Photonic Flat Landau Levels Induced by Antisymmetric Nonuniform Pseudomagnetic Fields

Pseudomagnetic fields (PMFs) have been proven useful for generating Landau levels and controlling wave propagation in classical wave systems. Recently, photonic flat Landau levels residing near the K and K^{'} points induced by PMFs have been realized through uniaxial gradient deformations of superlattices. Here, we report the realization of flat Landau levels near the Γ point in Dirac photonic crystals with wider-range uniaxial gradient deformations, induced by antisymmetric, nonuniform PMFs. The flat Landau levels appear as spatially localized, doubly degenerate bulk modes, and are associated with dispersive valley kink modes. The nonuniform PMF distributions provide an additional degree of freedom that can enhance the flatness of flat Landau levels that extends for an expanded k-space range. We experimentally visualized the band dispersion of flat Landau levels and observed both localized flat Landau level modes and chiral valley kink modes. Our results pave a new avenue for manipulating electromagnetic wave localization and transport via PMFs.