Single Electron Effects in a Carbon Nanotube Electromechanical Oscillator

We have fabricated suspended, doubly clamped, carbon nanotube (NT) transistors to investigate the low temperature coupling between mechanical vibration of the NT and single electron effects. At low temperatures of 0.3K to 4.2K, the NT behaves as a quantum dot. The NT quantum dot displays Coulomb oscillations in the conductance by sweeping a gate voltage. Mechanical vibrations are induced in the NT by applying a high frequency AC voltage relative to the gate [1]. The nonlinear conductance of the Coulomb oscillations can be used as a mixer to detect the NT's own motion. We find that the mechanical resonances of the NT are influenced by the Coulomb oscillations. We observe a dip in the resonance frequency and a dip in the quality factor as the gate voltage is swept through a Coulomb oscillation. We attribute these dips to the forces on the NT from the hopping of single electrons on and off the NT as it moves with respect to the gate. [1] V. Sazonova, Y. Yaish, H. Ustunel, D. Roundy, T.A. Arias, and P.L. McEuen, Nature 431, 284-287 (2004)