Nonequilibrium diagrammatic technique for Hubbard Green functions

Utilizing many-body states of the isolated molecule, Hubbard nonequilibrium Green function (NEGF) is able to account for the intra-system interactions exactly while coupling to the contacts is treated perturbatively. We introduce nonequilibrium diagrammatic technique for the Hubbard NEGF, which allows building controlled approximations for both Green (two-time) and multi-time correlation functions. The formulation is an extension of equilibrium considerations for strongly correlated lattice models to nonequilibirum realm of current carrying molecular junctions. We demonstrate viability of the approach with numerical simulations for a generic junction model of quantum dot coupled to two electron reservoirs.