Charge on the quantum dot in the presence of tunneling current

The calculation of the charge present in central region of the double barri er structure at nonequilibrium conditions is discussed. We propose here a s imple method to calculate nonequilibrium Green's functions which allows con sistent calculations of retarded and distribution functions. To illustrate the approach, we calculate the charge on the quantum dot coupled via tunnel barriers to two external leads having different chemical potentials mu(L) and mu(R). The obtained results have been compared with other approaches ex isting in the literature. They all agree in the equilibrium situation and t he departures grow with increasing the difference mu(L) - mu(R). (C) 2000 P ublished by Elsevier Science Ltd. All rights reserved.