Induced Spin-Orbit Interactions in Graphene Quantum Devices

Graphene is a semimetal, but can become a semiconductor in case of bilayer graphene (BLG). High-quality quantum dots can be prepared in gate-defined bilayer graphene. Spin, charge and valley states have been experimentally characterized and the intrinsically weak spin−orbit coupling (SOC) in graphene has been measured in a number of experiments. Integrating BLG with transition metal dichalcogenides (TMDs) enhances the spin−orbit coupling SOC via proximity effects. While this enhancement has been demonstrated in 2D-layered structures, we focus on 1D and 0D nanostructures in BLG/TMD using quantum point contacts and quantum dots in BLG/WSe₂ heterostructures with different stacking orders. Across multiple devices, we reproducibly demonstrate spin−orbit splitting up to 1.5 meV which is more than 1 order of magnitude higher than in pristine graphene. Furthermore, we show that the induced SOC can be tuned in situ from its maximum value to near-complete suppression via a perpendicular electric field. This enhancement and in situ tunability establish SOC as a control mechanism for dynamic spin and valley manipulation.

The experimental work was done in collaboration with Jonas Gerber, Tijl De Groote, Efe Ersoy, Christoph Adam, Artem Denisov, Wister Huang, Michele Masseroni, Markus Niese, Lara Ostertag, Max Ruckriegel, Hadrien Duprez, Lisa Gächter, Chuyao Tong, Rebekka Garreis, and Thomas Ihn. Theory support by Y. Meir, V. Falko and A Knothe is acknowledged.