Emergent superconductivity driven by Van Hove singularity in a Janus Mo2PS monolayer†

Abstract

Two-dimensional (2D) Janus structures with the breaking of out-of-plane mirror symmetry can induce many interesting physical phenomena, and have attracted widespread attention. Herein, we propose a Mo₂PS monolayer with mirror asymmetry, identified by first-principles structural search calculations, which demonstrates high thermodynamic and dynamic stability. Our findings reveal that Mo 4d-orbitals dominate the metallicity, significantly enhancing the density of states near the Fermi level due to Van Hove singularities (VHSs), leading to the existence of phonon-mediated superconductivity. Notably, tensile strain elevates the critical temperature (T_c) nearly tenfold, driven by strong coupling between softened acoustic modes of Mo vibrations and a new saddle point VHS at point X. These results highlight that the Janus Mo₂PS monolayer serves as a promising candidate for 2D straintronic applications with desirable physical properties.