Gap generation in ABC-stacked multilayer graphene: screening vs band flattening

We calculate the dynamical polarization function and solve a self-consistent gap equation in the random phase approximation in undoped ABC-stacked n-layer graphene. We find that the gap is maximal in trilayer graphene and decreases monotonously for $n \ge 4$ because the effects of screening in the gap equation win over those connected with the flattening of electron bands as n increases.