Optical and magneto-optical far-infrared properties of bilayer graphene
  We analyze the spectroscopic features of bilayer graphene determined by the formation of pairs of low-energy and split bands in this material. We show that the inter-Landau-level absorption spectrum in bilayer graphene at high magnetic field is much denser in the far-infrared range than that in monolayer material, and that the polarization dependence of its lowest energy peak can be used to test the form of the bilayer ground state in the quantum Hall-effect regime. 
D.S.L. Abergel and Vladimir I. Fal'ko