Experimental observation of topological phase transitions in a mechanical 1D-SSH model

Abstract In this work, we report the experimental observation of the topological phase transition in a mechanical one-dimensional topological insulator using the Su-Schrieffer-Heeger (SSH) model. Our mechanical system was composed of an elastic string with metallic masses emulating atomic sites and the intra- and inter-cell interaction strengths controlled by the distances, d 1 and d 2 respectively, between the masses. We observed a trivial phase with a band gap of ∼9.2 Hz ± 0.5 Hz for d 2 / d 1 = 3, while the metallic phase closed the gap, d 1 = d 2 , to be reopened in the topological phase as ∼8.7 Hz ± 0.5 Hz, for d 2 / d 1 = 1/3, with two edge states located inside the band gap at ∼15.6 Hz ± 0.5 Hz. Our experimental observations were supported with numerical and theoretical models. Our work creates the ability to study topological phase transitions in mechanical systems with materials available in any research lab and allows an understanding of phase transitions in a visual way.