MSene: A new large family of two-dimensional transition metal sulfide with MXene structure

Nowadays, discovering new two-dimensional (2D) materials with unique properties and potential applications remains a focus in condensed matter physics. Here, based on first-principles calculations, we report a new large family of transition metal sulfides M2S with MXene structure in 2H and 1T phases, which we name as MSene. Twenty-four out of fifty-eight MSenes are proved to be stable. Notably, this family includes twelve superconducting (SC) materials, seven SC topological metals (SCTMs), four charge density wave (CDW) materials, and five magnetic materials including one ferromagnetic (FM) and four antiferromagnetic (AFM) materials. For example, 2H-W2S is a SCTM which exhibits SC transition temperature (Tc) of 12.4 K and nontrivial topological properties as evidenced by topological invariant Z2=1 and the presence of edge states; 1T-Hf2S is a CDW material with the CDW originating from electron-phonon coupling. The CDW can be suppressed by compressive strain, leading to the emergence of superconductivity; 2H-Cr2S and 1T-Mn2S show FM and AFM properties, respectively. Thus, the new large family we predicted shows rich physical properties and significantly expands the repertoire of 2D materials. It serves as a novel platform for investigating the competition or coexistence of multiple orders such as SC, CDW, FM, AFM and topological orders in 2D materials.