Weak localization in FeSe_1−<i>x</i>Te_<i>x</i>superconducting thin films

Abstract

We have investigated the magneto-resistivity (MR) of FeSe<SUB>1−</SUB><I><SUB>x</SUB></I>Te<I><SUB>x</SUB></I> superconducting films on MgO substrate. The MR of pure FeSe and slightly Te-substituted films demonstrates regular Lorentz-type magnetic field dependence, MR ~ B<SUP>2</SUP>. In highly Te-substituted samples, however, negative MR contribution due to the weak-localization effect gradually dominates at low temperature, which is consistent with the evolution of the temperature dependence of resistivity from a metallic to a weakly semiconductor-like behavior. Furthermore, the negative MR weakens and turns positive as temperature approaches the superconducting transition temperature, which is evidence for the Maki–Thompson correction in the weak-localization regime. The experimental data can be described very well by the weak-localization theory with the existence of scattering by some magnetic moments. The fitting parameters demonstrate that disorder most likely comes from the excess iron.