Gate-Tunable Spin-Charge Conversion and the Role of Spin-Orbit Interaction in Graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Graphene's weak spin-orbit interaction suggests long spin diffusion lengths, ideal for spintronics.
• Graphene was previously overlooked for spin-charge conversion due to its weak spin-orbit coupling.
• Spin-charge conversion is crucial for developing spintronic devices like spin field-effect transistors.

Purpose of the Study:

• To investigate and demonstrate electric gate tunability of spin-charge conversion in single-layer graphene.
• To identify the dominant spin-charge conversion mechanism in graphene.
• To resolve the long-standing debate regarding intrinsic versus Rashba spin-orbit interaction dominance in graphene.

Main Methods:

• Utilized spin pumping from yttrium iron garnet (YIG) to inject spin currents.
• Employed an ionic liquid top gate for electric field tuning of the graphene channel.
• Measured the resulting electromotive force (EMF) to quantify spin-charge conversion.

Main Results:

• Demonstrated electric gate control over the spin-charge conversion voltage signal in single-layer graphene.
• Identified the inverse spin Hall effect (ISHE) as the primary spin-charge conversion mechanism.
• Showcased the dominance of intrinsic spin-orbit interaction over Rashba spin-orbit interaction through gate-dependent EMF measurements.

Conclusions:

• Single-layer graphene is a viable material for efficient spin-charge conversion.
• Electric gating provides a powerful method to tune spintronic properties in graphene.
• The findings clarify the nature of spin-orbit interactions in graphene, impacting future device design.