“He reckoned the moiré cell itself would have one property that varied strictly with rotation angle, more or less independently of the details of the atoms that made it up. That property was a critical one: the amount of energy a free electron in the cell would have to gain or shed to tunnel between the two graphene sheets. That energy difference was usually enough to serve as a barrier to intersheet tunneling. But MacDonald calculated that as the rotation angle narrowed from a larger one, the tunneling energy would shrink, finally disappearing altogether at exactly 1.1 degrees.”