Proximity-Induced Spin Hall Effect in Graphene/WSe2 van der Waals Heterostructures with Tunable, Highly Efficient Spin-to-Charge Conversion

Abstract

The proximity effect in two-dimensional materials opens ways to achieve important functions for future spintronic devices. In van der Waals heterostructures (vdWHs), transition metal dichalcogenides (TMD) can be used to enhance the spin-orbit coupling of graphene leading to highly efficient spin-to-charge conversion (SCC) by spin Hall effect (SHE) that is predicted to be controllable by a gate voltage. Here, we report for the first time the observation of the SHE in graphene proximitized with WSe2 in a vdWHs. These kind of vdWHs are a promising platform to study a variety of spin-dependent phenomena [1,2]. By Hanle precession measurements, we quantify the spin transport and SCC parameters from 10 K up to room temperature. Exceptional for graphene/TMD devices, the sole mechanism is the SHE for all measurements and no Rashba-Edelstein effect is observable. Importantly, we are able to amplify and turn off the SCC by applying a back-gate voltage, demonstrating the long-awaited milestone of an electrically-tunable SHE. The amplified SCC shows a high efficiency, measured with an unprecedented SCC length of larger than 20 nm, defined as the product of the spin Hall angle (ΘSH) and the spin diffusion length (λs). These results show the capability of two-dimensional materials to advance towards the implementation of novel spin-based devices and future applications.