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arXiv · 1408.0672

Origin of coherent G band phonon spectra in single wall carbon nanotubes

A. R. T. Nugraha·E. H. Hasdeo·G. D. Sanders·C. J. Stanton·R. Saito
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Abstract

Coherent phonons in single wall carbon nanotubes (SWNTs) are observed as oscillations of the differential absorption coefficient as a function of time by means of pump-probe spectroscopy. For the radial breathing mode (RBM) of a SWNT, the coherent phonon signal is understood to be a result of the modulated diameter-dependent energy gaps due to the coherent RBM phonon oscillations. However, this mechanism might not be the dominant contribution to other phonon modes in the SWNT. In particular, for the G band phonons, which correspond to bond-stretching motions, we find that the modulation of the interatomic dipole matrix element gives rise to a strong coherent G band phonon intensity comparable to the coherent RBM phonon intensity. We also further discuss the dependence of coherent G band and RBM phonon amplitudes on the laser excitation pulse width.

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A. R. T. Nugraha, E. H. Hasdeo, G. D. Sanders, C. J. Stanton, R. Saito. 2014-08-04. Origin of coherent G band phonon spectra in single wall carbon nanotubes. https://doi.org/10.1103/physrevb.91.045406

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