Opto-Valleytronic Spin Injection in Monolayer MoS2/Few-Layer Graphene Hybrid Spin Valves

TL;DR

This paper demonstrates the first opto-valleytronic spin injection and lateral spin transport at room temperature in a monolayer MoS2/few-layer graphene hybrid device, combining optical and electrical control of spin in 2D materials.

Contribution

It introduces a novel hybrid spin valve device enabling optical spin injection and transport in 2D materials at room temperature, advancing spintronics and valleytronics integration.

Findings

Optical spin injection is achieved across a TMD/graphene interface.

Spin polarization magnitude and direction are controlled by photon helicity and energy.

Room temperature spin transport is confirmed via Hanle measurements.

Abstract

Two dimensional (2D) materials provide a unique platform for spintronics and valleytronics due to the ability to combine vastly different functionalities into one vertically-stacked heterostructure, where the strengths of each of the constituent materials can compensate for the weaknesses of the others. Graphene has been demonstrated to be an exceptional material for spin transport at room temperature, however it lacks a coupling of the spin and optical degrees of freedom. In contrast, spin/valley polarization can be efficiently generated in monolayer transition metal dichalcogenides (TMD) such as MoS2 via absorption of circularly-polarized photons, but lateral spin or valley transport has not been realized at room temperature. In this letter, we fabricate monolayer MoS2/few-layer graphene hybrid spin valves and demonstrate, for the first time, the opto-valleytronic spin injection across a TMD/graphene interface. We observe that the magnitude and direction of spin polarization is controlled by both helicity and photon energy. In addition, Hanle spin precession measurements confirm optical spin injection, spin transport, and electrical detection up to room temperature. Finally, analysis by a one-dimensional drift-diffusion model quantifies the optically injected spin current and the spin transport parameters. Our results demonstrate a 2D spintronic/valleytronic system that achieves optical spin injection and lateral spin transport at room temperature in a single device, which paves the way for multifunctional 2D spintronic devices for memory and logic applications.