Alternative equation of motion approach applied to transport through a quantum dot

•We study non-equilibrium electron transport through a quantum dot coupled to metallic leads.•Equation of motion approach in which Green functions is differentiated over both time variables is used.•We obtain the resonance Kondo state in the particle–hole symmetric case and in the asymmetric cases.•We calculate the density of the states of quantum dot and the differential conductance as a function of bias voltage.

We study non-equilibrium electron transport through a quantum dot coupled to metallic leads. We use an alternative equation of motion approach in which we calculate the retarded Green function of the impurity by differentiating Green functions over both time variables. Such an approach allows us to obtain the resonance Kondo state in the particle–hole symmetric case and in the asymmetric cases. We apply this technique for calculating the density of the states of quantum dot and the differential conductance as a function of bias voltage. The differential conductance dependence on temperature and on Coulomb interaction is also calculated.