Observation of the non-Hermitian Skin effect in topolectric circuits*

A contemporary frontier of metamaterial research is the challenge non-Hermitian systems pose to the established characterization of topological matter. There, one of the most relied upon principles is the bulk-boundary correspondence (BBC): energy eigenvalues and eigenstates exhibit a perturbatively small change as the boundary conditions are modified from periodic to open by changing a single bond. The framework of BBC captures the emergence of protected surface states at the boundary of a system with non-trivial bulk topology. In this talk, we present a periodic circuit network, where gain and loss conspire with the violation of reciprocity to affect this principle dramatically. Switching from periodic to open boundary conditions results in a non-perturbative change of all eigenmodes in this system. We experimentally observe the non-Hermitian Skin effect with extensive mode localization at open boundaries for the first time.

Reference: T. Helbig, et al. arXiv:1907.11562 (2019).