Optical properties of nanographite ribbons

The optical properties of nanographite ribbons are studied within the gradient approximation. The spectral function exhibits rich peak structures due to the divergencies in its density of states. Whether there are prominent peak structures is mainly determined by the geometric structure. the edge structure and the width. The spectral function also depends on the chemical potential and the temperature (except in the case of narrow armchair ribbons). Important differences between zigzag ribbons and armchair ribbons include the validity of the DeltaJ = 0 selection rule, the frequency range of the absorption peaks, the very special absorption peak at gamma (0) or 2(gamma0), and the temperature dependence.