Adiabatic spin pumping through a quantum dot with a single orbital level

We investigate an adiabatic spin pumping through a quantum dot with a single orbital energy level under the Zeeman effect. Electron pumping is produced by two periodic time dependent parameters, a magnetic field, and a difference of the dot-lead coupling between the left and right barriers of the dot. The maximum charge transfer per cycle is found to be e, the unit charge in the absence of a localized moment in the dot. Pumping rates for charge and spin are different, so that spin pumping is possible without charge pumping in a certain situation. They are tunable by changing the minimum and maximum value of the magnetic field.