Demonstration of the Majorana-like bound state in an elastic bolted plate

With the unveiling of the topological non-trivial phases, abundant demonstrations of the bulk-boundary correspondence in various domains of physics have been conducted in recent years. More recently, higher-order topological insulators are realized to reveal not only the boundary states but also the zero-dimensional corner states. In this work, another uniquely zero-dimensional non-propagating state, specifically a mechanical analog of the Majorana bound state, is shown numerically and experimentally in a mechanical system. We implement topological binding by creating a Kekulé distortion vortex on a two-dimensional thin plate with local resonators mounted in a honeycomb arrangement. It is renowned that Majorana bound states are protected by particle-hole (PH) symmetry. Similarly, to show our mechanical Majorana-like bound state is insensitive to certain type of disorder, we design a local perturbation to mimic the PH symmetry. We confirm that the Majorana-like bound state is indeed robust against the PH-symmetric perturbations and maintains pinned to Dirac frequency of the undistorted lattices. We anticipate that this finding will enrich the topological non-trivial phases in bosonic systems and broaden the applications of the energy localization or energy harvesting.