Graphene-WS$_2$ heterostructures for tunable spin injection and spin transport

TL;DR

This study demonstrates tunable spin injection into graphene through a WS$_2$ layer and observes a significant reduction in spin relaxation time due to WS$_2$-induced dephasing, advancing understanding of 2D heterostructure spin transport.

Contribution

First measurement of spin injection into graphene via a WS$_2$ layer and analysis of how WS$_2$ affects spin relaxation times in graphene.

Findings

Spin injection efficiency can be tuned by interface resistance.

Charge transport across the interface is dominated by temperature-assisted tunneling.

Spin relaxation time in graphene decreases to 17 ps under WS$_2$ influence.

Abstract

We report the first measurements of spin injection in to graphene through a 20 nm thick tungsten disulphide (WS$_2$) layer, along with a modified spin relaxation time ({\tau}s) in graphene in the WS$_2$ environment, via spin-valve and Hanle spin-precession measurements, respectively. First, during the spin-injection into graphene through a WS$_2$-graphene interface, we can tune the interface resistance at different current bias and modify the spin injection efficiency, in a correlation with the conductivity-mismatch theory. Temperature assisted tunneling is identified as a dominant mechanism for the charge transport across the interface. Second, we measure the spin transport in graphene, underneath the WS$_2$ crystal and observe a significant reduction in the {\tau}s down to 17 ps in graphene in the WS$_2$ covered region, compared to that in its pristine state. The reduced {\tau}s indicates the WS$_2$-proximity induced additional dephasing of the spins in graphene.