Doping dependence of heat transport in the iron-arsenide superconductor Ba(Fe1-xCox)2As2: from isotropic to a strongly κ-dependent gap structure --- Physical Review Letters 104,067002 (2010) / arXiv:0907.1276v2
Doping dependence of heat transport in the iron-arsenide superconductor Ba(Fe1-xCox)2As2: from isotropic to a strongly κ-dependent gap structure
M. A. Tanatar1, J.-Ph. Reid2, H. Shakeripour2, X. G. Luo2, N. Doiron-Leyraud2, N. Ni1,3 , S. L. Bud’ko1,3, P. C. Canfield 1,3, R. Prozorov1,3, and Louis Taillefer1,4,*
1.Ames Laboratory, Ames, Iowa 50011, USA
2.Departement de physique & RQMP, Universite de Sherbrooke, Sherbrooke, Canada
3.Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
4.Canadian Institute for Advanced Research, Toronto, Ontario, Canada
The temperature and magnetic field dependence of the in-plane thermal conductivity of the iron- arsenide superconductor Ba (Fe1-xCox)2As2 was measured down to about T= 50 mK and up to H=15 T as a function of Co concentration x in the range 0.048 < = x < = 0.114. At H=0, a negligible residual linear term in in κ/T as T → 0 at all x shows that the superconducting gap has no nodes in the ab plane anywhere in the phase diagram. However, while the slow H dependence of κ(H) at T → 0 in the underdoped regime is consistent with a superconducting gap that is large everywhere on the Fermi surface, the rapid increase in κ(H) observed in the overdoped regime shows that the gap acquires a deep minimum somewhere on the Fermi surface. Outside the antiferromagnetic-orthorhombic phase, the superconducting gap structure has a strongly k-dependent amplitude.