Emergence of Exceptional Points in Periodic Metastructures With Hidden Parity-Time Symmetric Defects

We study the elastodynamics of a periodic metastructure incorporating defect pair that enforces parity-time (PT) symmetry due to judiciously engineered imaginary impedance elements - one having energy amplification (gain) and other an equivalent attenuation (loss) mechanism. show their presence affects initial band structure Hermitian leads formation numerous exceptional points (EPs) which are mainly located at edges where local density modes is higher. The spatial location PT-symmetric serves as additional control over number emerging EPs in corresponding spectra well critical non-Hermitian (gain/loss) strength required create first EP specific minimizes strength. use both finite element coupled-mode-theory-based models investigate these metastructures, time-independent second-order perturbation theory further demonstrate influence size on minimum band. Our findings motivate feasible designs for experimental realization elastodynamic metastructures.