Strong carrier-scattering in iron-pnictide superconductors LnFeAsO1-y (Ln=La and Nd) obtained from charge transport experiments

Characteristic normal-state charge transport is found in the oxygen-deficient iron-arsenides LnFeAsO(1-y) (Ln: La and Nd) with the highest T-c's among known Fe-based superconductors. The effect of doping in this system is mainly on the carrier scattering, quite distinct from that in high-T-c cuprates. In the superconducting regime of the La system with maximum T-c=28 K, the low-temperature resistivity is dominated by a T-2 term. On the other hand, in the Nd system with T-c higher than 40 K, the carriers are subject to stronger scattering showing T-linear resistivity and small magnetoresistance. Such strong scattering appears crucial for high-T-c superconductivity in the iron-based system.