Electron-phonon interaction and superconductivity in SnAs with the sodium chloride crystal structure

The ground state and electronic properties of the recently discovered superconducting SnAs in the sodium chloride crystal structure have been examined using density functional theory within the generalized gradient approximation. The results indicate that the density of states at the Fermi level is primarily derived from As p states, which strongly hybridize with Sn p states. The phonon dispersion curves and the phonon density of states are calculated using the Density Functional Perturbation Theory. By integrating the Eliashberg spectral function, the average electron-phonon coupling parameter is found to be λ=0.64. Using this value the superconducting critical temperature Tc is estimated to be 3.24 K, which is in good accordance with its experimental value of 3.58 K. The agreement between our results and the experimentally derived results for λ and Tc supports the concept of single valence state for Sn in the three-dimensional NaCl structure by Wang et al. [Chem. Mater. 26 (2014) 7209] [10].