Electronic properties and optical spectra of Mo S2 and W S2 nanotubes

Abstract

Symmetry based calculations of the polarized optical absorption in single-wall Mo S2 and W S2 nanotubes are presented. Optical conductivity tensor for the individual tubes, using line group symmetry and density-functional tight binding implemented in POLSYM code, is numerically evaluated and its dependence on the diameter and chiral angle of the nanotubes is investigated. This minimal, full symmetry implementing algorithm enabled calculations of the optical response functions very efficiently and addressed the large diameter tubes and highly chiral tubes as well. It is predicted that, due to the symmetry transformation properties of the relevant electronic states, fluorescence is not expected in the metal dichalcogenide tubes. In accordance with the measurements, the calculations show redshift of the absorption peaks as the tube diameter increases. Also, it is found that curvature strain induces strong chiral angle dependence of the absorption spectra. © 2007 The American Physical Society.