Prediction of superconductivity at 70 K in a pristine monolayer of LiBC

Search of high-temperature superconductors has gained huge impetus since the discovery of superconductivity in bulk $\mathrm{Mg}{\mathrm{B}}_{2}$. These efforts led to the synthesis of high-${T}_{C}$ materials in the megabar pressure region. However, the ultimate goal of a room-conditions superconductor is still elusive. Toward this, a class of two-dimensional (2D) superconductors is emerging as a fertile field of research. In this paper, by solving fully anisotropic Migdal-Eliashberg equations, we show that a pristine monolayer (ML) of LiBC will be a Bardeen-Cooper-Schrieffer-type superconductor with a record-breaking ${T}_{C}$ of 70 K among pure 2D superconductors. The critical temperature could be further increased by hydrogenation of the ML. Analysis of the electronic properties indicates the partial change of B-C covalent bonding from $s{p}^{2}$ to $s{p}^{3}$ type on bulk-to-ML transformation. This paper presents a proposal to metalize the LiBC system, which was long been predicted to show superconductivity in its bulk form with 50% Li site vacancies. This system might be useful for the design and development of high-${T}_{C}$ 2D superconductors that could be applied in devices like quantum interferometers, superconducting qubits, or superconducting transistors.