Professor Stephen B. Cronin
Department of Electrical Engineering - Electrophysics
University of Southern California

 

One-Dimensional Phenomena in Suspended Carbon Nanotubes

Individual suspended carbon nanotubes provide an ideal system for studying low-dimensional phenomena, including Kohn anomalies, exceptionally strong electron-phonon coupling, ballistic electron transport, and strongly correlated electrons. In this presentation, the ballistic electron transport in nearly defect-free, suspended carbon nanotubes is investigated using micro-Raman spectroscopy. Under high applied bias voltages, we observe mode selective electron-phonon coupling, negative differential resistance (NDR), and non-equilibrium phonon populations. These phenomena are caused by the exceptionally strong electron-phonon coupling in nanotubes, which arises from Kohn anomalies. I will also report on the breakdown of the Born-Oppenheimer approximation, resulting from the extremely long electron lifetimes. Spatially-resolved temperature measurements of these nanotubes under high applied bias voltages reveal a thermal conduction mechanism that is quite different from bulk materials. This mechanism enables these nanotube devices to operate at extremely high power densities. Lastly, I will report strikingly large variations in the Raman intensity of pristine metallic SWNTs in response to gate voltages.