Observation of mechanical kink control and generation via phonons

TL;DR

This paper reports the first experimental demonstration of phonon-mediated control and generation of topologically protected mechanical kinks in a metamaterial, overcoming the Peierls-Nabarro barrier and revealing unique kink dynamics.

Contribution

It introduces a topological metamaterial that enables deterministic phonon control of kinks, a significant advancement over previous stochastic observations in physical systems.

Findings

Successful experimental observation of phonon-controlled kink generation

Demonstration of a topologically protected kink requiring zero energy to move

Revelation of unique kink dynamics including long-duration motion and internal modes

Abstract

Kinks (or domain walls) are localized transitions between distinct ground states associated with a topological invariant, and are central to many phenomena across physics, from condensed matter to cosmology. While phonon (i.e., small-amplitude vibration) wave packets have been theorized to deterministically interact with kinks and initiate their movement, this interaction has remained elusive in experiments, where only uncontrollable stochastic kink motion generated by thermal phonons or dislocation glide by low-frequency quasi-static loading have been observed. This is partly because all physical systems that support kinks are, at some level, discrete, making deterministic phonon control of kinks extremely challenging due to the existence of Peierls-Nabarro (PN) barrier. Here, we demonstrate, for the first time, experimental observation of phonon-mediated control and generation of mechanical kinks, which we enable using a topological metamaterial that constitutes an elastic realization of the Kane-Lubensky chain model. Our metamaterial overcomes the PN barrier by supporting a single, topologically protected kink that requires zero energy to form and move. Using simulations that show close agreement with our experimental observations, we also reveal unique dynamics of phonon interplay with highly discrete kinks, including long-duration motion and a continuous family of internal modes, features absent in other discrete nonlinear systems. This work introduces a new paradigm for topological kink control, with potential applications in material stiffness tuning, shape morphing, locomotion, and robust signal transmission.