Observation of sublattice polarization and inter-valley coherence in helical trilayer graphene

Helically twisted trilayer graphene (HTG) with the twist near the magic-angle value of 1.8 degrees hosts a variety of correlated insulating states, including, most prominently, the anomalous Hall state. The combination of helical twisting and relaxation in the material is predicted to result in a tiling of supermoire domains that locally host topological bands with opposite Chern numbers, calling for investigations with local probes. Here, we utilize scanning tunneling microscopy and spectroscopy (STM/STS) to study magic-angle HTG. The atomically resolved local density of states maps reveal a cascade of transitions between sublattice-polarized states across the accessible range of filling factors. Moreover, gate-dependent local spectroscopy shows well-developed gaps at quarter- and half-filling of the conduction band. The half-filling gap is characterized by the interplay between inter-valley coherence, as evidenced by the Kekulé reconstruction, and sublattice polarization. Our measurements advance the understanding of the interplay between strong correlation effects and topological band reconstruction in magic-angle HTG.