We study a continuous phononic elastic structure capable of reconfigurable topological edge states. The occurrence of edge states is due to a mechanism that can be considered as the acoustic analogue of the quantum valley Hall effect. By assembling two lattices having broken space-inversion-symmetry we induce gapless edge states at the corresponding domain wall, that is the interface between the lattices. The spatial symmetry of the phononic lattice as well as the topological transition are controlled by an externally imposed strain field. The underlying physical mechanism controlling the propagation behavior in such phononic structure is investigated by a combination of theoretical analyses and numerical simulations. Results show that chiral edge states can be obtained at the domain wall and that the strain field enables their direct tuning. Although this approach produces only a weak topological material in which time-reversal symmetry is still intact, the edge states supported at the domain wall prove to be very robust against back-scattering, even in presence of strong lattice disorder.
Ting-Wei Liu and Fabio Semperlotti, "Inducing and tuning edge-states in a weak topological phononic waveguide," Proc. SPIE 10600, Health Monitoring of Structural and Biological Systems XII, 106001E (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 07, 2018; Published: 27 March 2018); https://doi.org/10.1117/12.2295741.
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