Theoretical prediction of superconductivity in monolayer CoO2

Abstract

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 highest-temperature 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.