Electronic Transport Properties Of An Impurity Quantum Wire Under THz Electromagnetic Field Illumination

The properties of electronic transport of quantum wire have been intensively studied. These properties are not only significant basic problems of physics but also have potential application in the future. The mesoscopic system, such as quantum wire, will be very important parts of the quantum nanocircuit. As impurities, intentional or not, are unavoidable, it is of particular interest to investigate their influence. The existence of impurities will affect the properties of electronic transport and the quality of nanodevice. It is interested to investigate the effect of impurities on the transport properties of quantum wire. Using Landauer-Buttiker transport theory and the scattering matrix method in this thesis we study the influence of a single finite-size attractive impurity on the electron transport of a semiconductor quantum wire under a terahertz electromagnetic illumination. All these studies are within the framework of free electron.The thesis consists of four chapters. In chapter one we briefly introduce 2-dimensional electron gas within Al_xGa_1-xAs/GaAs heterojunctions and quantum wire based on it, the theory of electronic transport in mesoscopic physics and the scattering matrix method.Chapter two investigates the electronic transport properties of a straight quantum wire with a single finite-size attractive impurity partly irradiated by an transversely polarized THZ electromagnetic wave. We have solved the time-dependent Schrodinger equation by using time-dependent mode matched scattering matrix method. We obtain the following conclusions:1.A transmission step-like structure has been predicted when the field frequency of the external field is resonant with the separation of lateral levels of the quantum wire. The single impurity almost do not changing the transmission behavior in this case. 2.The transmission exhibits a clear signature in the form of a dip in the case of non-resonant when the values of the field frequency and the field amplitude are proper. Both of the second mode of the two regions with and without illumination begin to become propagating modes associating with the location of the dip. That is to say, there is a new channel to open so that the transmission sharply increase to nearly 1. Prom the aspect of physics, the electron can transit to a quasibound state by emitting a photon. 3.There exits Breit-Wigner resonance due to the interference of the forward and backward electron waves.In chapter three, we investigate the effect the parameters of external field and the...