Prediction of anisotropic single-gap superconductivity in the tetragonal MoS2 monolayer

Using first-principles calculations, we investigate a tetragonal δ phase of monolayer MoS 2 as an intrinsic two-dimensional superconducting candidate and assess its structural stability through formation-energy, elastic-constant, and phonon calculations. By solving the fully anisotropic Migdal-Eliashberg equations, we predict a single anisotropic superconducting gap and a superconducting transition temperature of 8.4 K. The superconductivity is driven by strong electron-phonon coupling (λ = 1.66), which mainly originates from low-energy phonons. In particular, Mo-dominated acoustic modes and low-frequency optical modes associated with S vibrations provide the dominant contributions to the total electron-phonon coupling. The phonon dispersion shows an overlap between the lowest optical branch and the highest acoustic branch near the M point, accompanied by pronounced phonon softening, while Mo-d orbitals dominate the electronic states near the Fermi level with van Hove features around the Γ and X points. These results indicate that the predicted tetragonal MoS 2 is a structurally stable two-dimensional superconductor, which could provide a valuable platform for further exploration of 2D superconductivity in transition metal dichalcogenides.