Prediction of charge density wave, superconductivity and topology properties in two-dimensional Janus 2H/1T-W X H ( X = S, Se)

The multiple properties in two-dimensional (2D) materials have attracted widespread attention. Utilizing first -principles calculations, we theoretically predict four 2D transition metal Janus sulfide hydrides, named 2H/1T-W X H ( X = S, Se). The 2H-WSH and 2H - WSeH demonstrate superconductivity with critical temperatures ( T c ) of 13.4 K and 11.4 K, respectively. Whereas 1T-WSH and 1T-WSeH display charge density wave (CDW) properties arising from electron -phonon coupling (EPC). It is noteworthy that the CDW can be suppressed through biaxial compressive strain, leading to the emergence of superconductivity with T c of 12.2 K and 11.9 K for 1T-WSH (-2 %) and 1T-WSeH (-4 %), respectively. The superconductivity of the above materials originates from the coupling between W -3 d electrons and the lowfrequency vibrations of W. Interestingly, the 2H - WSeH and 1T-WSeH (-4 %) display nontrivial topological properties, as evidenced by topological invariant Z 2 and the presence of edge states. Our research not only provides theoretical guidance for further exploring 2D Janus materials, but also provides ideas for the competition of multiple orders in 2D materials.