Center for Artificial Low Dimensional Electronic Systems

Engineer spin-orbit coupling in graphene using interfacial interactions

Dong-Keun Ki

September 5(Mon) - September 5(Mon), 2016

Engineer spin-orbit coupling in graphene using interfacial interactions

Dong-Keun Ki

Department of Quantum Matter Physics and Group of Applied Physics

University of Geneva, Switzerland

Spin-orbit coupling (SOC) in graphene is of central interest for many reasons. Monolayer graphene with intrinsic SOC, for instance, is the firstly proposed topological insulator and its high-quality transport properties—such as large field-effect, high mobility, etc—are also known to be highly valuable for spintronic applications. Graphene few-layers, in addition, can offer new twists to the physics of SOC in 2D systems. SOC in graphene, however, is extremely small and the effect is almost undetectable in experiments. In this regards, here we demonstrate the possibility of engineering the SOC in graphene using interfacial interactions with semiconducting transition metal dichalcogenides (TMDs). We first show that in all devices investigated—irrespective of the device details, such as TMD materials (WS2 [1], WSe2, and MoS2) and graphene layers used, charge mobility and density, etc—a clear weak anti-localization (WAL) effect is observed at low temperatures due to the presence of the strong SOC in the system. Secondly, we find that, thanks to the weak interfacial interactions, high-quality transport properties of graphene are well preserved with the mobility reaching up to 300,000 cm2/Vs. More interestingly, the theory for monolayer graphene on TMD predicts that under certain conditions, topologically protected edge states can emerge in the system. At last, we further discuss the possibility of using bilayer graphene to tune the SOC in the system. Our study, therefore, opens a new way to explore SOC-related phenomena in graphene with diverse characteristics and to exploit them for new spintronic devices.

[1] Z. Wang, D.-K. Ki, H. Chen, H. Berger, A. H. MacDonald, A. F. Morpurgo, Nat. Commun. 6, 8339 (2015).