Disentangled Higher-Orbital Bands and Chiral Symmetric Topology in Confined Mie Resonance Photonic Crystals

Topological phases based on tight-binding models have been extensively studied in recent decades. By mimicking the linear combination of atomic orbitals in tight-binding models based on the evanescent couplings between resonators in classical waves, numerous experimental demonstrations of topological phases have been successfully conducted. However, in dielectric photonic crystals, the Mie resonances' states decay too slowly as 1/r$1/r$, leading to intrinsically different physics between tight-binding models and dielectric photonic crystals. Here, a confined Mie resonance photonic crystal is proposed by embedding perfect electric conductors between dielectric rods, creating the chiral symmetric band structure which ideally matches tight-binding models with nearest-neighbour couplings. As a consequence, disentangled band structure spanned by higher atomic orbitals is observed. Moreover, the result provides an effective route to achieve a 3D photonic crystal with a complete photonic bandgap and third-order topology. The implementation offers a versatile platform for studying exotic higher-orbital bands and achieving tight-binding-like 3D topological photonic crystals. A new family of photonic crystals is proposed by using metals to confine Mie resonance mode, achieving photonic tight-binding models with chiral symmetry. The conventional entangled band structure at the high frequency is now disentangled. A 3D higher-order topological photonic crystal is achieved with a large complete bandgap. These findings offer new possibilities to explore exotic photonic tight-binding models.image