Flat bands and perfect metal in trilayer moir\'e graphene

Understand

We investigate the electronic structure of a twisted multilayer graphene system forming a moir\'e pattern.

• We consider small twist angles separating the graphene sheets and develop a low-energy theory to describe the coupling of Dirac Bloch states close to the K point in each individual plane.
• Extending beyond the bilayer case, we show that, when the ratio of the consecutive twist angles is rational, a periodicity emerges in quasimomentum space with moir\'e Bloch bands even when the system does not exhibit a crystalline lattice structure in real space.
• For a trilayer geometry, we find flat bands in the spectrum at certain rotation angles.