Optical Absorption in Collapsed Carbon Nanotubes

Abstract

The optical absorption spectra are calculated in collapsed carbon nanotubes, described by dynamical conductivity σyy(ω) for the polarization of electric field parallel to the axis, and \(\tilde{\sigma }_{xx}^{\| }(\omega )\) and \(\tilde{\sigma }_{xx}^{ \bot }(\omega )\) perpendicular to the axis and parallel and perpendicular, respectively, to the flattened region. For σyy(ω), clear interband peaks appear corresponding to band gaps between allowed bands. Inter-wall interaction due to collapsing causes splitting and shift of the peaks from uncollapsed tubes. Such effects are largest in nonchiral zigzag and armchair tubes, for which the spectra depends on the relative displacement in the flattened region, and rapidly decrease for tubes with chiral structure. Depolarization effect suppresses interband absorption in \(\tilde{\sigma }_{xx}^{\| }(\omega )\) and \(\tilde{\sigma }_{xx}^{ \bot }(\omega )\). For \(\tilde{\sigma }_{xx}^{ \bot }(\omega )\), the rapid spatial variation of the effective electric field...