Spin current through a quantum dot in the presence of an oscillating magnetic field

Nonequilibrium spin transport through an interacting quantum dot is analyzed. The coherent spin oscillations in the dot provide a generating source for spin current. In the interacting regime, the Kondo effect is influenced in a significant way by the presence of the processing magnetic field. In particular, when the precession frequency is tuned to resonance between spin-up and spin-down states of the dot, Kondo singularity for each spin splits into a superposition of two resonance peaks. The Kondo-type cotunneling contribution is manifested by a large enhancement of the pumped spin current in the strong coupling low temperature regime.