Observation of high-order moiré effect and multiple Dirac fermions replicas in graphene-SiC heterostructures

Moir\'e potential has become a powerful tool to modulate electronic structures and realize quantum phases. Authors of previous studies mainly focused on the first-order moir\'e effect in systems with small lattice mismatches and rotation angles. Here, we report evidence of a high-order moir\'e effect and multiple Dirac cone replicas by performing angle-resolved photoemission spectroscopy on a graphene-SiC heterostructure. Despite that the first-order moir\'e effect is weak due to large lattice mismatch and rotation angle, a high-order moir\'e effect with a 1.9 nm periodicity in real-space is experimentally observed. Different from previously studied first-order moir\'e systems, in which only replicas with momentum transfer by the primitive reciprocal lattice vectors were observed, Dirac cone replicas with momentum transfer by second- and third-order reciprocal lattice vectors are experimentally identified. Our results not only demonstrate the high-order moir\'e effect in a graphene-SiC heterostructure but also provide opportunities to engineer moir\'e systems without the limitation of small lattice constant mismatches.