Shot noise and electron-phonon coupling in carbon nanotubes

Abstract Submitted to the

Shot noise and electron-phonon coupling in carbon nanotubes

Fan Wu¹, Taku Tsuneta¹, Mikko Paalanen¹, Taihong Wang², and Pertti Hakonen¹

¹ Low Temperature Laboratory, Helsinki University of Technology, Espoo, Finland
² Institute of Physics, Chinese Academy of Sciences, Beijing, China
Contact e-mail: pjh@neuro.hut.fi

We have investigated shot noise in individual SWNTs and MWNTs at 4.2 K over the frequency range 650 - 850 MHz. At small currents, our SWNT samples display a Fano-factor of F ~ 1, reminiscent of a single tunnel junction behavior. At large bias, we observe a strong reduction in the Fano factor both in SWNTs and MWNTs. Using the theory by Nagaev, we may interprete this noise suppression as originating from inelastic processes caused by electron-phonon scattering, both due to acoustic and optical phonons. We find that the electron-phonon scattering length in a SWNT decreases rapidly above 0.1 V and it is about 5 nm at a bias of 0.5 V. In disordered MWNTs, we observe a Fano-factor of ~ 0.1, clearly less than expected for diffusive conductors.

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