Graphene-WS2 heterostructures for tunable spin injection and spin transport

We report the first measurements of spin injection into graphene through a 20-nm-thick tungsten disulphide (WS2) layer, along with a modified spin relaxation time (tau(s)) in graphene in the WS2 environment, via spin-valve and Hanle spin-precession measurements, respectively. First, during the spin injection into graphene through a WS2-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 WS2 crystal, and observe a significant reduction in the tau(s) down to 17 ps in graphene in the WS2 covered region, compared to that in its pristine state. The reduced tau(s) indicates the WS2-proximity induced additional dephasing of the spins in graphene.