High-temperature phonon-mediated superconductivity in monolayer Mg2B4C2.

A two-dimensional material – Mg₂B₄C₂, belonging to the family of the conventional superconductor MgB₂, is theoretically predicted to exhibit superconductivity with critical temperature T_c estimated in the 47–48 K range (predicted using the McMillian-Allen-Dynes formula) without any tuning of external parameters such as doping, strain, or substrate-induced effects. The origin of such a high intrinsic T_c is ascribed to the presence of strong electron-phonon coupling and large density of states at the Fermi level. This system is obtained after replacing the chemically active boron-boron surface layers in a MgB₂ slab by chemically inactive boron-carbon layers. Hence, the surfaces of this material are inert. Our calculations confirm the stability of 2D Mg₂B₄C₂. We also find that the key features of this material remain essentially unchanged when its thickness is increased by modestly increasing the number of inner MgB₂ layers. [ABSTRACT FROM AUTHOR]