Strong interlayer coupling and stable topological flat bands in twisted bilayer photonic Moiré superlattices

• DOI: 10.1038/s41377-022-00977-4
• Publication Date: 2022-10-06T06:12:47Z
• Authors: Chang-Hwan Yi; Hee Chul Park; Moon Jip Park
• Keywords: Condensed Matter - Mesoscale and Nanoscale Physics; FOS: Physical sciences; QC350-467; Optics. Light; 01 natural sciences; Article; TA1501-1820; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); 0103 physical sciences; Applied optics. Photonics; Physics - Optics; Optics (physics.optics)

AbstractThe moiré superlattice of misaligned atomic bilayers paves the way for designing a new class of materials with wide tunability. In this work, we propose a photonic analog of the moiré superlattice based on dielectric resonator quasi-atoms. In sharp contrast to van der Waals materials with weak interlayer coupling, we realize the strong coupling regime in a moiré superlattice, characterized by cascades of robust flat bands at large twist-angles. Surprisingly, we find that these flat bands are characterized by a non-trivial band topology, the origin of which is the moiré pattern of the resonator arrangement. The physical manifestation of the flat band topology is a robust one-dimensional conducting channel on edge, protected by the reflection symmetry of the moiré superlattice. By explicitly breaking the underlying reflection symmetry on the boundary terminations, we show that the first-order topological edge modes naturally deform into higher-order topological corner modes. Our work pioneers the physics of topological phases in the designable platform of photonic moiré superlattices beyond the weakly coupled regime.