Spin-polarized parametric pumping: Theory and numerical results

Abstract

We have extended the previous parametric electron pumping theory to include the spin-polarized pumping effect. Specifically, we consider a parametric pump consisting of a nonmagnetic system with two ferromagnetic leads whose magnetic moments orient at an angle $\ensuremath{\theta}$ with respect to each other. In our theory, the leads can be maintained at different chemical potentials. As a result, the current is driven due to both the external bias and the pumping potentials. When both $\ensuremath{\theta}$ and the external bias are zero, our theory recovers the known theory. In particular, two cases are considered: (i) in the adiabatic regime, we have derived the pumped current for an arbitrary pumping amplitude and external bias and (ii) at finite frequency, the system is away from equilibrium, and we have derived the pumped current up to quadratic order in pumping amplitude. From our numerical results we found that the pumped current can be modulated by the angle $\ensuremath{\theta},$ showing interesting spin-valve effects.