Nontrivial effect of out-of-plane acoustic phonon mode on limiting room temperature conductivity of ABA-stacked trilayer graphene

The ABA-stacked trilayer graphene (TLG) has a parabolic dispersion band spanning the Fermi level, apart from the linear dispersion band which is almost a duplicate of that in monolayer graphene (MLG). Such a band structure implies that the TLG is a metal and seemingly has a larger conductivity than MLG due to the additional contributions of the parabolic bands when the linear dispersion bands in TLG and MLG host the same number of carriers. However, our numerical calculations indicate that the conductivity of TLG is smaller than that in MLG roughly by 20% when a moderate carrier doping drives the Fermi energy away from the Dirac point by at least 50 meV. To explain such a disagreement between the band structure and the conductivity, we find that the out-of-plane atomic vibration, i.e., the so-called ZA phonon mode in the long-wavelength region, plays a critical role in limiting the conductivity of TLG due to the strong interband scattering. In contrast to MLG, such a ZA phonon mode is completely decoupled from the electron-phonon scattering due to the symmetry incompatibility.