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

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.

Nano Letters, in press

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• Optical spectroscopy of excited exciton states in MoS2 monolayers in van der Waals heterostructures
• Optospintronics in graphene via proximity coupling
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• Proximity spin-orbit and exchange coupling in ABA and ABC trilayer graphene van der Waals heterostructures
• Symmetry and Control of Spin-Scattering Processes in Two-Dimensional Transition Metal Dichalcogenides
• Experimental observation of spin-split energy dispersion in high-mobility single-layer graphene/WSe2 heterostructures
• Deterministic direct growth of WS2 on CVD graphene arrays
• Signatures of electric field and layer separation effects on the spin-valley physics of MoSe${}_2$/WSe${}_2$ heterobilayers: from energy bands to dipolar excitons
• Optical detection of long electron spin transport lengths in a monolayer semiconductor
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• Proximity-enhanced valley Zeeman splitting at the WS${}_2$/graphene interface
• Fermi Level Depinning in Two-Dimensional Materials Using a Fluorinated Bilayer Graphene Barrier
• Landau Levels of Bilayer Graphene in a WSe${}_2$/Bilayer Graphene van der Waals Heterostructure
• Electric field controlled valley-polarized photocurrent switch based on the circular bulk photovoltaic effect
• Theory of spin-charge-coupled transport in proximitized graphene: An SO(5) algebraic approach
• Magnetic field control of light-induced spin accumulation in monolayer MoSe${}_2$
• Single- and narrow-line photoluminescence in a boron nitride-supported MoSe${}_2$/graphene heterostructure
• Valley-dependent transport through graphene quantum dots due to proximity-induced, staggered spin-orbit couplings
• Interface Magnetism in Vanadium-doped MoS${}_2$/Graphene Heterostructures
• Resistively detected electron spin resonance and g-factor in few-layer exfoliated MoS2 devices
• Ultrafast Spin Injection in Graphene via Dynamical Carrier Filtering at Transition Metal Dichalcogenide Interfaces