Strong Spin-Orbit Interaction in ultra clean graphene/ transition-metal dichalcogenide heterostructures

Van der Waals heterostructures based on stacking two dimensional materials gives rise to new possibilities for designing tunable electronic systems. While combining the merits of individual layers, heterostructures provide a platform for studying interfacial interactions [1]. Among the many phenomena achieved by this proximity effect, inducing spin-orbit coupling (SOC) in graphene has attracted much attention for potential applications in topological physics. We study the enhancement of SOC in graphene induced by transition-metal dichalcogenides (TMDs). High carrier mobility at low temperature suggests that our devices have high quality graphene and very clean graphene/TMD interfaces. We measure magnetoresistance in these devices, which is large and positive, indicating the presence of ultra-strong weak antilocalization (WAL), as a signature of SOC induced in graphene. In contrast to previous works [2-3], our WAL strength is much higher, and we have explored the variation with carrier density more systematically. The WAL feature gradually decreases with increasing temperature and becomes unobservable above 60K.

[1] Geim, Andre K., et al. Nature 499.7459 (2013): 419.
[2] Wang, Zhe, et al. Nature communications 6 (2015): 8339.
[3] Yang, Bowen, et al. 2D Materials 3.3 (2016): 031012.