Event
MSE Seminar - Prof. Stephen B. Cronin, University of Southern California
Friday, March 13, 2009
1:00 p.m.
Rm. 2108, Chemical and Nuclear Engineering Bldg.
Annette Mateus
301 405 5207
amateus@umd.edu
"One-Dimensional Physics in Individual Suspended Carbon Nanotubes"
Metallic single-walled carbon nanotubes (SWNTs) provide an excellent system for studying interesting one-dimensional physics, including exceptionally strong electron-phonon coupling, Kohn anomalies, ballistic electron transport, and strongly correlated electrons. In this presentation, I will report measurements of nearly defect free, suspended carbon nanotubes under high voltage biases. Raman spectroscopy reveals exceptionally strong electron-phonon coupling, arising from Kohn anomalies, which result in mode selective electron-phonon coupling, negative differential conductance (NDC), and non-equilibrium phonon populations. Due to the extremely long electron lifetimes, we observe a breakdown of the Born-Oppenheimer approximation, as deduced from the gate voltage induced changes in the vibrational energies of suspended carbon nanotubes.
Spatially-resolved temperature measurements of carbon nanotubes under high applied bias voltages reveal a unique thermal conduction mechanism that is quite different from bulk materials, and 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, which are attributed to an insulating state of the strongly correlated electrons.