Stability and superconductivity of freestanding two-dimensional transition metal boridene: MB.

The small atomic mass of boron indicates strong electron-phonon coupling (EPC), so it may have a brilliant performance in superconductivity. Recently, a new 2D boride sheet with ordered metal vacancies and surface terminals (MoB) was realized in experiments (Zhou2021801). Here, the 2D monolayer freestanding MoBis evidenced to be thermodynamically stable. Through electronic structure, phonon spectrum and EPC, monolayer MoBis found to be an intrinsic phonon-mediated superconductor. The superconducting transition temperature () is determined to be 4.06 K by the McMillian-Allen-Dynes formula. Remarkably, theof monolayer MoBcan be increased to 6.78 K with an appropriate biaxial tensile strain (+5%). Moreover, we predict that other transition metal replacing Mo atoms is also stable and retaining the superconductivity. Such as monolayer WBis also a superconductor with theof 2.37 K. Our research results enrich the database of 2D monolayer superconductors and boron-related formed materials science.