Suppression of Tc by Zn impurity in the electron-type LaFe0.925−y Co0.075ZnyAsO system

The effect of non-magnetic Zn impurity on superconductivity in electron-type pnictide superconductor LaFe0.925−yCo0.075ZnyAsO is studied systematically. The optimally doped LaFe0.925Co0.075AsO without Zn impurity exhibits superconductivity at Tcmid of 13.2 K, where Tcmid is defiend as the mid-point in the resistive transition. In the presence of Zn impurity, the superconducting transition temperature, Tcmid, is severely suppressed. The result is consistent with the theoretic prediction on the effect of non-magnetic impurity in the scenario of s± pairing, but it is in sharp contrast to the previous report on the effect of Zn impurity in the F-doped systems. The possible interpretation of the different effects of Zn impurity on superconductivity in different systems is discussed.