Manipulating the topological phase of coupled modes in a plasmonic array via engineering near-field asymmetry: From zigzag arrangement to dielectric substrate

Photonic nanoparticle arrays that exhibit topologically nontrivial phases are often established by arranging nanoparticles in a lattice configuration in analog to the Su-Schrieffer-Heeger model. This design strategy is based on the principle that the optical interactions among the nanoparticles are predominantly dictated by the distances between them. However, these interactions are also significantly shaped by the near-field profiles of the nanoparticles. As an exemplary case, we examine a zigzag array of metallic ellipsoidal nanoparticles (ENPs) and illustrate how the topological phase of coupled plasmonic waves in such an array can be manipulated by controlling the orientation of the ENPs. More intriguingly, the near-field characteristics of the ENPs can be fine-tuned by the presence of a substrate, suggesting an alternative avenue for modulating the inter-particle interactions. We further show that topological phase transitions in both one-dimensional (1D) and 2D ENP arrays can be triggered by introducing a nearby dielectric substrate, while maintaining the original lattice structure unchanged. Our findings reveal a different mechanism for modulating the topological phases of nanoparticle arrays and provide a strategy that could be extrapolated to other photonic and classical wave systems, suggesting possibilities for the design and control of topological states in carefully engineered photonic systems.