Electron transport of a quantum wire containing a finite-size impurity   under THz electromagnetic field illumination
  We theoretically investigate the electron transport properties for a semiconductor quantum wire containing a single finite-size attractive impurity under an external terahertz electromagnetic field illumination in the ballistic limit. Within the effective mass free-electron approximation, the scattering matrix for the system has been formulated by means of a time-dependent mode matching method. Some interesting properties of the electron transmission for the system have been shown through a few groups of numerical examples. It is found that in the case of the comparative stronger field amplitude and the frequency resonant with the two lowest lateral energy levels in the impurity region, the field-induced intersubband transition dominates the process as if without the impurity. And there is a step-arising on the transmission as a function of the incident electron energy. However, in the case of lower field amplitude and the non-resonant frequencies both multiple symmetry Breit-type resonance peaks and asymmetry Fano-type dip lines appear in the electron transmission dependence on the incident energy due to the presence of the impurity and the external field. Therefore, within certain energy range the transmission as a function of the field frequency and/or field amplitude shows a rich structure. Moreover, the transmission dependence on the strength and size of the impurity is also discussed. It is suggested that these results mostly arise from the interplay effects between the impurity in a quantum wire and the applied field. 
Guanghui Zhou, Yuan Li, Fang Cheng and Wenfu Liao