Kondo Effect In Quantum Dots Study Shuttle Systems

In this dissertation, by employing the equation of motion method for the nonequilibrium Green’s function, we investigate the density of states of the quan-tum dot and the transport properties on the quantum dot-electrode system. With the increase of the coupling between the dot and the electrode, the density of states of the quantum dot changes from the Coulomb-blockade pattern to Kondo pattern. Furthermore, we investigate the density of states of the quantum dot in the electron shuttle system and show how the density of the dot change with the frequency of mechanical vibration.In chapter1, we first state the Coulomb blockade effect and the simple electron shuttle system and some electronic shuttle devices, and also explain some features of the Green’s function.In chapter2, we show the Coulomb blockade effect and Kondo effect in the electron transport in a quantum dot-electrode system. With the increase of the coupling between the dot and the electrodes, the density of states of the quantum dot changes from the Coulomb-blockade to Kondo-like pattern. And we analyze how the current features in the transportation system varying with the increase of the oscillation frequency of the dot.In chapter3, we show the Coulomb blockade effect and Kondo effect in the shuttle system. Employing the equation of motion method for the nonequilibrium Green’s function, we show that the oscillation of the dot, i.e. the time-dependent coupling between the dot’s electron and the reservoirs can destroy the Kondo effect. With the increase of the oscillation frequency of the dot, the density of states of the quantum dot shuttle changes from the Kondo-like to Coulomb-blockade pattern. Increasing the coupling between the dot and the electrodes may partly recover the Kondo peak in the spectrum of the density of states. All the results lay the fundamental for the further study of transport properties of quantum dot shuttle system.In chapter4, the summary and forecasting.