CM Seminar - The magic of twisted bilayer graphene with spin-orbit coupling

Abstract: Stacking two graphene layers twisted by the ‘magic angle’ 1.1º generates flat energy bands, which, in turn, catalyzes various correlated phenomena depending on filling and sample details. The importance of the `magic’ angle, however, has recently been challenged by experiments that observe superconductivity in twisted bilayer graphene with a WSe2 substrate at twist angles as low as 0.8°. I argue that the primary direct effect of WSe2 is to induce spin orbit coupling in the graphene monolayer immediately adjacent to it and discuss some topological features of the band structure close to the magic angle. Importantly, with the introduction of spin orbit coupling, all of the ingredients needed for the emergence of non-abelian anyons, the key components to certain implementations of topological quantum computation, are found intrinsically within this single system. I bring these ingredients together in a proposal for the realization of Majoranas in twisted bilayer graphene and outline some of the challenges that lie ahead.

A short bio: Alex Thomson received her PhD from Harvard University in 2018. She is currently a Sherman Fairchild Postdoctoral Scholar at the California Institute of Technology. Her current focus on understanding the phenomenology of twisted graphene heterostructures and transition metal dichalcogenides; more generally, she has an interest in strongly correlated physics and disorder.