Theory of quantum oscillations in quasicrystals: Quantizing spiral Fermi surfaces

We show that electronic materials with disallowed rotational symmetries that enforce quasiperiodic order can exhibit quantum oscillations and that these are generically associated with exotic "spiral Fermi surfaces." These Fermi surfaces are self-intersecting, and characterized by a winding number of their surface tangent---a topological invariant---that is larger than one. We compute the nature of the quantum oscillations in two experimentally relevant settings which give rise to spiral Fermi surfaces: a "nearly-free-electron" quasicrystal, and \ang{30} twisted bilayer graphene.