  It has long been speculated that quasi-two-dimensional superconductivity can
reappear above its semiclassical upper critical field due to Landau
quantization, yet this reentrant property has never been observed. Here, we
argue that twisted bilayer graphene at a magic angle (MATBG) is an ideal system
in which to search for this phenomenon because its Landau levels are doubly
degenerate, and its superconductivity appears already at carrier densities
small enough to allow the quantum limit to be reached at relatively modest
magnetic fields. We study this problem theoretically by combining a simplified
continuum model for the electronic structure of MATBG with a phenomenological
attractive pairing interaction, and discuss obstacles to the observation of
quantum Hall superconductivity presented by disorder, thermal fluctuations, and
competing phases.
