Polarization Dependence of Optical Transitions in Graphene Nanoribbons
  The universality of $k$-dependent electron-photon and electron-phonon matrix elements is discussed for graphene nanoribbons and carbon nanotubes. An electron undergoes a change in wavevector in the direction of broken translational symmetry, depending on the light polarization direction. We suggest that this phenomenon originates from a microscopic feature of chirality. 
K. Sasaki and K. Kato and Y. Tokura and T. Sogawa and R. Saito
cond-mat.mes-hall cond-mat.mtrl-sci