Moiré Structure and Band Alignment in Gate-Tunable WSe₂/MoSe₂ Heterostructures

Monolayer transition metal dichalcogenide (e.g., MoSe₂, WSe₂, MoS₂, WS₂) semiconductors have received massive attention since they were discovered to form moiré superlattices. When stacked, a ~0.1% lattice mismatch causes periodic modulation of the bands resulting in trapped moiré excitons in the potential minima. Twist angles near 0 and 60 degrees create moiré flat bands and the interplay of these bands with long-range Coulomb interactions is predicted to create novel correlated quantum phenomena. To date, there is limited work exploring moiré physics in MoSe₂/WSe₂ heterostructures and the investigations show conflicting results. Here we use fabricated graphene nanoribbons placed underneath the heterostructure as contact electrodes and a silicon substrate as a back gate to control the device carrier density. We probe a WSe₂/MoSe₂ heterostructure near a 0-degree twist angle using scanning tunnel microscopy and spectroscopy (STM/S) and report changes of the moiré structure and band alignment with carrier density.