Propagation and circulating modes of the reciprocal non-Hermitian skin effect
Phys. Rev. A 112, 053501 – Published 3 November, 2025
DOI: https://doi.org/10.1103/gqlb-qxkl
Abstract
The non-Hermitian skin effect (NHSE) is a novel localization phenomenon, in which all bulk states in a non-Hermitian system under certain conditions are localized at the edge of the system. Conventionally, most studies of NHSE have dealt with discrete lattice systems with nonreciprocal couplings. However, in recent years, NHSE in a reciprocal two-dimensional continuous medium, such as photonic crystal systems, has also been reported. In particular, we have previously shown that NHSE also occurs in two-dimensional uniform media. In such two-dimensional systems, skin modes propagate in a direction perpendicular to the localization direction and, in particular, they have the property of propagating in only one direction. In this paper, we show numerically an intriguing scattering phenomenon: when a scatterer is placed in the path of a skin mode, the scattering causes the skin mode to hop between opposing edges. In addition, we propose a unique method of generating circulating modes with orbital angular momentum (OAM) using this scattering phenomenon. Our work paves the way for more applications of NHSE as microsized optical devices manipulating or generating OAM.
