Observation of Geometry-Dependent Skin Effect and Directional Invisibility in Passive Viscoelastic Media

Non-Hermitian skin effect (NHSE) refers to the boundary localization of an extensive number of eigenstates and offers fascinating phenomena such as non-reciprocal responses and improved sensitivity. Although NHSE has been demonstrated in various experimental platforms, active components are usually required, hindering the applicability and miniaturization of the designs. Here we demonstrate NHSE in two-dimensional continuous viscoelastic media and show that it is geometry-dependent: skin modes vanish in systems with specific shapes but emerge in more general configurations. As an application, we show controlled reflection and transmission at different impurity geometries and demonstrate directional invisibility of elastic waves.