Theoretical Studies of Optical Materials

1
Charge Dynamics in Carbon Nanotubes Oleg Prezhdo,
University of Washington, Seattle Award
(CHE-0094012, CAREER)
The unique structural, mechanical, and electronic
properties of carbon nanotubes (CN) have
suggested a variety of applications. Numerous
time-resolved experiments have revealed
intriguing features of the electron-phonon
relaxation in CNs in response to external
stimuli. A clear understanding of the electron
and hole dynamics is critical to the development
of such devices as logic gates, optical switches,
and lasers. The observed superconductivity,
conductivity and energy loss in nanowires and
field-effect transistors depend on the
charge-phonon interaction, scattering and
relaxation in CNs. With the experimental data in
hand, we have initiated ab initio modeling of the
observed phenomena in real-time and at the
atomistic level of detail. Our first results for
the electron and hole relaxation from the second
van Hove singularities to the Fermi energy in the
smallest semiconducting CN have reproduced the
characteristic subpicosecond experimental
timescale and have revealed a number of
surprising features. Despite a lower density of
states, the electrons relax faster than the
holes. The hole dynamics are more complex than
the electrons. The relaxation is primarily
mediated by the C-C stretching G-phonons. In
addition, the holes couple to the lower frequency
breathing modes and decay over multiple
time-scales.
B. F. Habenicht, C. F. Craig, O. V. Prezhdo,
preliminary results