Coherent Phonon Dynamics in Single-Walled Carbon Nanotubes

Understanding how electrons and phonons relax in energy and momentum is one of the current goals in carbon nanotube spectroscopy as well as an important step towards developing novel electronic and optoelectronic devices based on carbon nanotubes. Recent ultrafast pump-probe spectroscopy studies of single-walled carbon nanotubes (SWNTs) have successfully detected coherent phonon dynamics, but the dominant dephasing mechanism that occurs with decoherence of phonon mode oscillations has yet to be understood. Our previous work demonstrating ultrafast coherent phonon spectroscopy of the radial breathing mode (RBM) of semiconducting SWNTs provided a powerful method for determining phonon energies in an ensemble of SWNTs. We now extend our previous studies to provide new insight into the dephasing mechanisms of coherent phonons in SWNTs. Here, we systematically investigated the temperature, polarization, and wavelength dependence of coherent phonon dephasing times, amplitude, and frequency for various types of nanotube film and solution samples.