Theoretical Study of Nonequilibrium Electron Transport and Charge Distribution in a Three-Site Quantum Wire

Abstract

We derive the nonequilibrium transport property formulas for a three-site quantum wire model using Keldysh formalism. Some rigorous formulas in the case of noninteraction are provided for direct calculations. On the basis of the numerical calculations, we investigate the differential and total conductances, transport current, and on-site electronic charges of a wire in some special cases. For a uniform-ingredient wire, if the temperature T=0 K, it shows that, when site–site couplings in the wire are stronger than wire–electrode couplings, resonant tunneling transport takes place and the phenomenon of conductance quantization can be easily observed. In the opposite case, these quantum effects on transport disappear gradually with the increase in the strength of wire–electrode couplings. We also discuss the charge distributions in the three sites of the wire and the characteristics of the charge barrier (Schottky barrier) regardless of Coulomb interaction. If T>0 K, all the line shapes of the transport properties become smoother than those at T=0 K owing to thermal fluctuations. For a wire containing impurities, the line shapes of the transport properties change because of the change of system electronic states.