Magic configurations in moiré superlattice of bilayer photonic crystals: Almost-perfect flatbands and unconventional localization

We investigate the physics of photonic band structures of the moiré patterns that emerged when overlapping two unidimensional photonic crystal slabs with mismatched periods. The band structure of our system is a result of the interplay between intralayer and interlayer coupling mechanisms, which can be fine-tuned via the distance separating the two layers. We derive an effective Hamiltonian that captures the essential physics of the system and reproduces all numerical simulations of electromagnetic solutions with high accuracy. Most interestingly, magic distances corresponding to the emergence of photonic flatbands within the whole Brillouin zone of the moiré superlattice are observed. We demonstrate that these flatband modes are tightly localized within a moiré period. Moreover, we suggest a single-band tight-binding model that describes the moiré minibands, of which the tunneling rate can be continuously tuned via the interlayer strength. Our results show that the band structure of bilayer photonic moiré can be engineered in the same fashion as the electronic/excitonic counterparts. It would pave the way to study many-body physics at photonic moiré flatbands and optoelectronic devices.