Effect of substitution on the superconducting phase of transition metal dichalcogenide Nb(Se $$_{x}$$ x S $$_{1-x}$$ 1 - x ) $$_{2}$$ 2 van der Waals layered structure

Abstract

Abstract By means of first-principles cluster expansion, anisotropic superconductivity in the transition metal dichalcogenide Nb(Se $$_{x}$$ x S $$_{1-x}$$ 1 - x ) $$_{2}$$ 2 forming a van der Waals (vdW) layered structure is observed theoretically. We show that the Nb(Se $$_{0.5}$$ 0.5 S $$_{0.5}$$ 0.5 ) $$_{2}$$ 2 vdW-layered structure exhibits minimum ground-state energy. The Pnnm structure is more thermodynamically stable when compared to the 2H–NbSe $$_{2}$$ 2 and 2H–NbS $$_{2}$$ 2 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(Se $$_{0.5}$$ 0.5 S $$_{0.5}$$ 0.5 ) $$_{2}$$ 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.