Correlation Effect in ABC-TLG and hBN Superlattice Revealed by Infrared Photocurrent Spectroscopy

摘要: The moiré superlattice formed by rhombohedral (ABC) stacked trilayer graphene on hexagonal boron nitride is a new playground for correlated physics, featuring tunable Mott insulators, superconductivity, and correlated Chern insulators. Here, we report a spectroscopy study of this system, using the Fourier-transform infrared (FTIR) photocurrent spectroscopy technique. We measured the interband optical transitions between moiré mini bands as a function of vertical displacement field tuned by gate voltages. A continuous evolution of bandgap and bandwidth was observed. We also observed the transitions across the Mott gap at 1/2 filling of the flat band, indicating an onsite Coulomb repulsion of~ 20 meV.