Charge and spin pumping through a double quantum dot

TL;DR

This paper investigates adiabatic charge and spin pumping in a double quantum dot system with strong Coulomb interactions, revealing how tunneling effects and ferromagnetic contacts can generate pure spin currents and invert transport properties.

Contribution

It introduces a real-time diagrammatic approach to analyze charge and spin pumping, highlighting the role of tunneling-induced renormalization and thermally excited states in different coupling regimes.

Findings

Tunneling through thermally excited states influences charge and spin pumping.

Pure spin currents can be generated with ferromagnetic contacts.

Transport direction can invert, affecting tunneling magneto-resistance.

Abstract

We calculate adiabatic charge and spin pumping through a serial double quantum dot with strong Coulomb interaction, coupled to normal metal or ferromagnetic contacts. We use a real-time diagrammatic approach in the regime of weak coupling to the reservoirs. In the case of weak interdot tunnel coupling we investigate the influence of tunnel-induced renormalization effects due to charge fluctuations on the pumped charge and spin. We show that tunneling through thermally excited states can play an important role in the strong interdot coupling regime. In particular, for ferromagnetic contacts, both effects enable the generation of pure spin currents. Furthermore they can lead to an inverted spin-valve effect or even to the inversion of the transport direction going along with a diverging tunneling magneto-resistance.