Chiral phononic crystals have attracted considerable attention owing to their low-frequency and broadband bandgap characteristics arising from the press-twist coupling. However, prior investigations predominantly interpret the bandgap mechanism through the inertial amplification effect, which fails to explain the physical origin of the absence of analogous bandgap features in certain chiral structures. Therefore, the present study draws an analogy with the Thomson scattering effect in electromagnetic waves to describe the longitudinal-torsional polarization coupling and bandgap formation mechanism in chiral phononic crystals. We theoretically elucidated the intrinsic relationship between longitudinal-torsional iso-frequency orthogonal polarization coupling and the inertial amplification coefficient, as is the relationship between mirror symmetry and destructive interference in the Thomson scattering-analogous effect. Furthermore, a diatomic chain model is established to reveal the mutual constraint rules governing the upper and lower bandgap boundaries, and to clarify the fundamental reason for the incompatibility between low-frequency and broadband bandgap characteristics. A rigid-flexible coupling design strategy is proposed to achieve decoupling and independent tunability of the upper and lower bandgap boundaries. This study provides a unique perspective on the physical mechanism of elastic wave manipulation in chiral phononic crystals and establishes a theoretical foundation for the design of low-frequency broadband structures.

Assistant Professor, School of Mechanical Engineering, Southwest Jiaotong University. Received the Ph.D. from the School of Mechanical Engineering, Xi'an Jiaotong University, under the supervision of Professor Chen Tianning and Associate Professor Zhu Jian. During the doctoral program, conducted joint research at the group of Professor Yang Yaowen at Nanyang Technological University, Singapore. Primary research focuses on the key technologies for low-frequency broadband acoustic stealth in high-end underwater equipment. Using chiral phononic crystals as the primary research subject, published 9 peer-reviewed journal articles as first author, and 1 has been selected as an ESI Highly Cited Paper; holds 3 granted invention patents and 1 pending disclosure. Supported by the China Postdoctoral Science Foundation, currently leads one general postdoctoral research project and two industry-sponsored horizontal projects with leading enterprises in the field.