Electromagnetic Transport Properties In Quantum Wires And Quantum-dot Arrays

In the mesoscopic system,there are many interesting quantum phenomena and quantum effects which are extensively used to explore devices with novel geometry and principle. So mesoscopic systems have become one of the most active areas of physics in very recent years. Especially, the study on the electromagnetic transport properties of the mesoscopic systems receives much attention. Quantum wires and quantum dots are two typical mesoscopic structures. In this thesis, we study the electromagnetic transport properties of quantum wires and quantum-dot arrays by using the Green's function method. The aim is to find new quantum the effects in these systems and explore the physical mechanisms of the effects, and to supply physical models and theoretical validity in designing novel quantum devices with better properties.The thesis consists of six chapters.In chapter one, we introduce typical mesoscopic structures, their fabrication methods and the characteristics of transport properties in the structures. In chapter two, the lattice Green's function method is introduced, including the representation of Green's function of mesoscopic structures and relevant physics quantities, such as transmission coefficient and local density of state. In chapter three, by using the Green's function method, we study the nonideal effect in the quantum field-effect directional coupler in which two quantum wires are coupled by a finite barrier. Our results indicate that, only for the electrons in a certain region, the complete periodic transfer between two quantum wires can take place. Conductance of the electrons as a function of potential height and barrier length exhibits a periodic and quasi-periodic pattern. While the electrons with energies out of the region, conductance profiles show many irregular oscillations. In addition, finite temperature and asymmetric geometry will decease the transfer efficiency.We study the electromagnetic transport of coupled quantum wires under magnetic field in chapter four. It is found that the double quantum wires coupled by a finite barrier can be an energy filter and current divider. In the parallel direction, the conductance as a function of electron energy show periodic square-wave pattern. The miniband of conductance profile is related with potential height and magnetic strength. It is also found that the structure under magnetic modulation is a better directional coupler. Electrons input from one port of the structure can transmit to any other ports...