Two-dimensional moiré superlattices, formed by stacking atomically thin crystals with slight rotational misalignment, provide a powerful platform for engineering emergent electronic phenomena.
Here, we demonstrate that incorporating lead iodide (PbI₂), a layered semiconductor with strong spin–orbit coupling, significantly enriches the physics of such systems. We fabricate a van der Waals heterostructure consisting of four PbI₂ layers beneath hexagonal boron nitride and graphene, with controlled rotational alignment. Unlike conventional graphene-based heterostructures, which exhibit insulating behavior at the charge neutrality point (CNP), our device shows nearly dissipationless transport under high magnetic fields. We observe a robust fractional quantum Hall conductance plateau at 2/3 e²/h, along with quantum interference effects. These findings indicate the emergence of strongly correlated electronic states and suggest that moiré-induced modifications, combined with proximity-enhanced spin–orbit coupling, stabilize a high-field topological insulating phase and enable ballistic electron transport.
Reference
Yan Sun, M. Monteverde, V. Derkach, K. Watanabe, T. Taniguchi, F. Chiodi, H. Bouchiat, and A. D. Chepelianskii, Chern junctions in moiré-patterned graphene/PbI2, Phys. Rev. B 113, 155425 (2026).[arXiv/2508.04935]