Specific heat measurement of the layered nitride superconductor LixZrNCl -: art. no. 217002

Specific heat has been investigated in a layered nitride superconductor, Li0.12ZrNCl, with T-c=12.7 K. The obtained data have shown a marked dichotomy: The specific heat jump at T-c (Delta C/gamma T-n(c)=1.8) and the superconducting gap ratio (2 Delta/k(B)T(c)=4.6-5.2) have indicated an intermediate to a strong coupling of electrons, while the upper limit of the electron-phonon coupling constant lambda has directly been estimated to be 0.22, which belongs to a weak coupling regime. Furthermore, the rapid increase of gamma as a function of magnetic field suggests that the present material has an anisotropic s wave gap.