Electromechanics of charge shuttling in dissipative nanostructures

We investigate the current-voltage (I-V) characteristics of a model single-electron transistor where mechanical motion, subject to strong dissipation, of a small metallic grain in tunneling contact with two electrodes is possible. The system is studied both by using Monte Carlo simulations and by using an analytical approach. We show that electromechanical coupling results in a highly nonlinear I-V curve. For voltages above the Coulomb blockade threshold, two distinct regimes of charge transfer occur: At low voltages the system behaves as a static, asymmetric double junction and tunneling is the dominating charge transfer mechanism. At higher voltages an abrupt transition to a new "shuttle" regime appears, where the grain performs an oscillatory motion back and forth between the electrodes. In this regime the current is mainly mediated by charges that are carried on the grain as it moves from one electrode to the other.