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Topological guiding of elastic waves in phononic metamaterials based on 2D pentamode structures

The study of topological states in non-electron based systems has made a flourishing development in recent years. However, compared to the steadily growing amount of topological works of acoustic waves in phononic systems, fewer works are focused on elastic waves in solid state devices due to increased difficulties in the control of the propagation of elastic waves and the higher requirements for actual fabrication. A topological state with protected propagation of elastic waves is demonstrated in this work by appropriately engineering a phononic metamaterial based on 2D pentamode structures in silicon. Elastic pentamode materials have been shown to exhibit interesting properties, in particular so called mechanical cloaking but studies regarding the possibility to sustain topologically protected wave transport have yet remained elusive. The propagation characteristics and their geometry dependent behavior in order to provide feasibility for actual applications have been explored. The scalability of our results and the mature fabrication processes available for silicon based systems render this an important possibility to fabricate tailored structures in different frequency regimes in particular higher frequencies reaching the GHz regime.    

Yuning Guo, Thomas Dekorsy, and Mike Hettich
Scientific Reports 7, 18043 (2017)
DOI: 10.1038/s41598-017-18394- 8