Moiré band topology in twisted bilayer graphene*

Recently twisted bilayer graphene (t-BLG) emerges as a strongly correlated physical platform near a magic twist angle, hosting the Mott-like insulating phases and unconventional superconducting behavior. Besides, band topology may be another critical element in strongly correlated twistronics. In this work, we performed a systematic nonlocal transport study and revealed the nontrivial moiré band topology in t-BLG. Pronounced nonlocal responses are observed both in the electron and hole superlattice gaps of t-BLG, which are robust to the interlayer electric field, twist angle, and edge termination. We elucidate that two nontrivial Z₂ invariants characterize the topology of the moiré bands. Our findings provide a new perspective for understanding the emerging strongly correlated phenomena in twisted van der Waals heterostructures.