Multiband topology in acoustic coupled Su-Schrieffer-Heeger chains

Multiband topology, as a unique feature of topological phenomena in classical wave systems, has attracted much attention owing to its potential applications in broadband topological devices. Here we study the multiband topology in a coupled two-chain Su-Schrieffer-Heeger model where the two Su-Schrieffer-Heeger chains with different hopping configurations are coupled via interchain hopping. We find that the topological transitions of different band gaps can be triggered by our tuning the interchain and intrachain hoppings, leading to a rich phase diagram with various multiband topological effects. Using acoustic metamaterials and pump-probe measurements, we confirm in experiments these multiband topological effects by observing the emergence and disappearance of the topological edge states in different band gaps, which are in excellent agreement with the theory. The findings here provide a promising way toward multiband topology with clean physics and richness, which can serve as a prototype case for understanding multiband topology.