Speaker
Description
Solitons are universal nonlinear excitations that appear in settings as varied as optics, water waves, quantum gases and superfluids [1]. While reduced models of soliton dynamics are well established, their validity and dynamical behaviour in strongly nonlinear regimes with frequent interactions remain largely unexplored experimentally. Progress has been constrained by the difficulty of simultaneously achieving precise control of dispersion and nonlinearity, together with the temporal and spatial resolution required for dynamical observations.
In this presentation, I will present the first realisation of acoustic solitary waves in integrated phononic waveguides. Using low-loss silicon nitride membrane waveguides, our platform exploits the interplay between waveguide dispersion and mechanical Kerr nonlinearity to generate `dark' solitons that persist over metre-scale propagation distances. The slow phonon velocity allows direct imaging of hundreds of dark soliton collisions---two orders of magnitude more than have previously been accessible, as well as soliton fission and the melting of a soliton crystal. Furthermore, the unprecedented dynamical resolution allows us to verify two long-predicted aspects of dark soliton behaviour: the existence of a collisional phase shift and two depth-dependent, topologically distinct collision regimes. Spontaneous solitary-wave formation from noisy backgrounds reveals the emergence of quantized phase slips (manifesting as spatiotemporal acoustic vortices) in a one-dimensional medium described by the nonlinear Schrodinger equation (NLSE).
These results not only illuminate fundamental nonlinear energy transport processes, but also show a path towards acoustic versions of soliton-enabled technologies such as frequency combs and mode-locked lasers, as well as low-power information processing.
[1] see e.g. Reeves, M. T. et al. Nonlinear wave dynamics on a chip. Science 390, 371–376 (2025).
[2] Hirsch, T. M. F. et al. Solitary waves in a phononic integrated circuit. Preprint at https://doi.org/10.48550/arXiv.2603.22898 (2026).
| I am the presenting author | Yes |
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