Electron Transport Through Mesoscopic System

In this work we have made a detail investigation on the electronic transport properties through mesoscopic system. Our aim is to explore the physical mechanisms of the new effects in mesoscopic systems, and to supply physical models and make theoretical validity in designing novel quantum devices with better properties.First, A general recursive Green's function method, which can be used for systems with arbitrary shapes and connection conditions in the same footing, is proposed based on the Dyson's equation. It is a generalized method of the conventional recursive Green's function method, and can be applied widely.Then, we study the general transmission properties and the effects of strong correlative interactions between electrons in a lattice of quantum dots. The effects of magnetic impurities and temperature on the transmission properties in this system are investigated. Moreover, it is found that there exists a metal to antiferromagnetic-uisulator transition, which is driven by strong correlative interactions, around the half-filling in this system. Our numerical results explain, for the first time, that the Mott-insulator state is caused by the antiferromagnetic spin density wave.The resonant tunneling in an mesoscopic ring with a quantum dot embedded in one of its arms is also investigated. The system can be divided into two parts: the small dot and its big complementary partner (CP) which is attached by two ideal leads. A complete transmission mechanism, considering both the resonance of the dot and the interference effect, is presented. The transmission character is basically dominated by the CP when there is no resonance in the transmission through the dot. As a consequence, the experimental results, the phase features for conductance peaks, are well explained by an one-dimensional noninteracting model. Moreover, a semi-classical scatterer model is applied to study this system. With a proper scattering matrix, which describes the junctions between the leads and the ring, we show anahtically that the quantum interference effects and the resonant tunneling through the quantum dot dominate the transmission. The dependence of the total transmission coefficient on the properties of the quantum dot is also presented and agrees well with the experimental results.Last, The properties of coupled quantum dots are studied theoretically. We findthat by introducing multiple coupling paths, rather than the single tunneling path used in previous studies, the effects of bond direction on an artificial molecule can be simulated. The effects of parities of the orbits on the interactions between them are revealed. The electron transmission properties in this system is also given. Because the components of this molecule, coupled quantum dots, are controllable, this system is ideally suited for fundamental studies in a regime that is inaccessible on real atoms. Our study also examine the electronic transport property of the system, which could be checked experimentally. The system herein reported is both theoretically and experimentally interesting, not only because it is molecular-like. but also because it is a controllable system. Much novel information about molecules and the interactions among atoms may be revealed and used in further analysis and experiments.