Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

We have investigated the magnetotransport above the upper critical field (H_c2) in Fe_1.14Te_0.7Se_0.3, Fe_1.02Te_0.61Se_0.39, Fe_1.05Te_0.89Se_0.11, and Fe_1.06Te_0.86S_0.14. The μSR measurements confirm electronic phase separation in Fe_1.06Te_0.86S_0.14, similar to Fe_1+yTe_1−xSe_x. Superconductivity is suppressed in high magnetic fields above 60 T, allowing us to gain insight into the normal-state properties below the zero-field superconducting transition temperature (T_c). We show that the resistivity of Fe_1.14Te_0.7Se_0.3 and Fe_1.02Te_0.61Se_0.39 above H_c2 is metallic as T → 0, just like the normal-state resistivity above T_c. On the other hand, the normal-state resistivity in Fe_1.05Te_0.89Se_0.11 and Fe_1.06Te_0.86S_0.14 is nonmetallic down to lowest temperatures, reflecting the superconductor-insulator transition due to electronic phase separation.