Dynamics of Shuttle Devices
  Much interest has been drawn in recent years to the concept and realization of Nanoelectromechanical systems (NEMS). NEMS are nanoscale devices that combine mechanical and electrical dynamics in a strong interplay. The shuttle devices are a particular kind of Nanoelectromechanical systems. The characteristic component that gives the name to these devices is an oscillating quantum dot of nanometer size that transfers electrons one-by-one between a source and a drain lead. The device represents the nano-scale analog of an electromechanical bell in which a metallic ball placed between the plates of a capacitor starts to oscillate when a high voltage is applied to the plates.   This thesis contains the description and analysis of the dynamics of two realizations of quantum shuttle devices. We describe the dynamics using the Generalized Master Equation approach: a well-suited method to treat this kind of open quantum systems. We also classify the operating modes in three different regimes: the tunneling, the shuttling and the coexistence regime. The characterization of these regimes is given in terms of three investigation tools: Wigner distribution functions, current and current-noise. The essential dynamics of these regimes is captured by three simplified models whose derivation from the full description is possible due to the time scale separation of the particular regime. We also obtain from these simplified models a more intuitive picture of the variety of different dynamics exhibited by the shuttle devices. 
Andrea Donarini