Electronic Transport Properties Of Quasi-one Dimensional Quantum Structure: Green's Function Approach

Quasi-one dimensional quantum structures such as quantum wire,waveguide are forefront in condensed matter physics. Recently, theyhave received increasing interests due to there existing in thesesystems a great deal of novel and marvelous physics properties andprospective potential applications. In this thesis, we study theelectronic transport properties through quasi-one dimensionalquantum systems. The aim is to explore the physical mechanisms ofthe found new effects in these systems, and to supply physical modelsand theoretical validity in designing novel quantum devices withbetter properties. The thesis consists of five chapters. In chapter one, we introducefabrication methods of typical mesoscopic structures as well as thecharacteristics of transport properties. In chapter two, the lattice Green's function is introduced,especially recursive Green's function method. Comparing with othernumerical methods, the lattice Green's function is much convenient totreat problems with magnetic modulation and disorders, of which therecursive Green's function method can effectively resolve big-scalesystems by dividing them into several parts. Chapter three concerns electron transport across a quantum wireembedding a saw-tooth quantum dot or a finite-length saw-toothsuperlattice using RGF method. It is found that the transmission 3陈元平 湘潭大学硕士毕业论文across the structure is closely associated with the size of quantum dot.When the quantum dot is subjected to a weak magnetic field, quantuminterference in quantum dot becomes more pronounced. At large fieldmodulation, quantization plateau of transmission coefficient appears.As a quantum wire embeds a finite-length saw-tooth superlatticeconsisting of n quantum dots, the resonant peak splitting is (n-1)-foldexcept quasibound peak splitting is n-fold at zero field. In addition,the presence of weak magnetic field induces the number of the secondresonant peak splittings increases one. By developing a lattice Green's method, we calculate theelectronic transport properties of T-shaped quantum wires underpotential modulation in chapter four. The influence of potentialmodulation between vertical leads and parallel quantum wire onelectronic transport across one and two-coupled T-shaped quantumwire(s) is studied. It is shown that, for a T-shaped quantum wire, thepotential induces a dip-peak couple structure in the conductancecurves for parallel and bend transport. The modulation of the potentialthickness makes the dip-peak couple more pronounced and increasesthe number of dip-peak couple. For two coupled T-shaped quantumwires, various conductance profiles can be obtained by the potentialmodulation on coupled T-shaped quantum wires. In addition, thepotential modulation on transport properties of three-terminalquantum dot is also discussed. The last chapter presents a conclusion of this thesis and someprospects for this investigation.