Nonequilibrium Kondo effect in quantum dots

The nonequilibrium Kondo effect in a quantum dot coupled to metallic leads is analyzed theoretically. Electron interaction on the dot is taken into account in terms of the Hubbard model for an arbitrary value of the correlation parameter U. The nonequilibrium Green function technique is used to calculate electric current and density of states. The key point of the approach is the consistency of the approximations used to calculate the lesser and retarded (advanced) Green functions. The Green functions are calculated on equal footing, i.e., within the same approximation in the framework of the equation of motion method.