All-Electrical Control and Temperature Dependence of the Spin and Valley Hall Effect in Monolayer WSe₂ Transistors

Heavy metal-based two-dimensional van der Waals materials have a large, coupled spin and valley Hall effect (SVHE) that has potential use in spintronics and valleytronics. Optical measurements of the SVHE have largely been performed below 30 K, and understanding of the SVHE-induced spin/valley polarizations that can be electrically generated is limited. Here, we study the SVHE in monolayer p-type tungsten diselenide (WSe₂). Kerr rotation (KR) measurements show the spatial distribution of the SVHE at different temperatures, its persistence up to 160 K, and that it can be electrically modulated via gate and drain bias. A spin/valley drift and diffusion model together with a reflection measurement and a four-port electrical measurement is used to interpret the KR data. A lower-bound spin/valley lifetime is predicted to be of 40 ns and a mean free path of 240 nm below 90 K, 2 orders of magnitude higher than a previous work that uses similar methods. The spin/valley polarization on the edge is calculated to be ∼4% at 45 K. These results are important steps toward practical use of the SVHE.