Determining spin-orbit coupling in graphene by quasiparticle interference imaging.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Controlling spin-orbit coupling (SOC) in graphene is essential for topological states and spintronic devices.
• Graphene-on-transition metal dichalcogenide heterostructures are promising for inducing SOC, but its magnitude and nature remain debated.

Purpose of the Study:

• To quantitatively probe and determine the strength of induced spin-orbit coupling (SOC) in graphene-on-WSe2 heterostructures.
• To establish quasiparticle interference imaging as a viable method for SOC characterization.

Main Methods:

• Utilizing scanning tunneling microscopy to image quasiparticle interference patterns in graphene-WSe2.
• Performing theoretical analysis on the Fourier transform of interference images to extract SOC parameters.
• Comparing results with a control sample (30-degree twist angle) lacking backscattering.

Main Results:

• The induced SOC comprises valley-Zeeman (λvZ ≈ 2 meV) and Rashba (λR ≈ 15 meV) terms.
• The measured SOC strength is an order of magnitude larger than theoretical predictions but aligns with prior transport experiments.
• Absence of backscattering in the 30-degree twisted sample validates the methodology.

Conclusions:

• Quasiparticle interference imaging provides a quantitative method to determine SOC in graphene heterostructures.
• The findings offer crucial insights into the mechanisms and strength of SOC in these systems.
• This technique can guide the development of novel spintronic devices and topological materials.