Electron Correlations in the Low Carrier Density LaFeAsO0.89F0.11 Superconductor (Tc ~ 28 K)

The crystal structure and numerous normal and superconducting state properties of layered tetragonal (P4/nmm) LaFeAsO comopund with F ~ 11 % doping are reported. Resistivity measurements give an onset transition temperature Tconset = 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 of ~ 35 . An upper limit for the electron carrier concentration of 1 x 10^21 cm-3 is inferred from 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.