Direct observation of photonic Landau levels and helical edge states 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 in both the 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, experimentally demonstrating a novel way of engineering propagating edge states in photonic lattices. In light of recent advances in the enhancement of polariton–polariton nonlinearities, the Landau levels reported here are promising for the study of the interplay between pseudomagnetism and interactions in a photonic system.

Polariton spin jets through optical control

“…The system's dependencies on the polarization of the excitation laser under various spin-coupling circumstances has been extensively studied for polariton condensates in optical (laser induced) traps [9-12, 15, 24, 29] and in fabricated patterned photonic lattices [14,35,36]. However, extended systems of highly energetic ballistically expanding polariton condensates [37][38][39], which possess their own unique physical properties [38], have not been properly explored in terms of spin.…”

Strain induced localization to delocalization transition on a Lieb photonic ribbon lattice

“…In the latter system, a predicted semi-Dirac scenario arises in graphene at a critical compression, which produces a highly anisotropic transport and particular localization features. Remarkable also, it has been experimentally shown in graphene photonic lattices that a smart design in term of compression or strain could induce a pseudomagnetic field, causing the rupture of Dirac cones and the appearance of Landau levels in the band structure 19 – 21 , which constitutes a clear delocalization–localization transition.…”

Strain-induced Localization-delocalization Transition on a Lieb Ribbon Lattice

“…In the latter system, a predicted semi-Dirac scenario arises in graphene at a critical compression, which produces a highly anisotropic transport and particular localization features. Remarkable also, it has been experimentally shown in graphene photonic lattices that a smart design in term of compression or strain could induce a pseudomagnetic field, causing the rupture of Dirac cones and the appearance of Landau levels in the band structure [19][20][21] , which constitutes a clear delocalization-localization transition.…”