Full Counting Statistics In Two-level Quantum Dot With Exchange Coupling

The quantum transport in the mesoscopic systems has attracted much attention in the theoretical and experimental research. In particular, the investigate on the shot noise in quantum transport is useful for revealing the internal level structure, the information of the charge transfer and the properties of many-body entanglement, and so on. In this thesis, firstly, the study on the quantum dot is introduced, including the preparation, the properties, the applications and the shot noise of the quantum dot. Secondly, we introduce the quantum master equation and the particle-number-resolved quantum master equation method of mesoscopic transport in detail based on Liouville equation, and expound the basic thought of the full count statistics theory as well as its application in mesoscopic transport. Finally, we study the electronic transport characteristics of a two-level quantum dot with exchange coupling based on the particle-number-resolved quantum master equation and the full count statistics theory. We give the influence of spin exchange coupling, coulomb repulsion and asymmetric coupling quantum dots on average current, shot noise and skewness of the two-level quantum dot. The results show exchange coupling and coulomb interaction do not influence the single electronic state channel, only affect to two electronic spin single state and spin triple state channel, Increasing exchange coupling just corrects the distribution of the channel level and changes the range of the super-Poissonian noise. But that do not change the maximum and minimum value of shot noise. And the coulomb interaction not only translates the platform of shot noise, but also leads to a large super-Poissonian noise value for the stronger asymmetry coupling and the large coulomb interaction. The super-Poissonian noise occurs more easily for the large spin polarization and asymmetry coupling to the leads. It is interesting that spin single state and spin triple state have different affect to the shot noise. The shot noise decreases greatly when two spin-singlet channel levels participate simultaneously in the transport, whereas two spin-triplet channel levels participate simultaneously in the transport it increases markedly.