One can partition the layered structure into left contact with index , device with index , and right contact with index (Fig. G.1). The device corresponds to the region where one solves the transport equations and the contacts are the highly conducting regions connected to the device.
While the device region consists of only layers, the matrices corresponding to the GREEN's functions (4.11) and (4.12) are infinite dimensional due to the semi-infinite contacts. It is shown next, that the influence of the semi-infinite contacts can be folded into the device region, where the semi-infinite contacts only affect layers and of the device region.
As shown next, the influence of the semi-infinite contacts can be folded into
the device region by adding a self-energy to the device region. This can be
viewed as an additional self-energy, due to the transitions between the device
and the contacts.