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Dynamics of Shuttle Devices

Much interest has been drawn in recent years to the concept and realization of Nanoelectromechanical systems (NEMS). NEMS are anoscale 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 lectromechanical bell in which a metallic ball placed between the plates of a capacitor starts to oscillate when a high voltage is applied to the lates.

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.

Mostra/Nascondi contenuto.
Chapter 1 Introduction In this chapter we give a short introduction to the world of nanoelectrome- chanical systems. We then focus our attention on a particular kind of device called electron shuttle. We sketch the basic operating regime and give an overview of the different theoretical models that have been proposed to de- scribe the dynamics of such devices. We report on the two main realizations of shuttle devices and close the chapter with an outline of the contents of this thesis. 1.1 NEMS Much interest has been drawn in recent years on the concepts and realiza- tion of Nanoelectromechanical systems (NEMS). NEMS are nanoscale devices that combine mechanical and electrical dynamics in a strong interplay. This property makes them interesting both from a technological and fundamental point of view. They are extremely sensitive mass and position detectors. Due to their very high mechanical frequency one can even think of using them as the basis for new form of mechanical computers. From the point of view of fundamental research they represent extremely good tools to probe directly the basic quantum mechanical laws. They could represent the first man-made structures on which the mechanical zero point fluctuation can be detected. They also rise the question on the limiting dimension for persis- tence of mechanical coherence. In general one of the fascinating aspects of these objects is their mesoscopic character: they share with the macroscopic world the large number of atoms of which they are made (typically of millions of atoms) but on the other hand their behaviour is (or should be) already significantly determined by quantum mechanics. 11

Tesi di Dottorato

Dipartimento: Department if Micro and Nanotechnologies

Autore: Andrea Donarini Contatta »

Composta da 158 pagine.

 

Questa tesi ha raggiunto 321 click dal 01/02/2005.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.