Effect of substitution on the superconducting phase of transition metal dichalcogenide Nb(Se <inf>x</inf> S <inf>1</inf><inf>-</inf><inf>x</inf> ) <inf>2</inf> van der Waals layered structure

Abstract

By means of first-principles cluster expansion, anisotropic superconductivity in the transition metal dichalcogenide Nb(SexS1-x)2 forming a van der Waals (vdW) layered structure is observed theoretically. We show that the Nb(Se0.5S0.5)2 vdW-layered structure exhibits minimum ground-state energy. The Pnnm structure is more thermodynamically stable when compared to the 2H–NbSe2 and 2H–NbS2 structures. The characteristics of its phonon dispersions confirm its dynamical stability. According to electronic properties, i.e., electronic band structure, density of states, and Fermi surface indicate metallicity of Nb(Se0.5S0.5)2. The corresponding superconductivity is then investigated through the Eliashberg spectral function, which gives rise to a superconducting transition temperature of 14.5 K. This proposes a remarkable improvement of superconductivity in this transition metal dichalcogenide.