Site-selective insulating phase in twisted bilayer Hubbard model

The paramagnetic phase diagrams of the half-filled Hubbard model on a twisted bilayer square lattice are investigated using coherent potential approximation. Besides the conventional metallic, band insulating, and Mott insulating phases, we find two site-selective insulating phases where certain sites exhibit band insulating behaviors while the others display Mott insulating behaviors. These phases are identified by the band gap, the double occupancy, the density of states, as well as the imaginary part of self-energy. Furthermore, we examine the effect of on-site potential on the stability of the site-selective insulating phases. Our results indicate that fruitful site-selective phases can be engineered by twisting.