Searching for topological semi-complete bandgap in elastic truss lattices

TL;DR

This paper discovers a topological semi-complete bandgap in 3D elastic truss lattices, enabling the identification of topological degenerate points within a mostly complete bandgap, and demonstrates this experimentally.

Contribution

It introduces a systematic method to realize and map topological semi-complete bandgaps in elastic systems, advancing topological mechanics applications.

Findings

Identified a topological semi-complete bandgap in elastic truss lattices.

Experimentally mapped the nontrivial surface states within the bandgap.

Provided a new approach for engineering topological phases in mechanical systems.

Abstract

Gapless topological phases have attracted significant interest across both quantum and classical systems owing to their novel physics and promising applications. However, the search for ideal gapless topological nodes inside a clear bandgap is still lacking in elastic systems. The degenerate points are always hidden in the trivial bulk bands due to the intricate elastic modes involved. Here, we find a topological semi-complete bandgap in a three-dimensional elastic truss lattice by tuning a supporting rod, which exhibits a complete bandgap except for the inevitable topological degenerate points. Furthermore, we experimentally map the topological semi-complete bandgap and the inside nontrivial surface state arcs with a scanning laser vibrometer. The introduced scheme provides a systematic approach for the idealization of semi-complete bandgaps and thus may significantly advance the practical utility of topological phases in mechanical engineering domains.