Theoretical limits of electron and hole doping in single-layer graphene from DFT calculations

Density functional theory calculations suggest a pronounced hole-electron doping asymmetry in single-layer graphene. It turns out that a single graphene sheet can sustain doping levels of up to 0.1 holes or up to a remarkably large 1.9 electrons per atom while maintaining dynamical (phonon) stability. Estimates of the superconducting critical temperature in the electron-doped regime based on McMillan's formula reveal two local maxima in the function of the doping level, which correlate with the local maxima of the electron-phonon coupling constant.