Influence of the Coulomb interaction on the spin-polarized current in the quantum dot system in the presence of the bias voltage pulse

We consider the influence of the intra-dot Coulomb interaction U on the electron transport through the quantum dot coupled with non-magnetic leads. The transient spin-dependent current generated by a pulsed bias voltage applied across the quantum dot system is calculated using the equation of motion method for appropriate correlation functions. We find that the coherent quantum beats in both total current and spin current observed for vanishing U are strongly suppressed by non-zero interaction in the case of a single step-like voltage pulse applied to the system. It is found that for a pulsed bias voltage the Coulomb interaction can lead to much stronger spin polarized current occurring in some time windows. The possibility of the pure spin current together with the vanishing charge current is also discussed for the quantum dot coupled with three leads. (c) 2013 Elsevier B.V. All rights reserved.