2002 Volume 71 Issue 12 Pages 2969-2974
We study the high- and low-voltage properties of the out-of-equilibrium Anderson model for quantum dots, using a functional method in the Keldysh formalism. The Green's function at the impurity site can be regarded as a functional of a nonequilibrium distribution function feff(ω). The dependence of the Green's function on the bias voltage V and temperature T arises through feff(ω). From this behavior as a functional, it is shown that the nonequilibrium Green's function at eV→∞ is identical to the equilibrium one at T→∞. This correspondence holds when the couplings of the dot and two leads, at the left and right, are equal. In the opposite limit, for small eV, the low-energy behavior of the Green's function can be described by the local Fermi-liquid theory up to terms of order (eV)2. These results imply that the correlation effects due to the Coulomb interaction U can be treated adiabatically in the two limits, at high and low bias voltages.
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