Manipulating Type-I and Type-II Dirac Polaritons in Cavity-Embedded Honeycomb Metasurfaces

Abstract

Pseudorelativistic Dirac quasiparticles have emerged in a plethora of artificial graphene systems that mimic the underlying honeycomb symmetry of graphene. However, it is notoriously difficult to manipulate their properties without modifying the lattice structure. Here we theoretically investigate polaritons supported by honeycomb metasurfaces and, despite the trivial nature of the resonant elements, we unveil rich Dirac physics stemming from a non-trivial winding in the light-matter interaction. A new kind of type-II Dirac point emerges which simultaneously exists with its conventional type-I counterpart. By modifying only the photonic environment via an enclosing cavity, one can manipulate the location of the type-II Dirac points, leading to distinct polariton phases. This enables one to alter the fundamental properties of the emergent Dirac polaritons while preserving the lattice structure—a unique scenario which has no analog in real or artificial graphene systems so far. Exploiting the photonic environment will thus give rise to unexplored Dirac physics at the subwavelength scale.