Electron-phonon superconductivity in non-centrosymmetric LaNiC2: first principles calculations

Abstract

We report first principles calculations of the electronic structure and electron-phonon coupling in the non-centrosymmetric superconductor LaNiC2. These show that the material is a conventional electron-phonon superconductor with intermediate coupling. There are large contributions to the coupling by two low frequency C non-bond-stretching modes, one of which has strong Kohn anomalies. Since LaNiC2 lacks inversion symmetry, the pairing is of dominant $s$-wave type with some mixture of $p$-wave character. This will give exponential decay in the specific heat and can at the same time break time-reversal symmetry.