Boundary-Connected Higher Order Weyl Semimetals in a Helix-Shaped Phononic Crystal

The proposal of higher-order topology leads to intriguing wave propagation properties beyond the conventional bulk-boundary principle in condensed matter physics. Theoretical and experimental models have been conducted to reveal exotic higher-order hinge and corner states in lower dimensions. Meanwhile, this concept is extended to semimetals and verified in platforms like acoustic and photonic systems. However, most existing schemes are confined to C-n-symmetric-like frameworks. Here a phononic higher-order Weyl semimetal (HOWSM) is put forward by introductions of artificial gauge flux shape. Distinguished from most existing schemes, the traditional two-dimensional lattice with a vertical screw-extending operation is deformed, which guarantees the emergence of higher-order Weyl points. The invariant index is utilized to measure different phases between non-trivial topological and normal insulators visibly. Simulation results indicate that the structure supports robust hinge wave transmission in a piling sample. This work brings new approaches for constructing HOWSMs and enriches the potential applications in manufacturing high-performance acoustic devices.

Automated summary

The proposal of higher-order topology in condensed matter physics goes beyond the conventional bulk-boundary principle and leads to intriguing wave propagation properties. Exotic higher-order hinge and corner states have been revealed in lower dimensions through theoretical and experimental models. This concept has also been extended to semimetals and verified in acoustic and photonic systems. However, most existing schemes are limited to C-n-symmetric-like frameworks. In this work, a phononic higher-order Weyl semimetal (HOWSM) is introduced by deforming a traditional two-dimensional lattice with a vertical screw-extending operation, ensuring the emergence of higher-order Weyl points. The structure supports robust hinge wave transmission in a piling sample, providing new approaches for constructing HOWSMs and enriching potential applications in high-performance acoustic devices.