2008.12.26

31A, Eigineering 2nd Bld, Hongo Campus

Professor Stephen B. Cronin 

Department of Electrical Engineering - Electrophysics

Department of Chemistry

Department of Physics

University of Southern California 

Title：One-Dimensional Electron and Thermal Transport in Suspended Carbon Nanotubes 

Schedule：26th Dec 200812:30 ~ 14:00

Place：31A, Engineering 2nd Bld, Hongo Campus

Map：http://www.u-tokyo.ac.jp/campusmap/cam01_04_03_j.html 

Abstract： 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.  I will report strikingly large variations in the Raman intensity of pristine metallic SWNTs in response to gate voltages. Under high applied bias voltages, we observe mode selective electron-phonon coupling, negative differential conductance (NDC), and non-equilibrium phonon populations.  These phenomena are caused by the exceptionally strong electron-phonon coupling in nanotubes, which arises from Kohn anomolies. I will also report on the 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 thermal conduction mechanism that is quite different from bulk materials.  This mechanism enables these nanotube devices to operate at extremely high power densities.