Strong-coupling superconductivity with Tc above 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 BeC2 is metallic, thus, the possible phonon-mediated superconductivity is explored based on the Eliashberg equation. The calculated electron-phonon coupling (EPC) constant lambda is up to 4.07, and the corresponding superconducting critical temperature (T-c) is 72.1 K, approaching the liquid nitrogen temperature. The reason for the high T-c is the strong EPC. And it is proved to be an anisotropic single-gap superconductor by analyzing the superconducting gap Delta(k) of BeC2. The electronic susceptibility calculation shows strong nesting effect in BeC2. Since rare 2D superconductors show such a strong EPC constant lambda which originates from the coupling between electrons in C-p(z) orbital and in-plane vibrations of Be and C atoms, the predicted BeC2 provides a new platform for investigating strong EPC 2D superconductor.