PAULI PRINCIPLE IN THE THEORY OF NONLINEAR ELECTRONIC TRANSPORT

In approaches to the theory of electronic transport, such as the Boltz mann equation and the Landauer-Buttiker formalism, the problem arises as to how to take into account the exclusion principle. Usually one in troduces ad hoc statistical factors to restrict the electron final sta tes to unoccupied levels. Such a procedure in general leads to incorre ct results. This is shown by a study of the friction coefficient for a localized perturbation moving in a free-electron gas. The exact expre ssion for the friction coefficient does not include a Pauli restrictio n. It is only in the case where the scattering potential has inversion symmetry or for one-dimensional systems that the Pauli term vanishes identically. Therefore, we present a detailed study using a scattering potential in two dimensions without inversion symmetry. Our numerical results show a discrepancy between the exact quantum-mechanical calcu lation and the probabilistic approach.