Coupled Quantum Dot In The Transport Properties Of Theoretical Research

In this thesis,we study the time-dependent transport properties in coupled quantum dot system under the influence of ac electric field.Using Floquet theory,we investigate dynamical localization effect on transport properties of an ac driving coupled quantum dot array,find photon-assistant Fano resonance in serially coupled triple quantum dots,and reveal competition between dynamical localization and Fano resonance in symmetric A-type coupled triple quantum dots.In chapter one,we introduce the main characteristics of quantum dot system and summarize the current development in the field of time-dependent transport of coupled quantum dots.In chapter two,we study dynamical localization effect on transport properties of an ac driving coupled quantum dot array.We find that if the ratio of the field magnitude to frequency is a root of the zeroth order Bessel function, a minimum of the average current appears making a signal to dynamical localization of one initially localized electron and collapse of the quasi-energy spectrum of the system.The dynamical localization effect is strengthened as a result of the increase of the quantum dot number,and is weakened on account of the increase of the dots-lead hopping rate.In chapter three,we study photon-assistant Fano resonance in serially coupled triple quantum dots based on calculations of the electronic structure of the system.It is found that the A-type energy level of the system has great impact on the transport properties.For an asymmetric configuration,there is a symmetric peak in current-AC frequency curve due to resonant photon induced mixing between left dot and middle dot.In the symmetric configuration, an asymmetric Fano line shape appears in the current-frequency curve with the help of "trapping dark state".In chapter four,we study the control between dynamical localization and Fano resonance in symmetric A-type coupled triple quantum dots.Under appropriate condition,dynamical localization(DL) and Fano resonance (FR) could both appear due to quantum interference effects.There is drastic competition between DL and FR as a consequence of competition between super-exchange and coherent destruction of tunneling.The phenomena represent two different ways of electron trapping,thus we can control the behavior of electrons under suitable condition,that provides a convenient way to fabricate the quantum switch.