The Transport Properties And Dynamics In Coupled Double Quantum Dot Ring

Mesoscopic nano-systems are one of the most active study fields in condensed matter physics. As an important mesoscopic system, the transport properties of the quantum dot have attracted much attention in theoretical and the experimental studies. In this thesis, based on non-equilibrium Green's function method and the Floquet theory we investigate theoretically the transport properties of coupled quantum dot ring driven by an external field. Our purpose to reveal the effect of the dot number in the ring and the dot-lead coupling and to explore the physical mechanisms of the new effects in coupled quantum dot ring systems through theoretical investigation; and to provide theoretical basis for the nano-device design.Firstly, we introduce the main characteristics and the application of quantum dot system, and the non-equilibrium Green's function method and the Floquet theory. Then, using the non-equilibrium Green's function method, we study dynamical localization effect of coupled quantum dot ring driven by an ac magnetic field. We found that when the ratio of the magnetic flux to the total quantum dots number is a root of the zeroth order Bessel function, the collapse of the quasi-energy spectrum of the system occurs and a minimum of the average current appears, the electron is localized in a quantum dot. The dynamical localization effect is strengthened as the quantum dot number increasing, and it is weakened as the dot-lead hopping rate increasing. Finally, we studied the transport properties of triple coupled quantum dot ring driven by AC electric field and DC magnetic field. The results show that:AC electric field can control the effective tunneling between two quantum dots and thus control the transport current.