Superconductivity and strain-enhanced phase stability of Janus tungsten chalcogenide hydride monolayers

Janus transition metal-dichalcogenide (JTMD) materials have attracted a great deal of attention due to their remarkable physical properties arising from the two-dimensional geometry and the breakdown of the out-of-plane symmetry. Using first-principles density functional theory, we investigated the phase stability, strain-enhanced phase stability, and superconductivity of Janus WSeH and WSH. In addition, we investigated the contribution of the phonon linewidths from the phonon energy spectrum responsible for the superconductivity, and the electron-phonon coupling as a function of phonon wave vectors and modes. Previous work has examined hexagonal 2H and tetragonal 1T structures, but we found that neither is a ground state structure. The metastable 2H phase of WSeH is dynamically stable with Tc around 11.60K, similar to WSH. Compressive biaxial strain - the 2D equivalent of pressure - can stabilize the 1T structures of WSeH and WSH with Tc around 9.23K and 10.52K, respectively.