Aharonov-Bohm effect on impurity-bound excitons in semiconducting carbon nanotubes

Abstract

We study the Aharonov-Bohm effect on exciton absorption spectra in semiconducting carbon nanotubes with an impurity in an effective-mass theory. In the presence of an impurity potential, there are two impurity-bound exciton states, one is dark and the other is bright. The dark impurity-bound exciton becomes brightened with increasing a magnetic flux through the cross section. The energy level of the bright impurity-bound exciton shows a blueshift in the magnetic flux dependence for a long-range impurity; in contrast, it shows a redshift for a short-range impurity, due to an enhancement of the coupling between intra- and inter-valley excitons. This suggests that the magnetic flux dependence can distinguish the range of the impurity potential and the strength of the inter-valley coupling of excitons.