Phonon anomaly and anisotropic superconducting gap in non-centrosymmetric Li2(Pd1-xPtx)3B

Abstract

We report the systematic investigation of the specific heat of the noncentrosymmetric superconductor Li2(Pd1−xPtx)3B as a function of x. There is a large deviation of the phononic specific heat from the conventional Debye specific heat for Pt-rich samples. In contrast with the fully-gapped conventional behavior for small x, a power-law temperature dependence of the electronic specific heat is observed even at x = 0.5. This results manifest a strongly-anisotropic or nodal superconducting gap even at x = 0.5 and a nodal superconducting gap for x 0.9.