Volume 87, Number 1, July 2009
Article Number 17005
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 23 July 2009
EPL, 87 (2009) 17005
DOI: 10.1209/0295-5075/87/17005

The intrinsic electronic phase diagram of iron-oxypnictide superconductors

C. Hess, A. Kondrat, A. Narduzzo, J. E. Hamann-Borrero, R. Klingeler, J. Werner, G. Behr and B. Büchner

Leibniz-Institute for Solid State and Materials Research, IFW Dresden - 01171 Dresden, Germany, EU

received 22 May 2009; accepted in final form 24 June 2009; published July 2009
published online 23 July 2009

We present the first comprehensive derivation of the intrinsic electronic phase diagram of the iron-oxypnictide superconductors in the normal state based on the analysis of the electrical resistivity $\rho $ of both LaFeAsO1- xFx and SmFeAsO1- xFx for a wide range of doping. Our data give clear-cut evidence for unusual normal-state properties in these new materials. In particular, the emergence of superconductivity at low doping levels is accompanied by distinct anomalous transport behavior in $\rho $ of the normal state which is reminiscent of the spin-density wave (SDW) signature in the parent material. At higher doping levels $\rho $ of LaFeAsO1-xFx shows a clear transition from this pseudogap-like behavior to Fermi-liquid–like behavior, mimicking the phase diagram of the cuprates. Moreover, our data reveal a correlation between the strength of the anomalous features and the stability of the superconducting phase. The pseudogap-like features become stronger in SmFeAsO1-xFx where superconductivity is enhanced and vanish when superconductivity is reduced in the doping region with Fermi-liquid–like behavior.

74.25.Dw - Superconductivity phase diagrams.
74.25.Fy - Transport properties (electric and thermal conductivity, thermoelectric effects, etc.).
71.27.+a - Strongly correlated electron systems; heavy fermions.

© EPLA 2009