A molecular wire sandwiched between nanotube leads: analytic results for the conductance

Analytic results for the conductance of a molecular wire attached to mesoscopic tubule leads are obtained. They permit to study linear transport in presence of low dimensional leads in the whole range of parameters. In particular contact effects can be addressed in detail. By focusing on the specificity of the lead–wire contact, we show that the geometry of this hybrid system supports a mechanism of channel selection, which is a distinctive hallmark of the mesoscopic nature of the electrodes. The nanometer length domain, the fate of the transistor integration length, is unavoidably rising a new variety of phenomena concerning the rôle of quantum effects on electronics at the molecular scale [1]. Although molecular materials for electronics are already realized [2, 3, 4, 5], real molecular scale electronic devices [6, 7, 8] still have to cope with challenges in utilization, synthesis, and assembly [9]. The idea of molecular rectification proposed since 1974 [10] found experimental evidence only 20 years later [11, 12]. Concerning theory, conventional methods employed for characterizing transport properties in microelectronic devices, such as the Boltzmann equation [13], can no longer be applied at the molecular scale. Here transport properties have to be calculated by using full quantum mechanical approaches. Electron transmission through molecular and supramolecular interfaces was already the object of intensive theoretical investigation in the last decade due to the electron transfer phenomena underlying the use of scanning tunneling microscopes. More recently, studies of transmission properties of a molecular junction contacted to metallic leads [14, 15] have intensified the interest in the basic mechanisms of conduction across molecular bridges. In a parallel development the use of carbon nanotube (CNT) networks has been the focus of intense experimental and theoretical activity as another promising direction for building blocks of molecular circuits [16, 17]. Carbon nanotubes are known