Theoretical investigation of superconductivity in ternary silicide NaAlSi with layered diamond-like structure

Abstract

We have investigated the electronic structure, phonon modes and electron–phonon coupling to understand superconductivity in the ternary silicide NaAlSi with a layered diamond-like structure. Our electronic results, using the density functional theory within a generalized gradient approximation, indicate that the density of states at the Fermi level is mainly governed by Si p states. The largest contributions to the electron–phonon coupling parameter involve Si-related vibrations both in the x–y plane as well as along the z-axis in the x–z plane. Our results indicate that this material is an s-p electron superconductor with a medium level electron–phonon coupling parameter of 0.68. Using the Allen–Dynes modification of the McMillan formula we obtain the superconducting critical temperature of 6.98 K, in excellent agreement with experimentally determined value of 7 K.