Fèlix Casanova: Manipulating spin currents with graphene-based heterostructures

The integration of the spin in charge-based electronic devices has revolutionized both sensing and memory capability in microelectronics. Further development in spintronic devices requires electrical manipulation of spin current as well as spin-charge interconversion for logic operations. Graphene has raised as an outstanding spin transporter due to its weak spin-orbit coupling (SOC) [1]. However, a strong SOC is required for an electrical control of the spin state, as in the seminal proposal of Datta and Das [2], or to achieve spin-charge interconversion, via the spin Hall effect. In this talk, I will show how SOC can be induced in graphene by proximity with another material, allowing us to manipulate spin currents. A very simple approach by combining Pt with a graphene channel already shows a very large spin-to-charge voltage output at room temperature [3], opening up exciting opportunities for spin-orbit logic circuits. A radically different approach is by engineering a van der Waals (vdW) heterostructure which combines graphene with MoS 2 , a transition metal dichalcogenide with strong SOC and semiconducting properties. The spin transport in the graphene channel is modulated between ON and OFF states by tuning the spin absorption into the MoS 2 layer with a gate electrode [4]. Our demonstration of a spin field-effect switch using 2D materials identifies a new route towards spin logic operations for beyond CMOS technology. Furthermore, the vdW heterostructure at the core of our experiment allows us to unambiguously demonstrate experimentally [5] a predicted spin Hall effect in graphene due to spin-orbit proximity with the MoS 2 [6]. The combination of long-distance spin transport and spin Hall effect in different parts of the same material gives rise to an unprecedented spin-to-charge conversion efficiency, opening exciting opportunities in a variety of future spintronic applications [5].

[1] J. Ingla-Aynes et al., Nano Lett. 16, 4825 (2016).

[2] S. Datta and B. Das, Appl. Phys. Lett. 56, 665 (1990).

[3] W. Yan et al., Nat. Commun. 8, 661 (2017).

[4] W. Yan et al., Nat. Commun. 7, 13372 (2016).

[5] C. K. Safeer at al. arXiv:1810.12481

[6] J. H. Garcia et al., Nano Lett. 17, 5078 (2017).