Doping evolution of the absolute value of the London penetration depth and superfluid density in single crystals of Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$

Abstract

The zero temperature value of the in-plane London penetration depth, ${\lambda }_{ab}(0)$, has been measured in single crystals of Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ as a function of the Co concentration, $x$, across both the underdoped and overdoped superconducting regions of the phase diagram. For $x\gtrsim 0.047$, ${\lambda }_{ab}(0)$ has been found to have values between 120 $\pm$ 50~nm and 300 $\pm$ 50~nm. A pronounced increase in ${\lambda }_{ab}(0)$, to a value as high as 950 $\pm$ 50~nm, has been observed for $x\lesssim 0.047$, corresponding to the region of the phase diagram where the itinerant antiferromagnetic and superconducting phases coexist and compete. Direct determination of the doping-dependent ${\lambda }_{ab}(0)$ has allowed us to track the evolution of the temperature-dependent superfluid density, from which we infer the development of a pronounced superconducting gap anisotropy at the edges of the superconducting dome.

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• A Sharp Peak of the Zero-Temperature Penetration Depth at Optimal Composition in BaFe2(As1-xPx)2
• Local measurement of the superfluid density in the pnictide superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ across the superconducting dome
• Magnetic penetration depth in the presence of a spin-density wave in multiband superconductors at zero temperature
• Scaling of the physical properties in Ba(Fe,Ni)2As2 single crystals: Evidence for quantum fluctuations
• Comment on "Isoelectronic Ru substitution at Fe-site in Sm(Fe${}_{1-x}$Ru${}_x$)AsO${}_{0.85}$F${}_{0.15}$ compound and its effects on structural, superconducting and normal state properties" (arXiv:1004.1978)
• $a-b$ Plane Point Contact Spectroscopy measurements of optimally Cobalt doped Ba-122 iron-pnictide superconductors