Asymmetric near-zero edge mode in topological photonic lattice without chiral or particle-hole symmetries

Generally speaking, a one-dimensional system requires chiral or particle-hole symmetry to be topologically nontrivial. In this Letter, we show that topological behavior can also be observed in a quasi-one-dimensional photonic system without the aforementioned symmetries. The results indicate that the quantized Zak phase is achieved in such a system even though the chiral and particle-hole symmetries are still absent. Further study shows that the system can support a topologically protected asymmetric near-zero mode on the right edge. Our work enriches the concepts of design of topological photonics and may have important applications in future quantum computations.