Correlated and topological states in twisted bilayer-trilayer graphene

Moiré patterns have opened up many new avenues of study in van der Waals materials owing to their ability to generate flat bands with nontrivial topology. So far, the investigation of graphene-based moiré systems has been limited to twisted structures comprising only monolayers and bilayers of graphene. Here, we investigate a larger family of twisted M+N graphene multilayers, created by stacking and rotating M- and N-layer Bernal graphene sheets. We observe correlated and topological states with striking commonalities across many different structures in the ultra-thin limit (e.g., t1+2, t2+2, t1+3, t2+3, etc), owing to a close resemblance of their moiré flat bands. We find that twisted bilayer-trilayer graphene exhibits a particularly rich correlated phase diagram, manifesting a wide array of symmetry-broken states at partial filling of both the valence and conduction moiré minibands. We observe an anomalous Hall effect upon filling one electron per moiré unit cell, pointing to the emergence of orbital magnetism in a topological band. Additional correlated states emerge upon applying a perpendicular magnetic field. Overall, our work points towards a common understanding of the correlated phase diagram across a wide variety of twisted graphene multilayer structures.