Separating spin and charge transport in single wall carbon nanotubes

TL;DR

This paper demonstrates spin injection and detection in single wall carbon nanotubes using a non-local geometry that isolates spin signals from charge effects, revealing a 25% contact spin polarization.

Contribution

The study introduces a four-terminal non-local measurement method to separate spin and charge transport in carbon nanotubes, eliminating spurious effects and accurately measuring spin polarization.

Findings

Spin polarization at contacts is approximately 25%.

Non-local geometry isolates pure spin signals from charge effects.

Conventional two-terminal measurements are dominated by non-spin-related effects.

Abstract

We demonstrate spin injection and detection in single wall carbon nanotubes using a 4-terminal, non-local geometry. This measurement geometry completely separates the charge and spin circuits. Hence all spurious magnetoresistance effects are eliminated and the measured signal is due to spin accumulation only. Combining our results with a theoretical model, we deduce a spin polarization at the contacts of approximately 25 %. We show that the magnetoresistance changes measured in the conventional two-terminal geometry are dominated by effects not related to spin accumulation.