Graphene Spin Transistor

TL;DR

This paper demonstrates spin transport in graphene using non-local four-probe experiments, revealing quantum-coherent behavior, spin current detection at room temperature, and gate-tunable spin signals, advancing graphene spintronics research.

Contribution

First experimental demonstration of spin current detection in graphene via non-local measurements with ferromagnetic contacts, showing quantum-coherent transport and room-temperature operation.

Findings

Sharp switching and sign-reversal of non-local resistance at coercive field

Gate-dependent oscillations indicating quantum coherence

Spin signals observed up to 300 K

Abstract

Graphitic nanostructures, e.g. carbon nanotubes (CNT) and graphene, have been proposed as ideal materials for spin conduction[1-7]; they have long electronic mean free paths[8] and small spin-orbit coupling[9], hence are expected to have very long spin-scattering times. In addition, spin injection and detection in graphene opens new opportunities to study exotic electronic states such as the quantum Hall[10,11] and quantum spin Hall[9] states, and spin-polarized edge states[12] in graphene ribbons. Here we perform the first non-local four-probe experiments[13] on graphene contacted by ferromagnetic Permalloy electrodes. We observe sharp switching and often sign-reversal of the non-local resistance at the coercive field of the electrodes, indicating definitively the presence of a spin current between injector and detector. The non-local resistance changes magnitude and sign quasi-periodically with back-gate voltage, and Fabry-Perot-like oscillations[6,14,15] are observed, consistent with quantum-coherent transport. The non-local resistance signal can be observed up to at least T = 300 K.