Theoretical Study On Electronic Transport Properties Of Coupledquantum-Dot System Connected To Three Terminals

With the development of material technology and ultra-micro fabrication technique, the semiconductor microstructure with mesoscopic dimension have come within reach. Quantum dot and quantum dots array have been fabricated in experiment successfully. These low dimensional mesoscopic systems have many novel marvelous phenomena due to their energy band to be tailored, quantum size effects and quantum interference, and thus received much current attention. Especially for coupled-quantum-dot systems, no matter the spatial symmetry, size and tunnel coupling between quantum dots are all controllable. In this way, the dream of controlling solid comes true. As the typical representative exhibiting quantum effects in mesoscopic physics, quantum dots and mesoscopic ring have become one of the most active areas. In this paper, we present in some detail theoretical investigation, using Green'functions approach, on the spectral and quantum transport properties of quantum dots coupled to three terminals and three quantum dots embedded in a Aharonov-Bohm ring.We have studied nonequilibrium quantum transport through a T-shaped four-quantum–dot system with three terminals under dc bias voltage. Both Dyson equations and equations of motion method for Green functions are used to obtain the current formula. By exploiting the Green's functions, the electron transport in a three-terminal system can be reformulated into the electron transport in an effective two-terminal system. The calculations reveal that the transmission probabilities display oscillation structures. To understand the results of the calculations for the structure, we have calculated the local densities of states. We have found that the characteristics of the transmission spectra arise from the fact that the confined states in the systems are localized in differently quantum dots and can contribute very differently to different transmission probabilities of the systems. In addition, the tunnel coupling between dots, the energy level of each dot and the coupling dot and lead play crucial roles in the transport properties of the system, especially when the single-dot Fermi levels of the four dots are aligned, with the increasing ofΓMfrom zero to some proper value, antiresonance will be transferred to resonance at the single-dot Fermi level. This...