Surface band-selective moiré effect induces flat band in mixed-dimensional heterostructures

Abstract: In this work, we reveal a curious type of moir\'e effect that selectively modifies the surface states of bulk crystal. We synthesize mixed-dimensional heterostructures consisting of a noble gas monolayer grow on the surface of bulk Bi(111), and determine the electronic structure of the heterostructures using angle-resolved photoemission spectroscopy. We directly observe moir\'e replicas of the Bi(111) surface states, while the bulk states remain barely changed. Meanwhile, we achieve control over the moir\'e period in the range of 25 {\AA} to 80 {\AA} by selecting monolayers of different noble gases and adjusting the annealing temperature. At large moir\'e periods, we observe hybridization between the surface band replicas, which leads to the formation of a correlated flat band. Our results serve as a bridge for understanding the moir\'e modulation effect from 2D to 3D systems, and provide a feasible approach for the realization of correlated phenomena through the engineering of surface states via moir\'e effects.