Moire-induced bandgap tuning by varying electric dipole in InSe/CuSe vertical heterostructure

The stacked two layered materials with a lattice constant mismatch and/or with a twist angle relative to each other can create a moire pattern, modulating electronic properties of pristine materials. Here, we combine scanning tunneling microscopy/spectroscopy and density functional theory calculations to investigate the moire potential induced bandgap tuning in an InSe/CuSe vertical heterostructure synthesized by a two-step of molecular beam epitaxy. Scanning tunneling microscopy measurements demonstrate the heterostructure with a superlattice periodicity of similar to 3.48 nm and a twist angle of about 11 degrees between the monolayers. Scanning tunneling spectroscopy record on the different stacking sites of the heterostructure reveals the bandgap of the InSe is location-dependent and a variation of 400 meV is observed. Density functional theory calculations reveal that the moire-induce electric dipole in the monolayer InSe is the key factor for tuning the bandgap. Moreover, charge transfer between CuSe and InSe also contributes to the bandgap variation due to its stacking. We also show that the moire potential not only can tune the bandgap of InSe but also can vanish the Dirac nodal line of CuSe in some stackings. Our explorations provide valuable information in understanding electronic properties of two-dimensional moire materials.