Realization of a Kondo Insulator in a Multilayer TMD Moiré Superlattice

Kondo insulators are a strongly correlated electron system, arising from the hybridization between itinerary conduction electrons and localized magnetic moments, which opens a gap in the band of conduction electrons. Traditionally, the known Kondo insulators are found in materials with f-electrons. Recent developments in 2D moiré systems provide a new approach to generate flat bands with strong electron correlation, which host localized moments at half filling. In this work, we demonstrate the realization of a Kondo insulator phase in a moiré superlattice of monolayer WS2 / bilayer WSe2 which hosts a set of moiré flat bands in the WSe2 layer interfacing the WS2 layer and dispersive bands in the other WSe2 layer. When both WSe2 layers are partially doped but with a total density of two holes per moiré unit cell, an insulating state appears when the density of the moiré band is below one hole per moiré unit cell. The insulating state disappears above a certain threshold magnetic field and the system becomes metallic, which is a telltale signature of the Kondo insulator. Our results demonstrate the TMD moiré system as a rich platform to explore correlation-enabled electronic phases.