Single-impurity Anderson model out of equilibrium

Transport through a localized site connected to two leads with different chemical potentials---the Anderson model out of equilibrium---is investigated via time-loop perturbation theory. The differential conductance is obtained from an analytic expression for the site density of states, including a magnetic field. In addition to the usual Kondo peaks in the density of states which are shifted by the Zeeman energy from the chemical potentials, an additional peak is found to survive at one chemical potential for each spin if the bias exceeds the Zeeman splitting. {} 1996 The American Physical Society.