Dynamics And Transport Properties Of Quantum Dot Systems

This dissertation mainly includes three parts. The first part presents the theoretical research on dynamics property of the time-dependent double quantum dots system. The results of this part are mainly obtained by using the tight-bonding Hubbard model. The second part discusses the electronic inelastic transport through a quantum dot in the presence of the electron-electron interaction by using the Keldysh nonequilibrium Green function approach. In the third part, we study electronic transport properties of an Aharonov-Bohm ring with embedded coupled double quantum dots connected to two electrodes in a symmetrical parallel configuration in the presence of strong interdot Coulomb interaction by using the Keldysh nonequilibrium Green function approach.The first part is composed of seven subsections. The first subsection simply introduces quantum dots system. In the second subsection, we introduce the background of the study on the time-dependent mesoscopic system. The development of laser technologies open the doorway for studying the new quantum effects in nonlinear quantum systems which interact with strong electromagnetic field. In the third subsection, we introduce a good approach (Floquet theory) to study of quantum systems with their Hamiltonian being a periodic function in time. In the 4th subsection, we study the dynamics of the two interacting electrons in an asymmetric double coupled quantum dot under an ac electric field. The numerical results demonstrate that the dynamical localization and Rabi oscillation still excite in the system. In the 5th subsection, we investigate the dynamical behaviors of an interacting electron - hole pair in a double coupled quantum dot molecule under an ac electric field. We theoretically analyze the phenomenon of localization of an exciton in the quantum system under the strong Coulomb interaction, and indicate the conditions that dynamical localization occurs. The attractive Coulomb interaction plays an important role in forming the entangled states of the system. In the 6th subsection, we theoretically analyze the dynamical behaviors of an interacting electron - hole pair in a double coupled quantum dot molecule in radiation pulses. It is found the maximally entangled Bell states can be prepared when a resonant transfer occurs between two localized states. A summary and prospec-tion are given in 7th subsection. The second part includes 8 subsections. The first subsection briefly introduces the background of the study on the transport through the quantum dot system. In the second subsection, the definitions of Green functions are introduced. The third subsection introduces three exactly solvable models : free-particle model, resonant-level model and Einstein model. In the 4th subsection, we introduce the nonequilibrium keldysh technologies, which is an important approach to study the transport properties of the time-dependent or time-independent quantum dots system. Photon- assisted tunneling processes are introduced in the 5th subsection. In the 6th subsection a phonon-assisted model is given. The 7th subsection is the important part in the second chapter. We study the low-temperature inelastic transport properties of a single quantum dot with the on-site Coulomb repulsive interaction, the electron-phonon interaction and the electron-photon interaction by using the nonequilibrium Green function(NEGF) approach and the canonical transformation. The time-averaged occupation number, the time-averaged differential conductance and time-averaged current are calculated self-consistently in the quantum dot. The variation in the differential conductance with the frequency of the external field and the incident electron energy is presented. It is found that the two kinds of phonon-emission peaks may coexist in the time-averaged differential conductance spectrum due to the charge accumulations. In the last subsection the summary and prospection are present.The third part includes 6 subsections. The first subsection briefly introduces the background of the study on the transport through the double quantum dots system. In the second subsection, we give a model consists of two single-level coupled quantum dots attached in a parallel configuration to the leads. In the third subsection, we calculate the Green's function of the two dots by using the standard equation-of-motion technique. In the 4th subsection, we give tunneling current formula by using the Keldysh Green function. Numerical results and discussion are given in the 5th subsection. The summary and prospect are written in the last subsection.