Direct Observation of Dirac Cones and a Flatband in a Honeycomb Lattice for Polaritons

TLDR

Two‑dimensional lattices of coupled micropillars etched in a planar semiconductor microcavity provide a versatile platform for engineering polariton band structures. We report experimental studies of honeycomb lattices in which the low‑energy polariton dispersion mimics that of electrons in graphene. Using energy‑resolved photoluminescence, we directly observe Dirac cones, with polariton dynamics described by the Dirac equation for massless particles. We detect Dirac cones, p‑orbital bands including a flatband, and a structure supporting massless, massive, and infinitely massive polaritons, opening avenues to study dispersion, interactions, and frustration.

Abstract

Two-dimensional lattices of coupled micropillars etched in a planar semiconductor microcavity offer a workbench to engineer the band structure of polaritons. We report experimental studies of honeycomb lattices where the polariton low-energy dispersion is analogous to that of electrons in graphene. Using energy-resolved photoluminescence, we directly observe Dirac cones, around which the dynamics of polaritons is described by the Dirac equation for massless particles. At higher energies, we observe $p$ orbital bands, one of them with the nondispersive character of a flatband. The realization of this structure which holds massless, massive, and infinitely massive particles opens the route towards studies of the interplay of dispersion, interactions, and frustration in a novel and controlled environment.