Recently, we investigated the photodetection properties of graphene devices for optical communication light [2]. We demonstrated a gate-tunable zero-bias switching cycle operation and revealed that the dominant photoresponse mechanism is the photo-thermoelectric effect. This provides guidelines for high-performance optoelectronic devices. We also study topological properties in graphene-based supermoiré systems where two moiré patterns are overlaid. By employing lateral and torsional force microscopy, we visualized the atomic lattice, individual moiré pattern, and supermoiré structure.

Stacking structures of two-dimensional materials with certain conditions form a moiré pattern and exhibit emergent phenomena related to electron correlations/topology beyond the original band structure of parent layers. We are exploring quantum transport properties and device functionalities in such structures. We especially focus on a bilayer graphene/hexagonal boron nitride moiré superlattice, which is one of the textbook examples of gapped Dirac materials [1].