Doping dependence of upper critical field and Hall resistivity in LaFeAsO1-xFx

TL;DR

This study investigates how fluorine doping affects the upper critical field and Hall resistivity in LaFeAsO1-xFx, revealing a monotonic increase in Hc2 with underdoping and evidence of multi-band superconductivity.

Contribution

It provides new insights into the doping dependence of Hc2 and Hall resistivity, highlighting the role of multi-band effects and pseudo-gap phenomena in this material.

Findings

Hc2 increases monotonically with decreasing fluorine doping.

Hc2 exceeds 75 T at x=0.05, showing a dome-shaped Tc dependence.

Hall resistivity exhibits non-linear field dependence in non-superconducting samples.

Abstract

The electrical resistivity (Rxx) and Hall resistivity (Rxy) of LaFeAsO1-xFx have been measured over a wide fluorine doping range 0 =< x =< 0.14 using 60 T pulsed magnets. While the superconducting phase diagram (Tc, x) displays the classic dome-shaped structure, we find that the resistive upper critical field (Hc2) increases monotonically with decreasing fluorine concentration, with the largest Hc2 >= 75 T for x = 0.05. This is reminiscent of the composition dependence in high-Tc cuprates and might correlate with opening of a pseudo-gap in the underdoped region. Further, the temperature dependence of Hc2(T) for superconducting samples can be understood in terms of multi-band superconductivity. Rxy data for non-superconducting samples show non-linear field dependence, which is also consistent with a multi-carrier scenario.