Direct Determination of Absolute Electron-Phonon Coupling Strengths in Carbon Nanotubes
Y. Yin, A. Walsh, S. Cronin, M.S. Ünlü, B.B. Goldberg and A.K. Swan
Boston University, US
single wall carbon nanotube, electron-phonon coupling, Chirality dependence
We present for the first time determination of the magnitude of e-phonon coupling matrix elements and their diameter and chirality dependence for single walled carbon nanotubes.
The electron-phonon coupling strength is a fundamental parameter in all optical and transport properties of solid state systems, yet is often difficult to determine directly from experiment. We perform resonant Raman measurements on small ropes or individual single walled carbon nanotubes suspended across etched trenches in air, repeated for many different tubes with different diameters and chiralities. The strengths of the electron-phonon coupling for the radial breathing phonon modes are extracted directly from comparisons with the resonant profiles of the various modes from the same carbon nanotube. Our data dramatically support the chirality and radial dependence suggested by tight binding calculations of the e-phonon coupling strengths by Goupalov et al. In addition to understanding ballistic transport, these results elucidate quantitative analysis of the nanotube distributions, since one can now separate the effects of the strongly resonant nature of the optical transitions from the electron-phonon coupling strength and yield accurate relative distributions of nanotube species from ensemble measurements.
1. S.V. Goupalov, B.C. Satishkumar and S.K. Doorn, submitted.
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Nanotech 2006 Conference Program Abstract