Weyl Points and Fermi Arc Surface States in a Self-assemblable Zinc-Blende Photonic Crystal

Abstract

Colloidal self-assembly has long been proposed as a method for growing large-scale three-dimensional photonic crystals with important optical properties in visible and near-infrared wavelength regimes, where top down lithographic fabrication fails. While much of the focus in these systems has been on producing a photonic band gap, such lattices can also give rise to topological features of photonic bands. To date, there has been no proposal for realizing topological photonic features in photonic crystals that may be self-assembled. In 3D, Weyl points are topological band degeneracies that are of particular interest due to their robustness to perturbations and their corresponding Fermi arc surface states. In order to realize Weyl points, either time-reversal or inversion symmetry must be broken, and no previous self-assembled colloidal photonic crystal has exhibited either property. Here, we propose a new zinc-blende structure, built off of recent progress in self-assembling diamond photonic crystals, which lacks inversion symmetry and supports photonic Weyl points. Furthermore, we show that the geometry can be optimized to make the Weyl point and its Fermi arc surface states experimentally observable in the photonic crystal's projected band structure. Finally, we perform molecular dynamics simulations to demonstrate that the geometry we propose for observing Weyl points is capable of being self-assembled with realistic interparticle interactions. Together, these results provide a platform for the assembly of large-scale photonic crystals supporting topological degeneracies and robust Fermi arc surface states in the visible and near-infrared.