Replacing Leads By Self-Energies Using Non-Equilibrium Green\u27S Functions

Open quantum systems consist of semi-infinite leads which transport electrons to and from the device of interest. We show here that within the non-equilibrium Green\u27s function technique for continuum systems, the leads can be replaced by simple c-number self-energies. Our starting point is an approach for continuum systems developed by Feuchtwang. The reformulation developed here is simpler to understand and carry out than the somewhat unwieldly manipulations typical in the Feuchtwang method. The self-energies turn out to have a limited variability: the retarded self-energy Σr depends on the arbitrary choice of internal boundary conditions, but the non-equilibrium self-energy or scattering function Σ\u3c which determines transport is invariant for a broad class of boundary conditions. Expressed in terms of these self-energies, continuum non-equilibrium transport calculations take a particularly simple form similar to that developed for discrete systems. © 2003 Elsevier B.V. All rights reserved