Observation of non-Hermitian topology and its bulk-edge correspondence in an active mechanical metamaterial

Understand

Topological edge modes are excitations that are localized at the materials' edges and yet are characterized by a topological invariant defined in the bulk.

• Such bulk-edge correspondence has enabled the creation of robust electronic, electromagnetic and mechanical transport properties across a wide range of systems, from cold atoms to metamaterials, active matter and geophysical flows.
• Recently, the advent of non-Hermitian topological systems---wherein energy is not conserved---has sparked considerable theoretical advances.
• In particular, novel topological phases that can only exist in non-Hermitian systems have been introduced.