Moire flat bands in twisted 2D hexagonal vdW materials

Moire superlattices (MSL) in twisted bilayer graphene (TBG) and its derived structures can host exotic correlated quantum phenomena because the narrow moire flat minibands in those systems effectively enhance the electron-electron interaction. Correlated phenomena are also observed in 2H-transitional metal dichalcogenides MSL. However, the number of moire systems that have been explored in experiments are still very limited. Here we theoretically investigate a series of two-dimensional (2D) twisted bilayer hexagonal materials beyond TBG at fixed angles of 7.34(circle) and 67.34(circle) with 22 2D van der Waals layered materials that are commonly studied in experiments. First-principles calculations are employed to systemically study the moire minibands in these systems. We find that flat bands with narrow bandwidth generally exist in these systems. Some of the systems such as twisted bilayer In2Se3, InSe, GaSe, GaS and PtS2 even host ultra-flat bands with bandwidth less than 20 meV even for such large angles, which makes them especially appealing for further experimental investigations. We further analysis the characters of moire flat bands and provide guidance for further exploration of 2D MSL that could host strong electron correlations.