Electrical Control of Valley-Zeeman Spin-Orbit-Coupling–Induced Spin Precession at Room Temperature

TLDR

Spintronics seeks electrically controlled coherent spin manipulation at room temperature, yet coherent precession has only been observed in ballistic, low‑temperature regimes, while 2D materials’ spin anisotropy and valley character offer new control knobs. The study aims to achieve coherent spin precession in bilayer graphene without an external magnetic field by manipulating anisotropic spin‑orbit coupling through proximity to WSe$_2$. This is realized by using the WSe$_2$ proximity effect to tune the anisotropic spin‑orbit coupling in bilayer graphene, enabling coherent precession in the diffusive regime. The precessing spin polarization sign is tunable via back‑gate voltage and drift current, enabling a room‑temperature spin field‑effect transistor that paves the way for energy‑efficient spin‑based logic.

Abstract

The ultimate goal of spintronics is achieving electrically controlled coherent manipulation of the electron spin at room temperature to enable devices such as spin field-effect transistors. With conventional materials, coherent spin precession has been observed in the ballistic regime and at low temperatures only. However, the strong spin anisotropy and the valley character of the electronic states in 2D materials provide unique control knobs to manipulate spin precession. Here, by manipulating the anisotropic spin-orbit coupling in bilayer graphene by the proximity effect to WSe$_2$, we achieve coherent spin precession in the absence of an external magnetic field, even in the diffusive regime. Remarkably, the sign of the precessing spin polarization can be tuned by a back gate voltage and by a drift current. Our realization of a spin field-effect transistor at room temperature is a cornerstone for the implementation of energy-efficient spin-based logic.