  Over the past decade, topology has garnered great attention in a wide area of
physics. In particular, it has exerted influence on photonics because carefully
engineered photonic crystals and metamaterials can help explore the non-trivial
state of materials. In this regard, all dielectric metamaterials with large
anisotropy, and dipole and multipole Mie resonators have played an increasingly
important role in topological photonics. Advantages of Mie resonators make it
possible to quest for non-trivial states in three dimensions and theoretical
calculation supports its potential. However, it is very difficult to
demonstrate this experimentally because it is hard to make the metacrystal by
anisotropic meta-atoms despite much effort. Here we report a Dirac metamaterial
for 3D topological photonics. It is implemented by a metacrystal self-assembled
by a molecule, HYLION-12 which has both anisotropic polarizability and ring
current. As its peculiar properties, it has an exotic optical constant that can
be used for the electric and magnetic hyperbolic metamaterial, and the double
hyperbolic metamaterial in the ultraviolet region. It also showed 142% of
reflectance at 242nm as an amplified reflector and asymmetric transmittance up
to 30% through the opaque substrate as a Huygens source under 300nm.
Furthermore, it demonstrated various phenomena of topological photonics such as
Pancharatnam-Berry and waveguide phase merging, wavefront shaping and waveguide
on edges as a 3D topological photonic material. The new strategy using
polyaromatic hydrocarbons (PAHs) is expected to be an effective way to realize
3D topological photonics.
