Quantum Hall Effect Measurement of Spin-Orbit Coupling Strengths in Ultraclean Bilayer Graphene/WSe2 Heterostructures

TL;DR

This study uses quantum Hall effect measurements to quantify proximity-induced spin-orbit coupling in ultraclean bilayer graphene/WSe2 heterostructures, revealing significant SOC strengths and layer-dependent effects with implications for topological states.

Contribution

First measurement of proximity-induced SOC in bilayer graphene/WSe2 heterostructures using quantum Hall effect, demonstrating layer-specific SOC and high mobility interfaces.

Findings

Ising SOC ~2.2 meV, much higher than intrinsic graphene SOC

Rashba SOC ~15 meV, indicating strong spin-orbit interaction

Layer-dependent SOC effects observed through Landau level crossings

Abstract

We study proximity-induced spin-orbit coupling (SOC) in bilayer graphene/few-layer WSe2 heterostructure devices. Contact mode atomic force microscopy (AFM) cleaning yields ultra-clean interfaces and high-mobility devices. In a perpendicular magnetic field, we measure the quantum Hall effect to determine the Landau level structure in the presence of out-of-plane Ising and in-plane Rashba SOC. A distinct Landau level crossing pattern emerges when tuning the charge density and displacement field independently with dual gates, originating from a layer-selective SOC proximity effect. Analyzing the Landau level crossings and measured inter-Landau level energy gaps yields the proximity induced SOC energy scale. The Ising SOC is ~ 2.2 meV, 100 times higher than the intrinsic SOC in graphene, while its sign is consistent with theories predicting a dependence of SOC on interlayer twist angle. The Rashba SOC is ~15 meV. Finally, we infer the magnetic field dependence of the inter-Landau level Coulomb interactions. These ultraclean bilayer graphene/WSe2 heterostructures provide a high mobility system with the potential to realize novel topological electronic states and manipulate spins in nanostructures.