Phonon wave-packet scattering and energy dissipation dynamics in carbon nanotube oscillators
MVD Prasad and B Bhattacharya, JOURNAL OF APPLIED PHYSICS, 118, 244906 (2015).
Friction in carbon nanotube (CNT) oscillators can be explained in terms of the interplay between low frequency mechanical motions and high frequency vibrational modes of the sliding surfaces. We analyze single mode phonon wave packet dynamics of CNT based mechanical oscillators, with cores either stationary or sliding with moderate velocities, and study how various individual phonons travel through the outer CNT, interact with the inner nanostructure, and undergo scattering. Two acoustic modes (longitudinal and transverse) and one optical mode (flexural optical) are found to be responsible for the major portion of friction in these oscillators: the transmission functions display a significant dip in the rather narrow frequency range of 5-15 meV. We also find that the profile of the dip is characteristic of the inner core. In contrast, radial breathing and twisting modes, which are dominant in thermal transport, display ideal transmission at all frequencies. We also observe polarization dependent scattering and find that the scattering dynamics comprises of an oscillating decay of localized energy inside the inner CNT. This work provides a way towards engineering CNT linear oscillators with better tribological properties. (C) 2015 AIP Publishing LLC.
Return to Publications page