Theoretical prediction of superconductivity in monolayer CoO₂

Motivated by the synthesis of the layered structure CoO₂via Li atom deintercalation from Li_xCoO₂, herein, we investigated the electronic structure, lattice dynamics, electron-phonon interaction, and superconductivity of monolayer CoO₂ using first-principles calculations. This 2D material was predicted to have a ferromagnetic ground state with a metallic band structure and the total magnetization of 0.83μ_B. Remarkably, the non-spin polarized calculations show that the monolayer CoO₂ possesses phonon-mediated superconductivity at 25-28 K owing to its intermediate to strong electron-phonon coupling (EPC). The rather strong EPC in this compound is mainly driven by the acoustic phonons, making this compound one of the highesterature superconductors among the existing 2D materials. Moreover, the CoO₂ sheets could be synthesized via exfoliation from bulk CoO₂ owing to the relatively small interlayer binding energy while maintaining its stability under normal experimental conditions. Compared to its bulk and bilayer counterparts, monolayer CoO₂ was found to have highest EPC.