Superconducting properties in doped 2M-WS2 from first principles

Abstract

A new member of the transition metal dichalcogenide (TMD) family, 2M-WS₂, has been recently discovered and shown to display superconductivity with a critical temperature (T_c) of 8.8 K, the highest T_c among superconducting TMDs at ambient pressure. Using first-principles calculations combined with the Migdal-Eliashberg formalism, we explore how the superconducting properties of 2M-WS₂ can be enhanced through doping. Mo, Nb, and Ta are used as dopants at the W sites, while Se is used at the S sites. We demonstrate that the monotonous decrease in the T_c observed experimentally for Mo and Se doping is due to the decrease in density of states at the Fermi level and the electron–phonon coupling of the low-energy phonons. In addition, we find that a noticeable increase in the electron–phonon coupling could be achieved when doping with Nb and Ta, leading to an enhancement of the T_c of up to 50% compared to the undoped compound.