Doping evolution of the absolute value of the London penetration depth and superfluid density in single crystals of Ba(Fe1-xCox)2As2

• Published in: Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2010-08, Vol.82 (5)
• Main Authors: Gordon, R. T., Kim, H., Salovich, N., Giannetta, R. W., Fernandes, R. M., Kogan, V. G., Prozorov, T., Bud’ko, S. L., Tanatar, M. A., Prozorov, R., Canfield, P. C.
• Format: Article
• Language: English
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; energy storage (including batteries and capacitors); phonons; spin dynamics; superconductivity, defects; thermal conductivity
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.82.054507

The zero-temperature value of the in-plane London penetration depth, λab (0) , has been measured in single crystals of Ba(Fe1-x Cox)₂ As₂ as a function of the Co concentration, x , across both the underdoped and overdoped superconducting regions of the phase diagram. For x ≳ 0.047 , λab (0) has been found to have values between 120 ± 50 and 300 ± 50 nm . A pronounced increase in λab (0) , to a value as high as 950 ± 50 nm , has been observed for x ≲ 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 λab (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.