Anomalous transport properties and phase diagram of the FeAs-based SmFeAsO1-xFx superconductors

We report the detailed phase diagram and anomalous transport properties of Fe-based high-T-c superconductors SmFeAsO1-xFx. It is found that superconductivity emerges at x similar to 0.07, and optimal doping takes place in the x similar to 0.20 sample with the highest T-c similar to 54 K. T-c increases monotonically with doping; the anomaly in resistivity from structural phase or spin-density-wave order is rapidly suppressed, suggesting a quantum critical point around x similar to 0.14. As manifestations, a linear temperature dependence of the resistivity shows up at high temperatures in the x < 0.14 regime but at low temperatures just above T-c in the x > 0.14 regime; a drop in carrier density evidenced by a pronounced rise in the Hall coefficient is observed below the temperature of the anomaly peak in resistivity. A scaling behavior is observed between the Hall angle and temperature: cot theta(H)proportional to T-1.5 for all samples with different x in SmFeAsO1-xFx system.