Synthetic Kramers Pair in Phononic Elastic Plates and Helical Edge States on a Dislocation Interface

• Published in: Advanced materials (Weinheim) Vol. 33; no. 9; pp. e2005160 - n/a
• Main Authors: Liu, Ting‐Wei, Semperlotti, Fabio
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.03.2021
• Subjects: dislocation interface; Elastic plates; Engraving; helical edge state; pseudospin; synthetic Kramers pair; topological phononics; dislocation interface; synthetic Kramers pair; pseudospin; topological phononics; helical edge state
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202005160

In conventional theories, topological band properties are intrinsic characteristics of the bulk material and do not depend on the choice of the reference frame. In this scenario, the principle of bulk‐edge correspondence can be used to predict the existence of edge states between topologically distinct materials. In this study, a 2D elastic phononic plate is proposed with a Kekulé‐distorted honeycomb pattern engraved on it. It is found that the pseudospin and the pseudospin‐dependent Chern numbers are not invariant properties, and the ℤ2 number is no longer a sufficient indicator to examine the existence of the edge state. The distinctive pseudospin texture and the pseudomagnetic field are also revealed. Finally, the synthetic helical edge states are successfully devised and experimentally implemented on a dislocation interface connecting two subdomains with bulk pattern identical up to a relative translation. The edge state is also imaged via laser vibrometry. The topological origin of the “zone‐folding” phononic topological insulator is revealed and its interpretation as an analog to the quantum spin Hall effect is shown to present key differences in comparison with its electronic counterpart. Also, the possibility of realizing two counter‐propagating gapless helical edge states on a dislocation interface connecting two subdomains with bulk pattern identical up to a relative translation is shown.