2023/09/28 by Michael Fidelis Groß, Jonathan L. G. Schneider, Yi Chen +2 · 1 voice
Engineering · Materials Science · #Acoustic Wave Phenomena Research #Metamaterials and Metasurfaces Applications #Thermal Radiation and Cooling Technologies
paper · pdf · doi:10.1002/adma.202307553
openalex publication_date 2023/09/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
In many cases, the hybridization of two or more excitation modes in solids has led to new and useful dispersion relations of waves. Well-studied examples are phonon polaritons, plasmon polaritons, particle-plasmon polaritons, cavity polaritons, and magnetic resonances at optical frequencies. In all of these cases, the lowest propagating mode couples to a finite-frequency localized resonance. Herein, the unusual metamaterial phonon dispersion relations arising from the hybridization of an ordinary acoustical phonon mode with a back-folded soft or easy phonon mode of a monomode elastic metamaterial are discussed. Conceptually, the single easy mode can have strictly zero wave velocity. In reality, its wave velocity is very much smaller than that of all other modes. Considering polymeric three-dimensional printed elastic monomode metamaterials at ultrasound frequencies, it is shown theoretically and experimentally that the resulting pronounced avoided crossing, with a frequency splitting comparable to the mid-frequency, leads to backward-wave behavior for the lowest band over a broad frequency range, conceptually at zero loss.