Re-emergent direct-indirect band gap transitions in carbon nanotubes under shear strains

Abstract

Electronic structures of single-walled carbon nanotubes under varying shear strains are studied with the use of pseudopotential density functional method. We present a new scheme to induce shear strains in one-dimensional materials like nanotubes without introducing artificial edge atoms. It is found that the band gap of semiconducting zigzag nanotubes exhibits reemerging direct-indirect transitions as they are twisted. The breaking of the three-fold rotational symmetry and the electron-hole symmetry of corresponding graphitic band structures under shear is shown to be the origin of the behavior in the band gap. (C) 2008 Elsevier Ltd. All rights reserved.