Ultra-strong spin-orbit coupling and topological moire engineering in twisted ZrS₂ bilayers

Pioneering experiments in twisted bilayer graphene and group-VI transition-metal dichalcogenide (TMD) heterostructures pave the way towards leveraging quantum interference in moiré superlattices as a broader paradigm, to quench kinetic energy scales and selectively enhance the role of competing interactions. Here, we propose twisted bilayers of the group-IV TMD ZrS₂ as a tunable platform to engineer two-dimensional topological quantum phases, instead dominated by strong spin-orbit interactions. At small twist angles, ZrS₂ heterostructures give rise to an emergent and twist-controlled moiré Kagomé lattice, combining geometric frustration and strong spin-orbit coupling to give rise to a moiré quantum spin Hall insulator with highly controllable and nearly-dispersionless bands. We study the emergence of a robust quantum anomalous Hall phase as well as possible fractional Chern insulating states from strong Coulomb repulsion at fractional fillings of the topological moiré Kagomé bands. Our results establish group-IV transition metal dichalcogenide bilayers as a novel moiré platform to realize strongly-correlated topological phases in a twist-tunable setting.