Observation of Photonic Landau Levels in Strained Honeycomb Lattices

Abstract

We report the realization of a synthetic magnetic field for photons and polaritons in a honeycomb lattice of coupled semiconductor micropillars. A strong synthetic field is induced both in s and p orbital bands by engineering a uniaxial hopping gradient in the lattice, giving rise to the formation of Landau levels at the Dirac points. We provide direct evidence of the sublattice symmetry breaking of the lowest order Landau level wavefunction, a distinctive feature of synthetic magnetic fields. Our realization implements helical edge states in the gap between n = 0 and n = ±1 Landau levels demonstrating experimentally a novel way of engineering propagating edge states in photonic lattices. In the light of recent advances on the enhancement of polariton-polariton nonlinearities, the highly degenerate Landau levels here reported are promising for the study of strongly correlated photonic phases.