σ Bands Driven High-Temperature Superconductivity in Hydrogenated Hexagonal BC 3 Monolayer

Abstract Material with metallic σ-bonding bands is expected to be a high-temperature superconductor, due to the sensitivity of σ electrons to lattice vibration. Based on the first-principles calculations, electronic structures of hydrogenated BC 3 monolayers (H n -B 2 C 6 with n = 1–8) are systematically investigated. At high coverage of hydrogen, the monolayer stabilizes in chair-like sp 3 -hybridized configurations, leading to the metallization of σ bands, especially in H 7 -B 2 C 6 and H 8 -B 2 C 6 . This metallicity originates from the electron deficiency of boron, compared with insulating graphane. Utilizing Wannier interpolation, the electron-phonon coupling strengths for metallic phases of H n -B 2 C 6 are determined. As expected, strong couplings are identified between the conducting σ electrons and low-frequency phonon modes. By solving the anisotropic Eliashberg equations, we confirm that H 7 -B 2 C 6 and H 8 -B 2 C 6 are single-gap superconductors with critical temperature being 91 K and 87 K, respectively, exceeding the boiling point of liquid nitrogen. Considering that monolayer BC 3 has been synthesized in experiment, our results demonstrate that hydrogenation of two-dimensional BC 3 provides a viable pathway to achieve high-temperature superconductivity at ambient pressure.