Topological Kondo semimetal and insulator in AB-stacked heterobilayer transition metal dichalcogenides

Recent experiments reported the realization of a heavy Fermi liquid in AB-stacked MoTe2/WSe2 heterobilayers. In this paper, we show that the AB-stacked heterobilayer configuration is particularly suited to realize topological Kondo semimetal and topological Kondo insulator ground states at a doping of two holes per moiré unit cell. The small lattice mismatch between the MoTe2 and WSe2 monolayers and the different bandwidths of their highest lying moiré valence bands means that, in the experimentally relevant range of hole dopings, the MoTe2 layer is effectively a Mott insulator with only low-lying magnetic excitations Kondo-coupled to more itinerant electrons in the WSe2. The crucial consequence of the AB-stacking configuration is that the interlayer tunneling connects orbitals of opposite parity in the two layers, leading to a chiral Kondo coupling. We show that the chiral Kondo coupling favors a topological Kondo semimetal at filling ν=1+1, with a nonquantized spin Hall conductance arising from edge modes, whose spectrum and overlap with bulk states we determine. We further show that a spatially random strain field that locally breaks the rotation symmetry can convert the Kondo semimetal to a narrow gap topological Kondo insulator featuring a quantized spin Hall conductance.