1301.5257 (M. Abdel-Hafiez et al.)

Evidence for Line Nodes in the Superconducting Gap of
K_(1-x)Na_xFe_2As_2 (x = 0, 0.1) Single Crystals from Low-Temperature
Specific-Heat Measurements    [PDF]

M. Abdel-Hafiez, V. Grinenko, S. Aswartham, I. Morozov, M. Roslova, O. Vakaliuk, S. -L. Drechsler, S. Johnston, D. V. Efremov, J. van den Brink, H. Rosner, M. Kumar, C. Hess, S. Wurmehl, A. U. B. Wolter, B. Buechner, E. L. Green, J. Wosnitza, P. Vogt, A. Reifenberger, C. Enss, R. Klingeler

From the measurement and analysis of the specific heat of high-quality K_(1-x)Na_xFe_2As_2 single crystals we establish the presence of large T^2 contributions with coefficients alpha_sc ~ 30 mJ/mol K^3 at low-T for both x=0 and 0.1. This evidences line-nodes in the superconducting gap and suggests d-wave superconductivity on all Fermi-surface sheets with an average gap amplitude of Delta_0 in the range of 0.5 - 0.8 meV. The derived Delta_0 and observed T_c agree well with the values calculated within the Eliashberg-theory, adopting a spin-fluctuation mediated pairing in the intermediate coupling regime.

View original: http://arxiv.org/abs/1301.5257