Observation of Kondo Insulator State in a Transition Metal Dichalcogenide Moiré Superlattice

Kondo insulator is the ground state of a Kondo lattice when an itinerant electron is tightly bound with a localized moment in the strong coupling limit. Recent developments in the study of moiré superlattice of transition metal dichalcogenides (TMDs) heterostructures provide a flexible platform to study Kondo physics in two-dimensions. Here we report an emerging Kondo insulator phase in a moiré structure based on WS₂ and WSe₂. Using dual gate geometry, the moiré band is doped to half filling on the hole side, forming a Kondo lattice, while additional carriers are doped into another layer at the same density, acting as itinerant electrons. We probe the formation of the insulating state by microwave impedance microscopy (MIM) measurement. We find that the Kondo insulator phase extends to a wide range of electric fields and further characterize its evolution with varying temperatures and magnetic fields.