Campus Units
Physics and Astronomy, Ames Laboratory
Document Type
Article
Publication Version
Published Version
Publication Date
8-1-2010
Journal or Book Title
Physical Review B
Volume
82
Issue
6
First Page
064501
DOI
10.1103/PhysRevB.82.064501
Abstract
The thermal conductivity κ of the iron-arsenide superconductor Ba(Fe1−xCox)2As2 was measured down to 50 mK for a heat current parallel (κc) and perpendicular (κa) to the tetragonal c axis for seven Co concentrations from underdoped to overdoped regions of the phase diagram (0.038≤x≤0.127). A residual linear term κc0/T is observed in the T→0 limit when the current is along the c axis, revealing the presence of nodes in the gap. Because the nodes appear as x moves away from the concentration of maximal Tc, they must be accidental, not imposed by symmetry, and are therefore compatible with an s± state, for example. The fact that the in-plane residual linear term κa0/T is negligible at all x implies that the nodes are located in regions of the Fermi surface that contribute strongly to c-axis conduction and very little to in-plane conduction. Application of a moderate magnetic field (e.g., Hc2/4) excites quasiparticles that conduct heat along the a axis just as well as the nodal quasiparticles conduct along the c axis. This shows that the gap must be very small (but nonzero) in regions of the Fermi surface which contribute significantly to in-plane conduction. These findings can be understood in terms of a strong k dependence of the gap Δ(k) which produces nodes on a Fermi-surface sheet with pronounced c-axis dispersion and deep minima on the remaining, quasi-two-dimensional sheets.
Copyright Owner
American Physical Society
Copyright Date
2010
Language
en
File Format
application/pdf
Recommended Citation
Reid, J.-Ph.; Tanatar, Makariy A.; Luo, X. G.; Shakeripour, H.; Doiron-Leyraud, N.; Ni, Ni; Bud’ko, Sergey L.; Canfield, Paul C.; Prozorov, Ruslan; and Taillefer, Louis, "Nodes in the gap structure of the iron arsenide superconductor Ba(Fe(1-x)Cox)(2)As-2 from c-axis heat transport measurements" (2010). Physics and Astronomy Publications. 692.
https://lib.dr.iastate.edu/physastro_pubs/692
Comments
This article is published as Reid, J-Ph, M. A. Tanatar, X. G. Luo, H. Shakeripour, N. Doiron-Leyraud, Ni Ni, S. L. Bud’ko, P. C. Canfield, R. Prozorov, and Louis Taillefer. "Nodes in the gap structure of the iron arsenide superconductor Ba (Fe 1− x Co x) 2 As 2 from c-axis heat transport measurements." Physical Review B 82, no. 6 (2010): 064501. DOI: 10.1103/PhysRevB.82.064501. Posted with permission.