Nanomechanical oscillations in a single-C60 transistor

Abstract

The motion of electrons through quantum dots is strongly modified by single-electron charging and the quantization of energy levels^1,2. Much effort has been directed towards extending studies of electron transport to chemical nanostructures, including molecules^3,4,5,6,7,8, nanocrystals^{9,10,11,12,13} and nanotubes^14,15,16,17. Here we report the fabrication of single-molecule transistors based on individual C₆₀ molecules connected to gold electrodes. We perform transport measurements that provide evidence for a coupling between the centre-of-mass motion of the C₆₀ molecules and single-electron hopping¹⁸—a conduction mechanism that has not been observed previously in quantum dot studies. The coupling is manifest as quantized nano-mechanical oscillations of the C₆₀ molecule against the gold surface, with a frequency of about 1.2 THz. This value is in good agreement with a simple theoretical estimate based on van der Waals and electrostatic interactions between C₆₀ molecules and gold electrodes.