Adiabatic charge and spin pumping through quantum dots with ferromagnetic leads

TL;DR

This paper investigates adiabatic electron and spin pumping through quantum dots with ferromagnetic leads, revealing how spin polarization and lead magnetization influence charge and spin transport.

Contribution

It introduces a real-time diagrammatic technique for analyzing adiabatic pumping in strongly interacting quantum dots with ferromagnetic contacts, highlighting new effects of lead polarization.

Findings

Spin and charge can be pumped in opposite directions depending on coupling.

Pumped charge shows angular dependence, becoming more anharmonic with higher polarization.

The method accounts for strong Coulomb interactions in the dot.

Abstract

We study adiabatic pumping of electrons through quantum dots attached to ferromagnetic leads. Hereby we make use of a real-time diagrammatic technique in the adiabatic limit that takes into account strong Coulomb interaction in the dot. We analyze the degree of spin polarization of electrons pumped from a ferromagnet through the dot to a nonmagnetic lead (N-dot-F) as well as the dependence of the pumped charge on the relative leads' magnetization orientations for a spin-valve (F-dot-F) structure. For the former case, we find that, depending on the relative coupling strength to the leads, spin and charge can, on average, be pumped in opposite directions. For the latter case, we find an angular dependence of the pumped charge, that becomes more and more anharmonic for large spin polarization in the leads.