Electron-phonon interaction and superconductivity in the borocarbide superconductor ScNi2B2C

Abstract

We have made an ab initio investigation of electron-phonon interaction and superconductivity in the borocarbide superconductor ScNi2B2C adopting the body-centred tetragonal LuNi2B2C-type of layered crystal structure. The calculated electronic structure and density of states suggest that the bonding is a combination of covalent, ionic and metallic in nature and that the Fermi level falls in one of the peaks in the electronic density of states. Our electron-phonon interaction calculations suggest that the mechanism for superconductivity is heavily governed by interactions of electrons with acoustic phonon modes and low-frequency optical phonon modes, which strongly modulate NiB4 tetrahedral bond angles. By integrating the Eliashberg spectral function, the value of average electronphonon coupling parameter is found to be 0.93 and the superconducting critical temperature is calculated to be 16.28 K, in excellent agreement with the experimentally reported value of 16.0 K.