Electrons Transport Property Of The Mesoscopic Systems

In this work, we have made a detailed investigation on single electron transportproperty in mesoscopic systems and the magnetoresistance effect in these structures,which owns great potential application in future devices. On the one hand,wediscover new effects in known mesoscopic structures; on the other hand,we expect tosupply physical model and make theoretical validity for device design based on thesestructures. 1. The ballistic transport of the two dimensional electron gas modulated by the magnetic field has been studied. The results show that the transmission coefficient influenced by the periods of the magnetic fields, and with the increase of the periods, resonant peaks show more complicated resonance, and also been enhanced. We also studied the conductance of the parallel and the antiparallel alignments, respectively. It is found that the conductance also appears the resonance and the features are same as that of the transmission coefficient. 2. We investigated a giant magnetoresistance effect of two-dimensional electron gas systems in a periodically modulated magnetic field. It is found that the magnetoresistance (MR) ratio of the present system shows strong dependence on the space of the potentials. The calculated results also show that the larger magnetoresistance effect can be obtained in the symmetric magnetic structures. Furthermore, with the number of periods increasing, the MR ratio shows oscillations and the system with odd periods is always larger than that with even ones in a given structure. Meanwhile, the peaks of the MR ratio locate at a specific Fermi energy for the given space of potentials. 3. Two dimensional electron gas systems modulated by lateral magnetic superlattieces are proposed and the magnetoresistance effect related is described here. It is found that the magnetoresistance ratio of the given structures depends - II -摘 要strongly on the uniform magnetic field, and the peaks of the MR ratio depressedlinearly with the increase in the magnetic field. This interesting feature may leadsto new practical linear magnetoresistance (LMR) devices.