Photocurrent spectroscopy study of the gap opening in graphene/hBN moiré superlattice

Moiré superlattice composed of van der Waals materials has recently been explored as a promising platform for the study and engineering of electron correlation and topological phenomena. Graphene/hBN moiré superlattice, one of the simplest two-dimensional moiré systems, serves as a great example to understand the effect of moiré potential. In this system, the semi-metallic graphene will open up a gap at the charge neutrality point because of the symmetry breaking induced by the moiré superlattice, which has been extensively investigated by transport measurement previously. Here, I will present our study of the gap opening in graphene/hBN moiré system by photocurrent spectroscopy. Several spectroscopic approaches to accurately determine the gap may refresh our understanding of the gap opening, and give us more insights on the various exotic phenomena in the moiré systems.