Determination of proximity-induced spin-orbit coupling in monolayer graphene-WSe₂ heterostructures using large-index Landau level crossings

Supporting graphene flat band systems on WSe₂ substrates is known to alter the delicate interplay of isospin symmetry-broken phases and favor superconducting states. While these findings are generally attributed to the proximity induced spin orbit coupling, the precise nature of the induced coupling has remained elusive. Specifically, while the role of Ising-type spin-orbit coupling is well-understood and can be accurately measured in some cases[1-3], prior estimates for the induced Rashba-type range over at least one order of magnitude. Here, we use high-index Landau level coincidences in ultra-clean monolayer graphene devices to extract an accurate measurement of both the Ising and Rashba spin-orbit coupling induced by a monolayer WSe₂ substrate. Our central result is that the Rashba SOC is in the 5K range in all devices, considerably smaller than what has been assumed in much of the experimental literature but consistent with recent ab initio theoretical predictions [4]. Our results sharply constrain theoretical modeling of graphene-WSe₂ systems, especially on Cooper-pair breaking phenomena which can be impacted by even a small Rashba SOC.

[1] Island, J.O., et. al. Nature 571, 85–89.

[2] Zhang, Y., et al. Nature 613, 268–273.

[3] Holleis, L., et. al. arXiv:2303.00742v1.

[4] Li, Y., Koshino, M. Phys Rev B 99.