Tuesday, May 01, 2012

An atlas of carbon nanotube optical transitions


01/05/2012
An atlas of carbon nanotube optical transitions
By: Omar Gómez Rojas ID:139236

Electron–electron interactions are significantly enhanced in one-dimensional systems1, and single-walled carbon nanotubes provide a unique opportunity for studying such interactions and the related many-body effects in one dimension. However, single-walled nanotubes can have a wide range of diameters and hundreds of different structures, each defined by its chiral index (n,m)5, 6, where n and m are integers that can have values from zero up to 30 or more. Moreover, one-third of these structures are metals and two-thirds are semiconductors, and they display optical resonances at many different frequencies. Systematic studies of many-body effects in nanotubes would therefore benefit from the availability of a technique for identifying the chiral index of a nanotube based on a measurement of its optical resonances, and vice versa. Here, we report the establishment of a structure–property ‘atlas’ for nanotube optical transitions based on simultaneous electron diffraction measurements of the chiral index and Rayleigh scattering measurements of the optical of 206 different single-walled nanotube structures. The nanotubes, which were suspended across open slit structures on silicon substrates, had diameters in the range 1.3–4.7 nm. We also use this atlas as a starting point for a systematic study of many-body effects in the excited states of single-walled. We find that electron–electron interactions shift the optical resonance energies by the same amount for both metallic and semiconducting nanotubes, and that this shift (which corresponds to an effective Fermi velocity renormalization) increases monotonically with nanotube diameter. This behaviour arises from two sources: an intriguing cancellation of long-range electron–electron interaction effects, and the dependence of short-range electron–electron interactions on diameter



An atlas of carbon nanotube optical transitions
Kaihui Liu, Jack Deslippe, Fajun Xiao,  Rodrigo B. Capaz, Xiaoping Hong, Shaul Aloni, Alex Zettl, Wenlong Wang, Xuedong Bai, Steven G. Louie, Enge Wang & Feng Wang
Published online 15 April 2012
DOI: 10.1038/nnano.2012.52

1 comment:

preeti said...

Thanks for sharing this beautiful information.Currently i am working on project of nanotechnology which also includes SWNT.This information is very helpful for me.

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