7 research outputs found
Evidence of d-wave Superconductivity in K_(1-x)Na_xFe_2As_2 (x = 0, 0.1) Single Crystals from Low-Temperature Specific Heat Measurements
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. Together with the observed square root field behavior of the specific
heat in the superconducting state both findings evidence d-wave
superconductivity on almost all Fermi surface sheets with an average gap
amplitude of Delta_0 in the range of 0.4 - 0.8 meV. The derived Delta_0 and the
observed T_c agree well with the values calculated within the Eliashberg
theory, adopting a spin-fluctuation mediated pairing in the intermediate
coupling regime.Comment: 8 pages, 5 figures, field dependence of the specific heat added,
slightly changed title, changed sequence of authors, one author added,
accepted by Phys. Rev. B Rapid Communication
Investigation of LiFeAs by means of "Break-junction" Technique
In our tunneling investigation using Andreev superconductor - normal metal -
superconductor contacts on LiFeAs single crystals we observed two reproducible
independent subharmonic gap structures at dynamic conductance characteristics.
From these results, we can derive the energy of the large superconducting gap
meV and the small gap meV at
K for the K (the contact area
critical temperature which deviation causes the variation of ). The
BCS-ratio is found to be , whereas
results from induced superconductivity in the bands
with the small gap.Comment: 7 pages, 5 figures. Published in Pis'ma v ZhETF 95, 604-610 (2012