Coupled Quantum Dots, Carrier Dynamics Behavior. External Field

We study the dynamical behaviors of two elections and electron-hole pair in double coupled quantum dot molecule with an ac electric field. In this quantum system, we introduce into the detuning between two dots, so this quantum system becomes an asymmetric system. With the help of Hubbard model and two-level system theory, we investigate the dynamical behaviors of this quantum system. With the help of Floquet theory, we process the numerical computation.(1) Dynamics of two elections in asymmetric double coupled quantum dots with an ac-electric field is analyzed based on the two-level systems theory., and the conditions that dynamical localization occurs is determined. Theoretical analysis show: dynamical localization still exists in such a system under the stronger electron correlation. The two electrons can be regarded as a quasi-particle, move together between two dots. The dynamics of two electrons in this quantum system are mainly confined in localization states. Which is constructed by two double-occupied states When ratio of the amplitude and frequency is the root of Bessel function, the two electrons are localized in one dot. The numerical results demonstrate the theoretical analysis reasonable.(2) We study the dynamical localization of an exciton in asymmetric double quantum dot molecule with an alternating-current field. We analyze the phenomenon of localization of an exciton in the quantum system with two-level systems theory. Theoretical analysis show: when the amplitude of the ac-field is small, the Coulomb interaction plays an important role and the electron and hole can't be divided. The dynamics of the exciton are mainly confined in a low-energy subspace. When the ratio of the amplitude and frequency is the root of Bessel function, electron and hole are localized in one dot,too. But when the amplitude of the ac-field is much lager the electron and hole can be divided. The numerical results, based on Floquet theory, demonstrate the theoretical analysis reasonable. Besides, we give the formulation of the entangled state.