Chiral Propagation of Plasmon Polaritons due to Competing Anisotropies in a Twisted Photonic Heterostructure

We theoretically demonstrate chiral propagation of plasmon polaritons and show that it is more efficient and easier to control than the recently observed chiral shear phonon polaritons. We consider plasmon polaritons created in an anisotropic two-dimensional (2D) material twisted with respect to an anisotropic substrate to best exploit the competition between anisotropic electron-electron interactions and the anisotropic electronic structure of the host material. Gate voltage and twist angle are then used for precise control of the chiral plasmon polaritons, overcoming the existing restrictions with chiral phonon polaritons. These findings open feasible opportunities for efficient and tunable plasmon-based nanophotonics and compact, high-performance on-chip optical devices.