Electron Transport Properties Of A Quantum Wire With Spin-Orbit Coupling Under Laser Field Irradiation

The electronic transport properties of mesoscopic systems (such as quantum wire, nanowire or quantum dot) have been paid much attention. These properties are not only important basic problems of physics but also have potential applications in the future. The quantum wire and quantum dot etc., will be very important parts of the nanocircuit. As the development of laser technology, the interactions between laser fields and condensed matters become an important scientific problem. It is of particular interest to investigate their influences on electronic transport properties of mesoscopic systems. In this thesis, within the framework of effective-mass free electron approximation and using Keldysh nonequilibrium Green function approach, we investigate theoretically the influences of an external laser field on the electronic structure and transport for a semiconductor hetero-junction quantum wire with Rashba spin-orbit coupling. And some interesting new results have been predicated for the system.The thesis consists of five chapters. In chapter one we briefly introduce the both history and present of the area, which including spin accumulation, spin precession, spin pump, spin filter, spin-polarized transport, spin current and spin-Hall effect based on the spin-orbit coupling in quantum well (or two-dimensional electron gas) of zinc-blend semiconductor heterojunction microstructures. Chapter two describes the formation of semiconductor heterojunctions from the theory of energy bands, and the fabrication as well as the usage of quantum well, quantum wire and quantum dot based on these hetero-junctions. Meanwhile, several typical types of spin-orbit coupling within semiconductors and its heterojunctions have been discussed. Chapter three introduces the nonequilibrium Green function method and its applications in mesoscopic transport, and the widely-employed Keldysh equation of motion with a current formula are induced.The content of chapter four is mainly our work. Using the method of Keldysh equation of motion for nonequilibrium Green function, we have studied the electronic transport properties of a quantum wire irradiated by an external laser field resonant with the quasiparticle transition at low temperatures. In the absence of spin-orbit coupling, the time-averaged conductance of the system shows a feature of absolute negative conductance with photon polarization parallel with the wire direction;when photon polarization perpendicular to the tunneling current direction, the time-averaged conductance indicates astructure of symmetrically distributed peaks. We have further investigated the electronic structure and transport of a Rashba spin-orbit coupling quantum wire under a laser field irradiation. In this case, with the appropriate parameters of the external field (such as frequency Q) and the strength (fc/j) of spin-orbit coupling, spin polarization rate of the system is enhanced greatly and the electronic transport properties are altered significantly. These phenomena are qualitatively and quantitatively discussed.In chapter five, a summary of the work and a outlook of this topic are given.