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 λ 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 Δ_k of BeC₂. The electronic susceptibility calculation shows strong nesting effect in BeC₂. Since rare 2D superconductors show such a strong EPC constant λ 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. [ABSTRACT FROM AUTHOR]