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Quasiparticle heat transport in single-crystalline Ba(1-x)KxFe(2)As(2): Evidence for a k-dependent superconducting gap without nodes

TitleQuasiparticle heat transport in single-crystalline Ba(1-x)KxFe(2)As(2): Evidence for a k-dependent superconducting gap without nodes
Publication TypeJournal Article
Year of Publication2009
AuthorsLuo XG, Tanatar MA, Reid JP, Shakeripour H, Doiron-Leyraud N, Ni N, Bud'ko SL, Canfield PC, Luo HQ, Wang ZS, Wen HH, Prozorov R, Taillefer L
Journal TitlePhysical Review B
Volume80
Pages140503
Date Published10/01
ISBN Number1098-0121
Accession NumberISI:000271351500023
Keywordsba0.6k0.4fe2as2, d-wave superconductors, resolved photoemission-spectroscopy, state
Abstract

The thermal conductivity kappa of the iron-arsenide superconductor Ba1-xKxFe2As2 (T-c similar or equal to 30 K) was measured in single crystals at temperatures down to T not similar or equal to 50 mK (similar or equal to T-c/600) and in magnetic fields up to H = 15 T(similar or equal to H-c2/4). A negligible residual linear term in kappa/T as T -> 0 shows that there are no zero-energy quasiparticles in the superconducting state. This rules out the existence of line and in-plane point nodes in the superconducting gap, imposing strong constraints on the symmetry of the order parameter. It excludes d-wave symmetry, drawing a clear distinction between these superconductors and the high-T-c cuprates. However, the fact that a magnetic field much smaller than H-c2 can induce a residual linear term indicates that the gap must be very small on part of the Fermi surface, whether from strong anisotropy or band dependence, or both.
URL<Go to ISI>://000271351500023
DOI10.1103/Physrevb.80.140503