Optospintronics in graphene via proximity coupling

TL;DR

This paper demonstrates a novel optospintronics approach in graphene by creating interfaces with WSe2 monolayers, enabling optical spin injection and long-distance spin transport for potential spintronic applications.

Contribution

It introduces a method to optically inject spins into graphene via proximity coupling with WSe2, overcoming low spin orbit coupling and absorption issues.

Findings

Spin polarized carriers diffuse over 3.5 micrometers in graphene.

Circularly polarized light activates spin polarization in WSe2.

Electrical detection confirms spin transport in graphene.

Abstract

The observation of micron size spin relaxation makes graphene a promising material for applications in spintronics requiring long distance spin communication. However, spin dependent scatterings at the contact/graphene interfaces affect the spin injection efficiencies and hence prevent the material from achieving its full potential. While this major issue could be eliminated by nondestructive direct optical spin injection schemes, graphenes intrinsically low spin orbit coupling strength and optical absorption place an obstacle in their realization. We overcome this challenge by creating sharp artificial interfaces between graphene and WSe2 monolayers. Application of a circularly polarized light activates the spin polarized charge carriers in the WSe2 layer due to its spin coupled valley selective absorption. These carriers diffuse into the superjacent graphene layer, transport over a 3.5 um distance, and are finally detected electrically using BN/Co contacts in a non local geometry. Polarization dependent measurements confirm the spin origin of the non local signal.