Tunable higher-order non-Hermitian skin effect in the SSH topolectrical circuits.

Non-Hermitian systems reveal a wide range of fascinating physical phenomena beyond those found in Hermitian systems, drawing significant interest. Among these phenomena, the non-Hermitian skin effect (NHSE) is particularly notable. This effect enables the bulk states to collapse toward the boundaries and manifest as localized states. In this study, we report an experimental realization of a tunable higher-order NHSE in the Su-Schrieffer-Heeger (SSH) topolectrical circuits. Our experiments were conducted on specially designed one-dimensional and two-dimensional SSH tight-binding circuit networks. Two types of NHSEs with distinct angular localized modes (the diagonal distributed topological-skin mode and the isolated skin-skin angular mode) have been confirmed theoretically and experimentally. By controlling operational amplifiers and other electronic components, we could predict and tunable the skin effect modes in varying dimensions. The tunable NHSEs can be applied to guide waves into target regions, which can offer a number of valuable potential applications.