Weak electron-phonon coupling in layered electrides

In layered electrides, the conducting electrons fill the two-dimensional interstitial voids between the atomic planes, which is expected to result in weakened electron-phonon coupling and give rise to high mobility and conductivity. In this paper, using density functional theory, we explore the room-temperature electron-phonon scattering and transport properties of seven layered electrides belonging to the alkaline earth subpnictogenide family (Ca2N, Sr2N, Sr2P, Ba2N, Ba2P, Ba2As, and Ba2Sb) and compare them to three traditional highconductivity metals (Cu, Au, and Al). Several electrides are found to have low scattering rates compared with the metals, resulting from weak electron-phonon interaction, between 3 and 13x lower than the metals, which is shown to originate from the spatial separation of the conducting electrons from the lattice. Sr2N and Ca2N are predicted to be the best conductors among the electrides, with high anisotropy, due to reduced scattering leading to long average mean-free paths for backscattering reaching 48 nm. However, the metals display the highest conductivities owing to their larger distribution of modes, originating from higher electronic velocities. These findings may help guide the discovery of electrides with exceptionally weak electron-phonon coupling and record high conductivity.