Local measurement of the superfluid density in the pnictide superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ across the superconducting dome

Abstract

We measure the penetration depth ${\lambda }_{ab}(T)$ in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ using local techniques that do not average over the sample. The superfluid density ${\rho }_s(T)\equiv 1/{\lambda }_{ab}(T{)}^2$ has three main features. First, ${\rho }_s(T=0)$ falls sharply on the underdoped side of the dome. Second, ${\lambda }_{ab}(T)$ is flat at low $T$ at optimal doping, indicating fully gapped superconductivity, but varies more strongly in underdoped and overdoped samples, consistent with either a power law or a small second gap. Third, ${\rho }_s(T)$ varies steeply near $T_c$ for optimal and underdoping. These observations are consistent with an interplay between magnetic and superconducting phases.

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Cited by in corpus (2)

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