Unconventional Superconductivity in Electron-Doped Layered Li0.48(THF)yHfNCl

Abstract

We report magnetic susceptibility measurements on a layered superconductor Li0.48(THF)0.3HfNCl having Tc∼26 K. The present study revealed that (a) the Fermi level density of states is small, N*(EF)∼0.25 states/(eV spin f .u.), (b) mass enhancement is negligible, γ̃∼1, (c) electron-phonon coupling is weak, λep≪1, (d) exchange enhancement is negligible, 1/(1+F0a)∼1, and (e) electronic density parameter is large, rs2D∼10.3 (i.e., low-carrier density). It is difficult to explain the origin of the high Tc in terms of the conventional phonon (BCS) mechanism of superconductivity