 4.2 K is reached. Continuing the doping by carrier injection, optimum-doped and even overdoped states were obtained. In the superconducting phase, the critical current density exponentially increases by doping level. At the same time, the variation of the critical temperature with doping shows a well known parabolic behavior. Doping by carrier injection offers an unique opportunity of tuning the properties of high-Tc electronic devices in situ.