Plasmon modes of topological-state networks in twisted bilayer graphene*

We study surface plasmons in minimally twisted bilayer graphene that develops a triangular network of partial dislocations (or AB-BA domain walls) hosting one-dimensional electronic states. We formulate a theoretical model describing propagation of plasmons along one-dimensional links and their scattering at the nodes of such a network. Our model predicts plasmonic spectra composed of multiple bands quasi-periodic in frequency. Due to the long-range Coulomb interaction between neighboring links, the scattering amplitudes have an oscillatory dependence on the node geometry. Therefore, they can be controlled by an applied mechanical strain. We discuss optical nano-imaging experiments that can verify our predictions.