Fabry-Perot interference in a nanotube electron waveguide

The behaviour of traditional electronic devices can be understood in terms of the classical diffusive motion of electrons. As the size of a device bec omes comparable to the electron coherence length, however, quantum interfer ence between electron waves becomes increasingly important, leading to dram atic changes in device properties(1-8). This classical-to-quantum transitio n in device behaviour suggests the possibility for nanometer-sized electron ic elements that make use of quantum coherence(1,2,7,8). Molecular electron ic devices are promising candidates for realizing such device elements beca use the electronic motion in molecules is inherently quantum mechanical(9,1 0) and it can be modified by well defined chemistry(11-13). Here we describ e an example of a coherent molecular electronic device whose behaviour is e xplicitly dependent on quantum interference between propagating electron wa ves-a Fabry-Perot electron resonator based on individual single-walled carb on nanotubes with near-perfect ohmic contacts to electrodes. In these devic es, the nanotubes act as coherent electron waveguides(14-16), with the reso nant cavity formed between the two nanotube-electrode interfaces. We use a theoretical model based on the multichannel Landauer-Buttiker formalism(17- 19) to analyse the device characteristics and rnd that coupling between the two propagating modes of the nanotubes caused by electron scattering at th e nanotube-electrode interfaces is important.