A Double Quantum Dot Spin Valve

TL;DR

This paper demonstrates a double quantum dot spin valve in InAs nanowires with ferromagnetic split-gates, achieving electrically tunable spin polarization and magnetoresistance, advancing nanoscale spintronic device capabilities.

Contribution

It introduces a novel double quantum dot spin valve with independent ferromagnetic gates, enabling electrical control of spin polarization and magnetoresistance at the nanoscale.

Findings

Achieved a single QD polarization of ~27%.

Demonstrated TMR tunable between +80% and -90%.

Model accurately predicts gate-tunable QD polarization.

Abstract

A most fundamental and longstanding goal in spintronics is to electrically tune highly efficient spin injectors and detectors, preferably compatible with nanoscale electronics. Here, we demonstrate all these points using semiconductor quantum dots (QDs), individually spin-polarized by ferromagnetic split-gates (FSGs). As a proof of principle, we fabricated a double QD spin valve consisting of two weakly coupled semiconducting QDs in an InAs nanowire (NW), each with independent FSGs that can be magnetized in parallel or anti-parallel. In tunneling magnetoresistance (TMR) experiments at zero external magnetic field, we find a strongly reduced spin valve conductance for the two anti-parallel configurations, with a single QD polarization of $\sim 27\%$. The TMR can be significantly improved by a small external field and optimized gate voltages, which results in a continuously electrically tunable TMR between $+80\%$ and $-90\%$. A simple model quantitatively reproduces all our findings, suggesting a gate tunable QD polarization of $\pm 80\%$. Such versatile spin-polarized QDs are suitable for various applications, for example in spin projection and correlation experiments in a large variety of nanoelectronics experiments.