Electronic correlations in the superconductor LaFeAsO0.89F0.11 with low carrier density

The crystal structure and numerous normal and superconducting state properties of layered tetragonal P4 /nmm LaFeAsO, with F doping of 11%, are reported. Resistivity measurements give an onset transition temperature Tc=28.2 K, and low field magnetic susceptibility data indicate bulk superconductivity. In applied magnetic field, analysis of the resistive transition results in a critical field Hc2 30 T and a coherence length GL 35 Å. An upper limit for the electron carrier concentration of 1 1021 cm−3 is inferred from the Hall data just above Tc. Strong electron-electron correlations are suggested from temperature-dependent resistivity, Seebeck coefficient, and thermal conductivity data. Anomalies near Tc are observed in both Seebeck coefficient and thermal conductivity data.