Elastic wave spin and unidirectional routing in thin rod systems

• Published in: International journal of mechanical sciences 2024-09, Vol.277, p.109512, Article 109512
• Main Authors: Zhang, Yuxuan, Zhao, Jinfeng, Huang, Yao, Yang, Chenwen, Yuan, Weitao, Zhong, Zheng, Ren, Jie, Pan, Yongdong
• Format: Article
• Language: English
• Subjects: Elastic wave; Elliptic polarization; Non-circular cross section; One-way transmission; Spin angular momentum; Thin rods
• ISSN: 0020-7403; 1879-2162
• DOI: 10.1016/j.ijmecsci.2024.109512

•Elastic spin is explicitly derived and experimentally observed for all basic modes in rods.•Unidirectional wave routing is observed due to spin-momentum coupling.•Asymmetric transmission of longitudinal mode requires extremely elliptical chiral source.•Spin-momentum coupling of torsional mode depends on cross-section warping effect. The unusual topology of elastic waves in continuum systems has been recently uncovered. Prominently, the spin of Rayleigh-Lamb waves has been experimentally observed and used to achieve the unidirectional wave propagation. In this work, the elastic wave spin in thin rod systems is theoretically predicted and experimentally observed, for all the three basic wave modes, i.e., the zero-order flexural, longitudinal and torsional modes. By elaborately building up the subwavelength chiral sources, the spin-momentum locking has been achieved for these three modes within broad frequency range. Interestingly and surprisingly, the spin-momentum locking occurs for flexural and longitudinal modes in both circular and non-circular thin rods; the spin-momentum locking for torsional modes only exits in non-circular thin rods, due to the warping effect in non-circular cross-section rods. Our results open up the door for elastic wave spin in thin rod systems, and provide general tips for the research on basic modes in diverse thin rods, based on either the continuum media or the artificial metamaterials in future. [Display omitted]