Correlated insulating states in the Γ valley of twisted MoSe₂ bilayer

When two identical layers of transition metal dichalcogenides (TMDs) are stacked with a small twist angle, a moiré superlattice is formed, folding the original band structure into moiré flat bands, where the quasiparticle’s kinetic energy becomes comparable to the Coulomb interaction. Since many parameters including the superlattice constant and filling number are controllable, moiré materials have become a promising platform for simulating quantum many-body effects in two dimensions. So far, much effort has been focused on moiré flat bands in the K valley of twisted TMDs, where the complex coupling gives rise to a plethora of exotic properties. In this work, we focus on the moiré flat bands in the Γ valley of a twisted MoSe₂ bilayer. With minimal spin-orbit coupling, the single-body Hamiltonian is similar to that in graphene, but with a significantly reduced Fermi velocity. We observe energy gaps opening at the Dirac point and other integer and fractional fillings, leading to insulating behavior at low temperatures. The correlated insulating states are optically probed using the exciton sensing technique. Finally, we discuss the spin coupling in some of these states.