Anharmonic helical oscillator in single-walled carbon nanotubes

Abstract

The dynamic behaviour of a particle, as simple as a helium atom, traveling in a single-walled carbon nanotube is investigated. Applying an anisotropic Yukawa-6 potential to the He-C pair interaction and using the symmetry of the tube, we calculate the potential profiles in nanotubes. It was found that each of the three types of nanotubes is endowed with a separate potential profile structure that distinctly reflects its chirality feature. With appropriate initial conditions, the He atom is shown to travel helically along the axis of a nanotube and to longitudinally undergo anharmonic oscillation between its two ends a behaviour which could be ubiquitous within carbon nanotubes. The He atom is moving between the two ends at a supersonic speed, e.g. from 1.8 to 2.5 Mach, and the oscillation frequency is determined by the diameter, length, and chirality of the tube. The helical motion is attributed to the guidance of potential channels, the signature of the chirality in the potential profiles, and to the hopping effect among these channels. © 2004 The Physical Society of the Republic of China.