Physics Colloquium: Michael Fogler (UCSD): Collective modes of twisted van der Waals material
Collective modes of twisted van der Waals materials
Michael Fogler Professor Department of Physics, University of California San Diego
Rotationally misalignment profoundly modifies electronic and lattice properties of van der Waals materials. If the twist angle between adjacent layers is small, a periodic network of dislocations (solitons) delineating large commensurate domains appears. These solitons have a surprisingly strong influence on collective modes of the system, plasmons and phonon-polaritons. For example, a twisted bilayer graphene can act as a photonic crystal for two- and one-dimensional plasmons. Solitons in a twisted boron nitride can induce spectral shift and splitting of phonon-polaritons. I will review recent nano-optical experiments that probed these phenomena andtheir theoretical modeling.
 G. X. Ni et al., Soliton superlattices in twisted hexagonal boron nitride, Nature Comm. 10, 4360 (2019).
 S. S. Sunku et al., Photonic crystals for nano-light in moire graphene superlattices. Science 362, 1153-1156 (2018).
 B.-Y. Jiang et al., Plasmon reflections by topological electronic boundaries in bilayer graphene. Nano Lett, 17, 7080-7085 (2017).
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