  By considering a correlated two-electron transport process (TET) and using a
diagrammatic analysis within the Keldysh nonequilibrium Green's function
formalism, we discuss a novel charge pump by which carriers are pumped from a
contact with low chemical potential to another contact with a higher potential.
The TET process involves two correlated incident electrons scattering and
exchanging energy with each other. The process can significantly affect charge
current density and it involves high empty states and/or low filled states of
the Fermi liquid of the leads.
