Theory of a Magnetically-Controlled Quantum-Dot Spin Transistor

TL;DR

This paper presents a theoretical study of a quantum-dot spin transistor controlled by magnetic interactions, demonstrating how spin accumulation and precession influence conductance and enable magnetic transistor operation.

Contribution

It introduces a model for a quantum-dot spin transistor influenced by ferromagnetic leads and analyzes the effects of spin-flip and precession processes on transport.

Findings

Spin accumulation causes magnetoresistance in the device.

Both incoherent spin-flip and coherent precession significantly affect current.

Magnetic control enables transistor-like operation without charge current in the base.

Abstract

We examine transport through a quantum dot coupled to three ferromagnetic leads in the regime of weak tunnel coupling. A finite source-drain voltage generates a nonequilibrium spin on the otherwise non-magnetic quantum dot. This spin accumulation leads to magnetoresistance. A ferromagnetic but current-free base electrode influences the quantum-dot spin via incoherent spin-flip processes and coherent spin precession. As the dot spin determines the conductance of the device, this allows for a purely magnetic transistor-like operation. We analyze the effect of both types of processes on the electric current in different geometries.