Electron-phonon interaction in a Ca2N monolayer: Intrinsic mobility of electrene

The electron-phonon (e-ph) interaction in ${\mathrm{Ca}}_{2}\mathrm{N}$ monolayer, the first electrene material with two-dimensional (2D) electron gas floating in free space, is expected to be very weak, which can be used to design weak-scattering transport channels. Therefore, it is highly desirable to quantitatively evaluate the carrier mobility of this electrene material. In this study, the e-ph interaction in ${\mathrm{Ca}}_{2}\mathrm{N}$ monolayer is investigated by using a precise Wannier interpolation-based first-principles technique. The calculated e-ph coupling matrix elements of ${\mathrm{Ca}}_{2}\mathrm{N}$ monolayer are indeed small compared with other 2D materials such as graphene, which leads to an intrinsic mobility of $189\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$, which is much higher than those of conventional metals. Other factors affecting mobility are discussed in a comparison with graphene. It is predicted that, based on a momentum mismatch mechanism, mobility of the ${\mathrm{Ca}}_{2}\mathrm{N}$ monolayer can be increased further to above $3000\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ via hole doping. Our results confirm that ${\mathrm{Ca}}_{2}\mathrm{N}$ electrene is a promising electronic material.