Numerical analyses of the nonequilibrium electron transport through the Kondo impurity beside the Toulouse point

Nonequilibrium electron transport through the Kondo impurity is investigated numerically for the system with 20 conduction-electron levels. The electron current under finite voltage drop is calculated in terms of the 'conductance viewed as transmission' picture proposed by Landauer. Here, we take into account the full transmission processes of both the many-body correlation and the hybridization amplitude up to infinite order. Our results demonstrate, for instance, how the exact solution of the differential conductance by Schiller and Hershfield obtained at the Toulouse point becomes deformed by more realistic interactions. The differential-conductance-peak height is suppressed below e²/h with the width hardly changed through reducing the Kondo coupling from the Toulouse point, whereas it is kept unchanged by further increase of the coupling. We calculated the nonequilibrium local Green function as well. This clarifies the spectral property of the Kondo impurity driven far from equilibrium.