Abstract
The temperature and magnetic field dependence of the in-plane thermal conductivity of the iron-arsenide superconductor was measured down to and up to as a function of Co concentration in the range . At , a negligible residual linear term in as at all shows that the superconducting gap has no nodes in the plane anywhere in the phase diagram. However, while the slow dependence of at in the underdoped regime is consistent with a superconducting gap that is large everywhere on the Fermi surface, the rapid increase in 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 -dependent amplitude.
- Received 7 July 2009
DOI:https://doi.org/10.1103/PhysRevLett.104.067002
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