Abstract
Effects of environmental dielectric screening on excitons in carbon nanotubes are studied within a k · p scheme and a continuum model. They are shown to be sensitive to the effective distance between the nanotube and the dielectric medium relative to the diameter. For material surrounding the nanotube, the band gap decreases with the increase of the dielectric constant, but the energy of the ground exciton exhibits only a slight decrease for effective distance comparable to interlayer spacing of bulk graphite. The binding energy of excited exciton states disappears rapidly. For dielectric material inside the nanotube, effects are much weaker and excited exciton states remain as bound states even for very large dielectric constant.
Highlights
A carbon nanotube has characteristic optical properties.The absorption of light polarized perpendicular to the axis is suppressed and the optical absorption is dominated by parallel polarization
Effects of environmental dielectric screening have been theoretically studied within the k
cylindrical material inserted in a nanotube
Summary
The absorption of light polarized perpendicular to the axis is suppressed and the optical absorption is dominated by parallel polarization. The exciton effect plays a decisive role in optical absorption and emission. The purpose of this paper is to study effects of environmental dielectric screening on electronic and optical properties of nanotubes based on a k p scheme. Important optical properties of nanotubes were first clarified based on the lowest order k p scheme for describing electronic states in graphene.1–8) it was used for the demonstration of the suppression of the absorption of light polarized perpendicular to the axis due to a strong depolarization effect9,10) and the role of interaction effects on the band gap and on excitons.). Tight-binding models including exciton effects were proposed.23–28) There have been various other proposals of description of excitons.29–34)
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