Theory of spin pumping through an interacting quantum dot tunnel coupled to a ferromagnet with time-dependent magnetization

TL;DR

This paper explores adiabatic spin pumping through an interacting quantum dot coupled to a ferromagnet with time-varying magnetization, introducing new schemes for generating charge and pure spin currents.

Contribution

It extends a diagrammatic real-time technique to handle time-dependent lead properties and proposes two schemes for spin pumping using amplitude variation and magnetization rotation.

Findings

Amplitude variation combined with level tuning produces charge and spin currents.

Magnetization rotation can generate pure spin currents without charge flow.

Interaction-induced exchange field influences pumping efficiency.

Abstract

We investigate two schemes for pumping spin adiabatically from a ferromagnet through an interacting quantum dot into a normal lead, which exploit the possibility to vary in time the ferromagnet's magnetization, either its amplitude or its direction. For this purpose, we extend a diagrammatic real-time technique for pumping to situations in which the leads' properties are time dependent. In the first scheme, the time-dependent magnetization amplitude is combined with a time-dependent level position of the quantum dot to establish both a charge and a spin current. The second scheme uses a uniform rotation of the ferromagnet's magnetization direction to generate a pure spin current without a charge current. We discuss the influence of an interaction-induced exchange field on the pumping characteristics.