Cubic 3D Chern photonic insulators with orientable large Chern vectors*

A 3D Chern insulator is a Time Reversal Symmetry (TRS) broken topological phase characterized by a vector of three first Chern invariants, associated with the planes supporting topologically protected surface states. In this work, we devise a general strategy to design 3D Chern Insulating (3D CI) cubic Photonic Crystals (PhCs) with orientable and arbitrarily large Chern vectors, in a reduced TRS broken environment. The strategy proceeds in two steps: formation of photonic Weyl points in a magnetic PhC, and their annihilation via geometric modulation on multifold supercells. The resulting crystals present the following novel characteristics: First, large Chern vectors can be obtained by design, making the PhC ideal for multi-modal operation. Second, full orientability of Chern vectors is achieved in the 3D space, opening up larger 3D CI/3D CI interfacing possibilities as compared to 2D Chern PhCs. Finally, non-zero Chern vectors can be achieved at reduced magnetization conditions, interestingly for photonic applications in the frequency regime where the magnetic response is weak.