Tailoring Dirac Fermions by In-Situ Tunable High-Order Moire acute accent Pattern in Graphene-Monolayer Xenon Heterostructure

We report an experimental study of a high-order moire ' pattern formed in graphene-monolayer xenon heterostructure. The moire ' period is in situ tuned from few nanometers to +co, by adjusting the lattice constant of the xenon monolayer through annealing. Using angle-resolved photoemission spectroscopy, we observe that Dirac node replicas move closer and finally overlap with a gap opening, as the moire ' pattern expands to +co and evolves into a Kekule ' distortion. A moire ' Hamiltonian coupling Dirac fermions from different valleys explains experimental results and indicates narrow moire ' band. Our Letter demonstrates a platform to study continuous evolution of the moire ' pattern, and provides an unprecedented approach for tailoring Dirac fermions with tunable intervalley coupling.