Imaging Supermoire Relaxation in Helical Trilayer Graphene: Part II

Helical trilayer graphene (HTG) relaxes into a superstructure of large triangular domains with uniform moiré periodicity that are separated by a network of boundaries where the stacking configuration changes. These domain walls are predicted to host valley-contrasting topological modes when the domains are gapped. In this talk, I will describe measurements that resolve the local conductance in HTG with a scanning single-electron transistor (SET). We show enhanced conductance along the domain wall network, consistent with the prediction of helical edge modes. Simulations that combine theoretical calculations with an electrostatic model for the finite resolution of the SET tip show good agreement with our measurements, consistent with a supermoire network of gapless topological boundary modes. The ability to enhance and reshape domains with strain establishes HTG as a promising platform to engineer tunable correlated topological networks.