Observation of higher-order non-Hermitian skin effect

摘要: Hermitian theories play a major role in understanding the physics of most phenomena. It has been found only past decade that non-Hermiticity enables unprecedented effects such as exceptional points, spectral singularities and bulk Fermi arcs. Recent studies further show can fundamentally change topological band theory, leading to non-Hermitian topology skin effect, confirmed one-dimensional (1D) systems. However, higher dimensions, these remain unexplored experiments. Here, we demonstrate spin-polarized, higher-order effect two-dimensional (2D) acoustic metamaterials. Using lattice coupled whisper-gallery resonators, realize spinful 2D insulator (HOTI) where spin-up spin-down states are emulated by anti-clockwise clockwise modes, respectively. We find drives wave localizations toward opposite edge boundaries depending on spin polarizations. More interestingly, for finite systems with both corner boundaries, leads two bulk, spin-dependent manner. rich manipulation through loss configuration each unit-cell. The reported spin-dependent, reveals interplay between non-Hermiticity, which is enriched degrees freedom. This unveils new horizon study design