Comparison of impurity effect between two Tc domes in LaFeAsO(1-x)H(x).

Hydrogen-doped LaFeAsO(1-x)H(x) system has a unique 2-dome structure. The effects of Zn impurities on the first and second superconducting domes in LaFe(1-y)Zn(y)AsO(1-x)H(x) (x = 0.10 for the first superconducting phase (SC1) and 0.35 for the second superconducting phase (SC2)) are examined by electrical resistivity, Hall effect and magnetization measurements. Substitution with Zn strongly suppresses the critical temperature (Tc) and behaves as a nonmagnetic impurity. The suppression rates are: 17(4) K/% (SC1) and 6.9(5) K/% (SC2). It was considered that Zn impurities induced Anderson localization, which triggered the disappearance of the superconductivity, but no decisive conclusions on the dominant pairing symmetry for each dome were obtained.