The thermal conductivity of borocarbide superconductor LuNi_2B_2C was measured down to 70 mK (T_c/200) in a magnetic field perpendicular to the heat current from H = 0 to above H_c2 = 7 T. As soon as vortices enter the sample, the conduction at T -> 0 grows rapidly, showing unambiguously that delocalized quasiparticles are present at the lowest energies. The field dependence is very similar to that of UPt_3, a heavy-fermion superconductor with a line of nodes in the gap, and very different from the exponential dependence characteristic of s-wave superconductors. This is strong evidence for a highly anisotropic gap function in LuNi_2B_2C, possibly with nodes.
@article{arxiv.cond-mat/0108409,
title = {Highly Anisotropic Gap Function in Borocarbide Superconductor LuNi_2B_2C},
author = {Etienne Boaknin and R. W. Hill and Cyril Proust and C. Lupien and Louis Taillefer and P. C. Canfield},
journal= {arXiv preprint arXiv:cond-mat/0108409},
year = {2009}
}
Comments
5 pages, 3 figures, Revised version, as appears in Phys. Rev. Lett