Microscopic Modelling of Quantum Open Systems: A Generalized Wigner-Function Approach

A microscopic approach for the simulation of quantum-transport phenomena in systems with open boundaries is proposed. We show that the application of the conventional Wigner-function formalism to this problem leads to unphysical results, like injection of coherent electronic states from the contacts. To overcome such basic limitation, we propose a generalization of the standard Wigner-function formulation, able to properly describe the incoherent nature of carrier injection at the device spatial boundaries. The latter constitutes a quantum mechanical derivation of the phenomenological injection model commonly employed in the simulation of open quantum devices.