High-temperature superconductivity in a two-dimensional electride

Electrides constitute a unique class of materials that can be developed as conventional superconductors with diverse dimensional superconductivity. However, the transition temperatures $({T}_{c})$ of electride superconductors are generally low and promoting their ${T}_{c}$ usually requires extremely high external pressures that are formidable for practical applications. Here, based on the first-principles calculations, we proposed that the recently reported electride, ${\mathrm{Be}}_{2}\mathrm{N}$, can exhibit a two-dimensional (2D) superconductivity, which has a ${T}_{c}$ of 10.3 K that is the highest ${T}_{c}$ ever found for bulk electride superconductors at ambient pressure. More interestingly, we found that the high ${T}_{c}$ of ${\mathrm{Be}}_{2}\mathrm{N}$ is mainly attributed to the large average phonon frequency, rather than the strong electron-phonon coupling, which can be further understood by the small atomic weight of Be atoms and the strong Be-N bonds. Moreover, compared to most conventional superconductors, we identified an unusual dependence of the superconductivity of ${\mathrm{Be}}_{2}\mathrm{N}$ on external pressures, originating from a unique charge transfer from its cationic framework to its anionic electron cloud. Our studies provide a deeper understanding of the superconductivity of 2D electrides and suggest a feasible way for the development of high-temperature electride superconductors at ambient pressure.