Different carrier compensation effect in La2−xSrxCu0.94Zn0.06O4 and La2−xSrxCu0.94Ni0.06O4 samples

Abstract

The element substitution for Cu is usually used to investigate the mechanism of the high TC superconductivity in cuprates. However, it is still controversial how substitution suppresses superconductivity. We suggest that the suppression of superconductivity by doping is attributed to the local electrons introduced by the dopant regardless of magnetic or nonmagnetic impurities. Here, the compensation effect has been investigated in the bivalent ions doped La2−xSrxCu0.94Zn0.06O4 (LSCZO) and La2−xSrxCu0.94Ni0.06O4 (LSCNO) systems. It is found that the holes introduced by Sr substitution for La have compensated the local electrons and this results in the reappearance of the superconductivity in LSCNO system, while no trace for the superconductivity is observed in LSCZO system. Interestingly, resistivity for LSCZO system decreases faster with doping level compared to that for LSCNO system. This may be ascribed to the fact that the introduced holes do not compensate the local electrons around Zn impurities but participate in the conductive process. We discuss the possible origin of the different compensation effect between LSCNO and LSCZO systems.