Topological origin of domain-wall boundary modes

Determine whether the quasi-one-dimensional electronic modes localized at helical trilayer graphene supermoiré domain walls have a topological origin and are directly connected to Chern-number inversion across the domain-wall interface.

Background

Helical trilayer graphene exhibits in-gap electronic states that are strongly localized along sharp supermoiré domain walls and absent from domain interiors, indicating the formation of quasi-one-dimensional boundary channels. The adjacent domains contain inverted moiré sublattices, which is consistent with—but does not establish—a reversal of local topological character across the interface.

The measurements reported in the paper do not determine whether these boundary modes are topologically protected or whether they arise from a Chern-number inversion. Magnetic-field-dependent scanning tunneling microscopy and spectroscopy up to 2.5 T also did not resolve a definitive signature of a topological Chern number, leaving the origin of the boundary states unresolved.