Double exchange, itinerant ferromagnetism and topological Hall effect in moiré heterobilayer

Motivated by the recent experiments and the wide tunability on the MoTe${}_2$/WSe${}_2$ moiré heterobilayer, we consider a physical model to explore the underlying physics for the interplay between the itinerant carriers and the local magnetic moments. In the regime where the MoTe${}_2$ is tuned to a triangular lattice Mott insulator and the WSe${}_2$ layer is doped with the itinerant holes, we invoke the itinerant ferromagnetism from the double exchange mechanism for the itinerant holes on the WSe${}_2$ layer and the local moments on the MoTe${}_2$ layer. Together with the antiferromagnetic exchange on the MoTe${}_2$ layer, the itinerant ferromagnetism generates the scalar spin chirality distribution in the system. We further point out the presence of spin-assisted hopping in addition to the Kondo coupling between the local spin and the itinerant holes, and demonstrate the topological Hall effect for the itinerant electrons in the presence of the non-collinear spin configurations. This work may improve our understanding of the correlated moiré systems and inspire further experimental efforts.