Optical properties of nanographite ribbons

The optical properties of nanographite ribbons are studied within the gradi ent approximation. The spectral function exhibits rich peak structures due to the divergencies in its density of states. Whether there are prominent p eak structures is mainly determined by the geometric structure. the edge st ructure and the width. The spectral function also depends on the chemical p otential and the temperature (except in the case of narrow armchair ribbons ). Important differences between zigzag ribbons and armchair ribbons includ e 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(gamma 0), and the temperature dependence.