Raman spectra and electrical conductance of individual, pristine, suspended, metallic single-walled carbon nanotubes are measured under applied gate potentials. The G- band is observed to downshift with small applied gate voltages, with the minima occurring at EF = +/- 1/2 Ephonon, contrary to adiabatic predictions. A subsequent upshift in the Raman frequency at higher gate voltages results in a 'W'-shaped Raman shift profile that agrees well with a non-adiabatic phonon renormalization model. This behavior constitutes the first experimental confirmation of the theoretically predicted breakdown of the Born-Oppenheimer approximation in individual single walled carbon nanotubes.
@article{arxiv.0901.2947,
title = {Direct Observation of Born-Oppenheimer Approximation Breakdown in Carbon Nanotubes},
author = {Adam W. Bushmaker and Vikram V. Deshpande and Scott Hsieh and Marc W. Bockrath and Stephen B. Cronin},
journal= {arXiv preprint arXiv:0901.2947},
year = {2015}
}