Topological Vibration Analysis of Elastic Lattices via Bloch Sphere Mapping

Abstract

Mechanical lattices support topological wave phenomena governed by geometric phases. We develop a compact Hilbert space description for one-dimensional elastic chains, expressing intra-cell motion as a normalized superposition of orthogonal eigenstates and tracking complex amplitudes as trajectories on a Bloch sphere. For diatomic lattices, this framework makes inversion symmetry protection explicit: the relative phase between in-phase and out-of-phase modes is piecewise locked, and the Zak phase is quantized with band-dependent jumps at symmetry points. Extending the analysis to triatomic lattices shows that restoring inversion retains quantization, whereas breaking it dequantizes the geometric phase while leaving the spectral origin invariant. Viewing norm-preserving transformations of the modal coefficient pair as Bloch sphere rotations, we demonstrate classical analogues of single-qubit logic gates. A pi-phase rotation about a transverse axis swaps the modal poles, and a longitudinal-axis phase flip maps balanced superpositions to their conjugates. These gate-like operations are realized by controlled evolution across wavenumber space and can be driven or reprogrammed through spatiotemporal stiffness modulation. Introducing space-time modulation hybridizes carrier and sideband harmonics, producing continuous phase winding and open-path geometric phases accumulated along the Floquet trajectory. Across static and modulated regimes, the framework unifies algebraic and geometric viewpoints, remains robust to gauge and basis choices, and operates directly on amplitude-phase data. The results clarify how symmetry, modulation, and topology jointly govern dispersion, modal mixing, and phase accumulation, providing tools to analyze and design vibration and acoustic functionalities in engineered structures.