Band Gap Optimization of Colloidal MgCu₂ Photonic Crystals

It was recently shown that a colloidal MgCu₂ lattice can be self-assembled using a combination of DNA coated spheres and compressed tetrahedral clusters of spheres. The spheres and compressed clusters form two interpenetrating sublattices, diamond and pyrochlore, respectively. Both sublattices have a photonic band gap. We calculate the photonic band structures of the compressed cluster crystals, which differ from those of the standard pyrochlore lattice that has been considered previously. We find that the compression of the clusters can make the band gap significantly wider than for the typical pyrochlore lattices. We can precisely tune the compression of our synthesized tetrahedral clusters, giving us the opportunity to explore the full range of MgCu₂ assembly and optimize their photonic properties.