Excitons Insensitive to Environment

Screening of Excitons in Single, Suspended Carbon Nanotubes

A.G. Walsh, et al.

Nanoletters 7, 1485--1488 (2007)

URL: http://pubs.acs.org/cgi-bin/abstract.cgi/nalefd/2007/7/i06/abs/nl070193p.html



This group from Boston University has investigated the binding energy of excitons in nanotubes as a function of the dielectric constant of the environment. They repeated photoluminescence measurements on nanotubes in dry air, humid air, and water. In general, they find that the binding energy is not very sensitive to changes in the dielectric environment. The binding energy only changes by a couple tens of meV between dry air and water.

The theoretical model they use is a 1D interaction of the form V / ( |z| + Z ). Surprisingly, they find that the parameter Z scales linearly with the dielectric constant! They claim this model was solved exactly in 1959. I’m going to track down that reference. With the exact solution and scaling relation for Z, they are able to reproduce the scaling of their data as well as a scaling relation reported by Perebeinos a couple years ago.