Evidence of topological Kondo insulating state in MoTe2/WSe2 moiré bilayers

Topological Kondo insulators (TKIs) are topologically protected insulating states induced not by single-particle band inversions, but by the Kondo interaction between itinerant electrons and a lattice of local magnetic moments. Although experiments have suggested the emergence of three-dimensional (3D) TKIs in the rare earth compound SmB6, its two-dimensional (2D) counterpart has not been demonstrated to date. Here we report experimental evidence of a TKI in angle-aligned MoTe2/WSe2 moiré bilayers, which support a Kondo lattice with topologically nontrivial Kondo interactions. We prepare in a dual-gated device a triangular lattice Mott insulator in the MoTe2 layer Kondo-coupled to a half-filled itinerant band in the WSe2 layer. Combined transport and compressibility measurements show that the prepared state supports metallic transport at high temperatures and, at low temperatures, an insulating bulk with conducting helical edge states protected by spin-Sz conservation. The presence of Kondo singlets is further evidenced by their breakdown at high magnetic fields. Such behaviors are in stark contrast to the simple metallic state when the Mott insulator in the MoTe2 layer is depleted by gating. Our results open the door for exploring tunable topological Kondo physics in moiré materials.