Polarization-sensitive absorption of THz radiation by interacting   electrons in chirally stacked multilayer graphene
  We show that opacity of a clean multilayer graphene flake depends on the helicity of the circular polarized electromagnetic radiation. The effect can be understood in terms of the pseudospin selection rules for the interband optical transitions in the presence of exchange electron-electron interactions which alter the pseudospin texture in momentum space. The interactions described within a semi-analytical Hartree--Fock approach lead to the formation of the topologically different broken--symmetry states characterized by Chern numbers and zero-field anomalous Hall conductivities. 
Maxim Trushin and John Schliemann
cond-mat.mes-hall cond-mat.str-el