Stitching-induced asymmetric topological interface states and solitons in trimer lattices

The Su–Schrieffer–Heeger model serves as a model system for studying condensed matter physics, topological photonics, and topological circuits, supporting topological edge states with potential applications in quantum computing and logic transistors. The Su–Schrieffer–Heeger model can be further extended to multimer lattices, such as the trimer model. In conventional trimer lattices, edge-localized modes generally appear at both ends of the lattice, in contrast to the unidirectional edge states induced by Floquet modulation. Here, we demonstrate that trimer stitching enables the regulation and generation of interface states and topological edge states localized on a single side of the trimer lattice. Furthermore, by introducing Kerr nonlinearity, soliton solutions at lattice interfaces and edges are obtained self-consistently, and their stability is examined. These results suggest potential applications in photonic devices, such as optical switches.