Conductance of a molecular wire attached to mesoscopic leads: Contact effects

We study linear electron transport through a molecular wire sandwiched betw een nanotube leads. We show that the presence of such electrodes strongly i nfluences the calculated conductance. We find that depending on the quality and geometry of the contacts between the molecule and the tubular reservoi rs, linear transport can be tuned between an effective Newns spectral behav ior and a more structured one. The latter strongly depends on the topology of the leads. We also provide analytical evidence for an anomalous behavior of the conductance as a function of the contact strength.