Phononic Skyrmions: a new horizon to structure acoustic and elastic waves ?
Résumé
Skyrmion, a topologically stable three-component vector field, was initially developed in elementary particles and has since been demonstrated in condensed-matter systems. In this talk, I will report theoretically and experimentally on the existence of phononic skyrmions as new topological structures formed by the three-dimensional hybrid spin of elastic waves. Elastic phonons form an excellent platform for carrying and processing information due to their unique advantages, including orders of magnitude lower phononic wavelength in comparison with photonic systems 1 , scalability toward integrated devices 2 , and extremely low losses 3. The development of phonon physics has advanced the technology in high signal-to-noise information processing 3 , high-sensitive remote sensing, and intense wave-matter interaction for future quantum networks 4. Thus, in actual solid carriers with ubiquitous defects, realizing a new topological robust mode, i.e., phononic skyrmion, could lead to transformative phononic applications, especially in a generally concise configuration that can be scaled accordingly for future chip-scale technologies. Recently, the hybrid spin induced by mixed transverse-longitudinal waves, which is responsible for abnormal phenomena beyond pure transverse waves and longitudinal waves (i.e., acoustic waves), has been uncovered in the elastic phononic system 5. The hybrid spin can inspire strong spin-momentum locking of the elastic edge modes. However, the trivial topological invariant of the latter is not robust against defects 6. In this talk, I will describe how to construct a new nontrivial topological structure of ultra-broadband phononic skyrmions based on the three-dimensional hybrid spin of elastic waves. It should, however, be pointed out that the formation of phononic and photonic skyrmions comes from different spin textures, with the latter being based on transverse wave spin.
Domaines
Physique [physics]
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