Magneto-Optical Absorption in Graphene Superlattices: Dirac Point Effects

We investigate the effects of Dirac points on the magneto-optical absorption of graphene superlattices (SLs) in a weak perpendicular magnetic field. It is shown that the absorption spectrum exhibits a resonant peak structure whose characteristics depend on the properties and number of these points. For SLs with only one Dirac point, the spectrum consists of resonant peaks satisfying the same selection rule as that for monolayer graphene, except for one of these peaks. For SLs with extra Dirac points, the resonant peaks arise from transition between singlet subbands or between doublet subbands and satisfy a circular polarization and peak intensity dependent selection rule.