title: Doping dependence of heat transport in the iron-arsenide superconductor Ba(Fe(1-x)Co(x))2As2: from isotropic to a strongly k-dependent gap structure.
abstract: The temperature and magnetic field dependence of the in-plane thermal conductivity kappa of the iron-arsenide superconductor Ba(Fe(1-x)Co(x))2As2 was measured down to T approximately 50 mK and up to H = 15 T as a function of Co concentration x in the range 0.048 < or = x < or = 0.114. At H = 0, a negligible residual linear term in kappa/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 kappa(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 kappa(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.
authors.affiliation: Ames Laboratory, Ames, Iowa 50011, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Tanatar
authors.forename: J-Ph
authors.initials: JP
authors.lastname: Reid
authors.forename: H
authors.initials: H
authors.lastname: Shakeripour
authors.forename: X G
authors.initials: XG
authors.lastname: Luo
authors.forename: N
authors.initials: N
authors.lastname: Doiron-Leyraud
authors.forename: N
authors.initials: N
authors.lastname: Ni
authors.forename: S L
authors.initials: SL
authors.lastname: Bud'ko
authors.forename: P C
authors.initials: PC
authors.lastname: Canfield
authors.forename: R
authors.initials: R
authors.lastname: Prozorov
authors.forename: Louis
authors.initials: L
authors.lastname: Taillefer