Fabry - Perot interference in a nanotube electron waveguide

Abstract

The behaviour of traditional electronic devices can be understood in terms of the classical diffusive motion of electrons. As the size of a device becomes comparable to the electron coherence length, however, quantum interference between electron waves becomes increasingly important, leading to dramatic changes in device properties^{1,2,3,4,5,6,7,8}. This classical-to-quantum transition in device behaviour suggests the possibility for nanometer-sized electronic elements that make use of quantum coherence^1,2,7,8. Molecular electronic devices are promising candidates for realizing such device elements because the electronic motion in molecules is inherently quantum mechanical^9,10 and it can be modified by well defined chemistry^11,12,13. Here we describe an example of a coherent molecular electronic device whose behaviour is explicitly dependent on quantum interference between propagating electron waves—a Fabry–Perot electron resonator based on individual single-walled carbon nanotubes with near-perfect ohmic contacts to electrodes. In these devices, the nanotubes act as coherent electron waveguides^14,15,16, with the resonant cavity formed between the two nanotube–electrode interfaces. We use a theoretical model based on the multichannel Landauer–Büttiker formalism^17,18,19 to analyse the device characteristics and find that coupling between the two propagating modes of the nanotubes caused by electron scattering at the nanotube–electrode interfaces is important.