Graphene-WS_2 heterostructures for tunable spin injection and spin transport

摘要

We report the first measurements of spin injection into graphene through a 20-nm-thick tungsten disulphide (WS_2) layer, along with a modified spin relaxation time (τ_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 τ_s down to 17 ps in graphene in the WS_2 covered region, compared to that in its pristine state. The reduced τ_s indicates the WS_2-proximity induced additional dephasing of the spins in graphene.