Electronic properties of semiconductor nanostructures under terahertz radiation

The dynamic conductivity and electromagnetic (EM) absorption of a two dimensional electron-photon system are formulated via calculating the exact time-dependent electronic states and the density matrix of the electron-photon system with its contribution to the electrical current, including electron-THz-photon interaction to all orders. Computations are performed to obtain quantitative results. The exact response function of the magnetically quantized THz driven heterostructure is calculated from the induced charge density. Then collective excitation eigenfrequencies are computed quantitatively. The current in a two dimensional electronic system under a quantizing dc magnetic field and ac electromagnetic radiation field is formulated by determining the exact time-dependent electronic states and density matrix of the system. Under the resonant condition of when photon sideband gap equals Landau level separation and the special case of a weak magnetic field and a low-frequency electromagnetic radiation, the plasmon modes are calculated. Based on a simple physical picture of resonant electron-electromagnetic field coupling, a roton-like plasmon mode and a sound wave are predicted. The dielectric function of a two dimensional electron system with spin orbit coupling is formulated exactly for the special case where the frequency of the electrical field driving the electrical current vanishes.