摘要
Nonreciprocal interlayer coupling is difcult to practically implement in bilayer non-Hermitian topological photonic systems.In this work,we identify a similarity transformation between the Hamiltonians of systems with nonreciprocal interlayer coupling and on-site gain/loss.The similarity transformation is widely applicable,and we show its application in one-and two-dimensional bilayer topological systems as examples.The bilayer non-Hermitian system with nonreciprocal interlayer coupling,whose topological number can be defned using the gauge-smoothed Wilson loop,is topologically equivalent to the bilayer system with on-site gain/loss.We also show that the topological number of bilayer non-Hermitian C6v-typed domaininduced topological interface states can be defned in the same way as in the case of the bilayer non-Hermitian Su–Schrieffer–Heeger model.Our results show the relations between two microscopic provenances of the non-Hermiticity and provide a universal and convenient scheme for constructing and studying nonreciprocal interlayer coupling in bilayer non-Hermitian topological systems.This scheme is useful for observation of non-Hermitian skin efect in three-dimensional systems.
基金
supported by the National Natural Science Foundation of China(Nos.91950204,92150302,and 62175009)
Innovation Program for Quantum Science and Technology(No.2021ZD0301500)
Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(No.KF202114).
