Manipulating generalized Dirac cones in subwavelength dipolar arrays

Abstract

We discuss the emergence and manipulation of generalized Dirac cones in the subradiant collective modes of a subwavelength dipolar array. We consider a collection of single quantum emitters modeled as point dipoles arranged in a honeycomb lattice with subwavelength periodicity. While conventional honeycomb arrays host bound modes that display Dirac cones at the K and K′ points, we show that introducing uniaxial anisotropy in the lattice results in modified dispersion relations. These include the tilting of Dirac cones arising purely due to long-range, retarded, electromagnetic coupling in the lattice, which changes the local density of states at the Dirac point from vanishing (type I) to diverging (types II and III), the emergence of semi-Dirac points, with linear and quadratic dispersions in orthogonal directions, and the anisotropic movement of Dirac cones away from the K and K′ points. Such energy dispersions can modify substantially the dynamics of local probes, such as quantum emitters, for which they have been shown to induce anisotropic power-law interactions.