Examination of Doping Change by C-axis Current Injection in Bi2Sr2CaCu2O8+y and the Influence on Vortex States

It has recently been found that a large c-axis current injection into a stack of the intrinsic Josephson junctions (IJJs) of Bi2Sr2CaCu2O8+y makes the doping level change reversibly and controllably [Y. Koval et al., Appl. Phys. Lett. 96, (2010) 082507]. This can be one of promising in-situ methods to control superconducting properties, such as superconducting critical temperature Tc of high-Tc superconductors. We re-examined this doping process with changing the number of IJJs in a stack, and studied the influence on the vortex state, especially vortex lattice melting transition. Increase of the melting transition fields was observed by the current injection doping, suggesting the reduction of the anisotropy γ (=λc/λab). Dependence of the threshold voltage for the current injection doping on the number of IJJs, relaxation of the c-axis resistance in room-temperature undoping process, and the change of the anisotropy were evaluated.