Nonequilibrium Fock space for the electron transport problem.

Based on the formalism of thermofield dynamics we propose a concept of nonequilibrium Fock space and nonequilibrium quasiparticles for quantum many-body system in nonequilibrium steady state. We develop a general theory as well as demonstrate the utility of the approach on the example of electron transport through the interacting region. The proposed approach is compatible with advanced quantum chemical methods of electronic structure calculations such as coupled cluster theory and configuration interaction.