Observation of phononic skyrmions based on hybrid spin of elastic waves.

Skyrmions with topologically stable configuration have shown a promising route toward high-density magnetic and photonic information processing due to their defect-immune and low-driven energy. Here, we experimentally report and observe the existence of phononic skyrmions as new topological structures formed by the three-dimensional hybrid spin of elastic waves. We demonstrate that the frequency-independent spin configuration leads to ultra-broadband feature of phononic skyrmions, which can be produced in any solid structure, including chip-scale ones. We further experimentally show the excellent robustness of the flexibly movable phononic skyrmion lattices against local defects of disorder, sharp corners, and even rectangular holes. Our research opens a vibrant horizon toward an unprecedented way for elastic wave manipulation and structuration by spin configuration and offers a promising lever for alternative phononic technologies, including information processing, biomedical testing, and wave engineering.