Quantum interference induced by nonmagnetic impurities in a single-walled carbon nanotube

The scanning tunnelling spectroscopy of a doped single-walled armchair carbon nanotube has been investigated by using the $\pi$-electron tight-binding model. The spatial oscillations arising from quantum interference between the forward and backward electron waves are found in the local density of states. These oscillations are strongly dependent on the geometric arrangement of the relationship between the doped nonmagnetic impurities. Three typical oscillations are predicted and their characteristic features have been studied in detail. It is found that the symmetry and parity of the quasibound states induced by impurities are important to distinguish the oscillation types.