The intrinsic electronic phase diagram of iron-oxypnictide superconductors

TL;DR

This study maps the electronic phase diagram of iron-oxypnictide superconductors, revealing anomalous normal state properties, a transition from pseudogap to Fermi liquid behavior with doping, and correlations between these features and superconductivity.

Contribution

First comprehensive analysis of the intrinsic electronic phase diagram of iron-oxypnictide superconductors based on resistivity data across various doping levels.

Findings

Superconductivity emergence linked to anomalous resistivity behavior.

Transition from pseudogap-like to Fermi liquid behavior with increased doping.

Stronger pseudogap features correlate with enhanced superconductivity.

Abstract

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 LaFeAsO$_{1-x}$F$_x$ and SmFeAsO$_{1-x}$F$_x$ 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 LaFeAsO$_{1-x}$F$_x$ 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 SmFeAsO$_{1-x}$F$_x$ where superconductivity is enhanced and vanish when superconductivity is reduced in the doping region with Fermi liquid-like behavior.