Strong-coupling superconductivity with Tcabove 70 K in Be-decorated monolayer T-graphene

Using first-principles calculations, we predict a new type of two-dimensional (2D) beryllium(Be)-decorated T-graphene named BeC2, where Be atoms are inserted into C–C bonds linking the carbon tetrarings of T-graphene. The band structure shows that BeC2is metallic, thus, the possible phonon-mediated superconductivity is explored based on the Eliashberg equation. The calculated electron-phonon coupling (EPC) constant λis up to 4.07, and the corresponding superconducting critical temperature (Tc) is 72.1 K, approaching the liquid nitrogen temperature. The reason for the high Tcis the strong EPC. And it is proved to be an anisotropic single-gap superconductor by analyzing the superconducting gap Δkof BeC2. The electronic susceptibility calculation shows strong nesting effect in BeC2. Since rare 2D superconductors show such a strong EPC constant λwhich originates from the coupling between electrons in C–pzorbital and in-plane vibrations of Be and C atoms, the predicted BeC2provides a new platform for investigating strong EPC 2D superconductor.