First Principles Predictions of Superconductivity in Doped Stanene

Stanene, composed of tin atoms arranged in a single layer, is the tin analogue of graphene and past studies predicted it to be a topological insulator. An energy band gap (of $\sim 0.1$~eV) was obtained in previous calculations for the buckled honeycomb structure of stanene and, thus, phonon-mediated superconductivity in this material is ruled out. In this work we investigated, from first principles calculations within density functional theory (DFT), the possibility of producing phonon-mediated superconductivity in stanene by doping the material. It was found that doping with calcium (lithium) leads to superconductivity, albeit, with a very low superconducting transition temperature $T_c$ of $\sim 0.7$~K ($\sim 1.3$~K), even lower than the value ($3.7$~K) for bulk $\beta$-Tin.