Atomic-scale thermoelectric imaging of sublattice symmetry in epitaxial bilayer graphene

Abstract Probing and controlling the stacking order in two-dimensional materials such as graphene and transition metal dichalcogenides plays a critical role in tailoring Moiré bands, band gaps, and associated emergent physical properties. Here, we investigate how stacking-order variations manifest as domains and domain boundaries in epitaxial bilayer graphene, and how these structures are linked to sublattice symmetry at the atomic scale. Using scanning thermoelectric microscopy, we resolve triangular sublattice contrast within Bernal-stacked domains and directly observe its inversion across neighboring regions. At the intervening domain boundaries, the contrast diminishes, indicating restoration of sublattice symmetry through an intermediate AA-type stacking. First-principles calculations of the electronic structure and thermoelectric power reproduce the observed sublattice contrast and predict topological edge states at the domain boundary. These results demonstrate that thermoelectric imaging enables real-space, atomic-resolution probing of stacking-dependent electronic states and the accompanying changes in sublattice symmetry. Moreover, this approach is expected to provide new opportunities for investigating the physical properties of van der Waals multilayer systems.