Longitudinal topologically protected states in a one-dimensional mechanical topological insulator.

Topological insulators are a type of material that allow the existence of unidirectional currents at the quantum scale. These currents, called edge states, are unaffected by material imperfections, which make topological insulators an active research topic with potential applications in quantum computing. Protected edge states - analogous to the unidirectional current flow of electronic topological insulators - have recently been demonstrated not only with electrons, but also with photons, sound waves, and mechanical waves [1]. Using a well-known model of topological insulators known as the Su-Schrieffer-Heeger (SSH) model [2], we constructed a one-dimensional mechanical model of topological insulators that propagates longitudinal waves in a structure of periodic vertical slabs. Using additive manufacturing, we developed a structure based on slabs with varying thicknesses to act as springs and masses. We also used a mathematical model to predict a phase transition between the insulator, conductor, and topological insulator phases of our SSH model, with clearly defined edge states in the topological insulator phase.



[1] L. Thatcher et al 2022 Phys. Scr. 97, 035702

[2] W. P. Su, J. R. Schrieffer, and A. J. Heeger 1979 Phys. Rev. Lett. 42 1698–701