Interband Excitons in Carbon Nanotubes

Polarized Photoluminescence Excitation Spectrum of Single-Walled Carbon Nanotubes

J. Lefebvre and P. Finnie

PRL 98, 167406 (2007)

URL: http://link.aps.org/abstract/PRL/v98/e167406

The authors report photoluminescence measurements in carbon nanotubes. They present data for light polarized parallel to the nanotube axis, similar to previous experiments. However, this paper is the first I've seen to probe the photoluminescence spectrum of light polarized perpendicular to the nanotube axis.

Louie, et alii published a paper in 1995 --- a theoretical investigation of the polarizability of carbon nanotubes. They predict the response to light polarized along the nanotube axis to be an order of magnitude larger than for perpendicular polarization. This prediction seems to have been borne out in experiments, especially the one reported in this Letter.

The authors see familiar patterns of absorption at E22 and emission at E11, plus new data on the E12 peak (which is identical to the E21 peak, according to the authors). They claim to see dependence on the chiral angle that has not been included in an analytic theory yet.

Overall, I think the authors have done an excellent job collecting and presenting their data. However, I am confused by their analysis. They report two sidebands of the E11 peak, but it seems they have devoted far too much space to what these sidebands are not. After four paragraphs, I still don't know what the author believe the sidebands are.

This is definitely a good paper for my "Excitons: Experiments" folder. The data presented here might be relevant to the next phase of my research.