Near-field optical characterization of atomic structures and polaritons in twisted two-dimensional materials br

Polariton is a quasiparticle generated from strong interaction between a photon and an electric or magneticdipole-carrying excitation. These polaritons can confine light into a small space that is beyond the diffractionlimit of light, thus have greatly advanced the development of nano photonics, nonlinear optics, quantum opticsand other related research. Van der Waals two-dimensional (2D) crystals provide an ideal platform for studyingnano-polaritons due to reduced material dimensionality. In particular, stacking and twisting offer additionaldegree of freedom for manipulating polaritons that are not available in a single-layer material. In this paper, wereview the near-field optical characterizations of various structures and polaritonic properties of stacked/twisted2D crystals reported in recent years, including domain structures of stacked few-layer graphene, moiresuperlattice structures of twisted 2D crystals, twisted topological polaritons, and twisted chiral plasmons. Wealso propose several exciting directions for future study of polaritons in stacked/twisted 2D crystals