Electromechanical single electron transistor in strong dissipative structure

In the experiment of electromechanical single electron transistor, two tunneling junctions are not the same completely because of manufacturing processes or quantum effects. We simplify these complexities as an asymmetric-junction device with two unequal initial capacitances. A model system of a single electron transistor with strong dissipation is investigated, where the metal cluster of mechanical motion is coupled to drain and source electrodes. This semiclassical system considers the difference between drain capacitor and source capacitor, simulated by using Monte Carlo methods. The voltage regions are distributed into the efficient-shuttle region and the non-shuttle region by the shuttle mechanism of the island. A symmetric-junction device only works in the efficient-shuttle region. However, both kinds of mechanisms occur in an asymmetric-junction device, where we observe restrained currents and negative differential conductance phenomena.