Influence Of Impurities On The Quantum Dot System Fano Effect And The Thermoelectric Effect

In recent years, the low dimensional nanostructure thermoelectric materials become a newstarting point for the study of thermoelectric materials. Both experimental and theoretical researchs have proved that the low dimensional thermoelectric materials can greatly improve the thermoelectric properties of the materials. Transforming the heat energy into the electrical energy is called the thermoelectric effect phenomenon, of which the most important is the thermoelectricity phenomena. Because the metal material thermoelectromotive force is very small, only serves as the survey temperature the thermocouple. After the semiconducting material appears, bigger the thermoelectromotive force may be obtained in the semiconduct material, therefore, the semiconducting material possesses the higher thermoelectric conversion efficiency.Thermoelectric figure of merit Z characterize the quality factor of the thermoelectric materials. Evaluating the thermoelectric conversion efficiency of the thermoelectric material can be measured by thermoelectric figure of merit Z, bigger value corresponding to the thermoelectric conversion efficiency higher device. The relationship of electrical conductivity G, Seebeck coefficient S and thermal conductivity coefficient K is a key to determine the thermoelectric figure of merit. The three parameters interdependenced each other, all related to electronic structure, the current carrier scattering and the transport properties of the material. In the classical theory category three parameters obey the Mott rule and the Widemann- Franz law. It is difficult to adjust simultaneously the three parameters to obtain high thermoelectric optimal value, but for the low dimensional nanostructured materials, the two laws are no longer applicable. In recent years, the theoretical and experimental researchs show that reducing the dimensions of the material to improve the performance of thermoelectric materials is more effectively.Quantum dots possess the low dimensional structure exhibit obviously as the quantum effect, contains the rich quantum transmission attribute. Contributing to the thermal conductivity by the density of electronic states and phonon quantum dots made improving the thermoelectric figure of merit is possible. Predictably, the connection point of quantum dot devices is the best candidate to explore the thermoelectric properties of low dimensional structures; the quantum interference transport phenomenons induced by quantum energy levels, Fano effect, Coulomb oscillation in quantum dot quantum can arose the novel phenomenon of thermoelectrice characteristices. Parallel coupled quantum dot AB interferometer is a kind of typical low dimensional structure, possessing abundant adjustable parameters. By adjusting the local magnetic flux and gate voltage can bring the rich quantum transport characteristics in the system.This thesis uses the non-equilibrium Green function theory investigating Fano effect and the thermoelectric properties of the parallel coupled quantum dot AB interference with impurity coupled into in the three different ways, with influenced by the magnetic field and the gate voltage. This paper focus on discuss the influence of Fano effect and thermoelectric effect caused by localized impurity existing in the system. This article performs theoretically numerical simulation and the numerical analysis to the linear conductance, the thermal power and the thermoelectricity figure of merit, the results show that Fano interference determined the thermoelectric effect in the system. The thermoelectric effect only occurs in the range of the conductance spectrum of Fano interference. Fano interference effect is more obvious, the greater the value of the merit is. The most significant Fano effect and the thermoelectric effect appears when impurities coupled with the local state, but it is extreme small when impuritise is coupled with the electrode endpoint. Therefore, we expect that these results can help us to adjust the influence of impurities on the thermoelectric effect in parallel coupled quantum dot AB interference.