Pumping spin and charge currents from applying a time-variant field and a magnetic field to a quantum dot

Photon-electron pumping effects on a quantum dot connected to two magnetic leads in the presence of both via-dot and over-dot tunneling channels have been investigated by the evolution operator approach. It is found that a time-variant field applied to the quantum dot may give rise to charge and spin pumping at zero bias voltage for asymmetric magnetic junctions. When the magnetic field switch on, the spin-up and spin-down current can be considerably separated, then the highly spin polarized current is also generated.